Ecologist's Notebook

Simple diagram of a virus. By domdomegg, Wikimedia Commons

(Click on the following link to listen to an audio version of this blog …. Viruses and the Birth of the Avian Flu

Viruses are very small. They are typically between 10 and 300 nanometers in size. Very few of us have an intuitive sense of what a nanometer is. It is very straightforwardly defined as one billionth  (10^-9) of a meter, but that really doesn’t give us much perspective on it either. An average cell in your body, which you recognize as being a very small thing in itself, is just under 100 micrometers in diameter (a micrometer is one millionth (10^-6) of a meter). Without dwelling on the math, by volume, one of your average body cells is a hundred million to a billion times bigger than a virus! So cells are small, but viruses are REALLY small!

Viruses are extremely simple. They have a core of a nucleic acid (either DNA or RNA) surrounded by a “capsid” made up of proteins that are then, in some viruses, further surrounded by “envelopes” of lipids that are studded with very specific glycoproteins.

Viral nucleic acids typically encode the information for 30 or 40 genes, and these genes represent the information needed for the synthesis of a variety of molecules including the components of the viral capsid and envelope. Viruses must utilize the metabolic machinery of a living cell to replicate themselves since they lack both energy generating systems and also the ribosomes needed for protein synthesis.

Diagram by B. Taylor. Wikimedia Commons

Of the 7000 or so species of viruses that have been described, only 200 affect humans. Viruses have to enter cells in order for their genes to be able to hijack the cell’s metabolic machinery and program it to make more viruses. Entering a cell is not an easy thing even for something as small as a virus. On a cell’s plasma membrane are numerous proteins that act as enzymes or channels or transporters for ions and molecules. Often, these membrane proteins are the doorways by which a virus enters a cell. The virus, though, has to fit very precisely into these membrane proteins in order to pass through them. Viruses that can pass through one species’ type of membrane protein might not fit through a similar protein of a different species. So, particular viruses usually only infect certain host species!

Flu viruses are very common, disease causing entities that can affect almost any species of birds or mammals. There are four types of influenza viruses: Types A, B, C and D. Only Types A and B can affect humans, and Type A is the most common influenza virus involved in human disease. Many other species of birds and mammals can also be affected by Type A influenza viruses, although I said above, usually each virus is relatively specific for a particular host species.

Flu virus. Diagram by Young and Lee. Iimedia Commons

The structure of a Type A influenza virus consists of eight individual RNA molecules that are each wrapped by capsid proteins. These RNA’s are grouped together and further wrapped with more matrix proteins and a phospholipid bilayer envelope. The envelope has two major glycoproteins on it: hemagglutinin (H) and neuraminidase (N).

Hemagglutinin (H) makes up 80% of the viral surface glycoproteins. It functions to match up with surface glycoproteins on host cells and, thus, allow the virus to attach itself to a potential host cell. The H’s, then, are critical in the initial steps of a virus matching up to a potential host. Specifically, host cell glycoproteins with sialic acid groups serve as the attachment points for the H glycoproteins. There are 16 types of H glycoproteins.

Neuraminidase (N) makes up the remaining 20% of a virus’s surface glycoproteins. Neuraminidase acts to remove sialic acid molecules from a newly synthesized virus’s envelope as it leaves its host cell.  This keeps the emerging viral particles from clumping together via their own H glycoproteins. Some N’s can also alter a host organism’s immune functions and can have impacts on interferon production and activity. There are nine types of N glycoproteins.

The strains of the Type A Influenza virus are classified according to the specific types of H and N glycoproteins that they possess. For example, “Spanish flu” (1918) is H1N1, “Asian flu” (1957) is H2N2, “Hong Kong flu” (1968) is H3N2, “swine flu” (2009) is also H1N1, and avian flu (1996 to present day) is H5N1.

TEM of avian flu virus (H1N5). Photo by CDC. Public Domain

H5N1 is defined as a “highly pathogenic avian influenza” (HPAI). It causes very serious disease in domesticated birds (i.e. “poultry”) and also certain types of wild birds (waterbirds like ducks, geese and swans, shorebirds, and hawks, eagles, falcons, owls, crows, vultures). These HPAI’s are seldom observed in the types of birds that frequent backyards and backyard bird feeders (robins, cardinals, blue jays, house finches, sparrows etc.), so throughout this avian flu outbreak removal of bird feeders and bird baths have not been required or even recommended.

H5N1 was first detected in China in 1996. Its initial impact was a very high death rate in bird populations on poultry farms. For its first 15 years, H5N1 was a seasonal infection whose occurrence was timed with the autumn migration of wild birds.  In 2021, however, H5N1 changed to become a persistent, year-round infection killing millions of birds across five continents (Europe, Africa, Asia, North America and South America).

Shorebirds (willets, marbled godwits and dowitchers). Photo by I. Taylor. Wikimedia Commons

H5N1 spreads between birds via their mucous, saliva or feces. Most viral spread is from bird to bird with bird to human transmission occurring only after direct, unprotected contact with infected birds or their wastes. Human infections can result from breathing in viral ladened air droplets or dust particles, or from touching surfaces contaminated with infected bird mucous, saliva or feces and then touching eyes, mouth or nose. Appropriately used personal protective gear (masks, gloves, goggles etc.) is quite effective at blocking these routes of infection. Human illness from H5N1 ranges from a completely asymptomatic state to severe illness which occasionally has resulted in death.

Viruses can borrow and mix their genetic materials quite freely. For example, in 2020, there was an outbreak of some “low pathogenic avian influenza” (“LPAI”) in 12 turkey farms in North and South Carolina. This LPAI strain, “H7N3,” probably would not have caused serious illness in the infected birds, but to control the spread of the infection, the birds at these 12 locations were killed (or “depopulated” (to use the term utilized in the reports and papers describing the outbreak)).

Domesticated turkeys. Photo by USDA. Public Domain

Following this controlled “depopulation,” though, new outbreaks of an altered strain of H7N3 were observed in South Carolina, and the symptoms in these infected turkeys were so severe that this new strain was classified as an “HPAI.” Tracing this virus through a range of turkey farms resulted in the “depopulation” of 361,000 turkeys.

Apparently, what had occurred in these isolated populations of turkeys was the intermingling and intermixing of the genetic material from several viral strains that were simultaneously infecting the birds. The RNA from the LPAI H7N5 was shuffled together with RNA from a variety of LPAI flu strains  that probably originated from wild birds. The resultant H7N3 strain was then highly pathogenic and extremely dangerous.

This same process of viral, genetic recombination occurred in a poultry population somewhere in Europe in 2021. The new strain of H5N1 which arose from this genetic re-scrambling then spread and caused the ongoing avian flu epidemic. In this European event, like in the case of the sick turkeys in the Carolinas. a population of poultry was simultaneously infected with a very common flu strain (H5N8) and several varieties of wild bird LPAI. The resultant recombination was an HPAI H5N1 with an N1 derived from wild birds. This new H5N1 was extremely contagious, persistent and virulent.

Global spread of H5N1 among wild and domesticated birds. Dark red indicates human infections, too. Wikimedia Commons

Two subtypes of this new HPAI H5N1 arose in 2021 and 2022. One spread to the coastal regions of Central Europe and was carried across the Atlantic Ocean by migrating birds. The second strain spread around the Mediterranean Sea and down into Africa. In 2022, these two H5N1 strains killed millions of birds in Europe, Africa, Asia and North and South America. The virus also began to infect a growing array of mammals including human beings!

Next week: avian flu affecting the rest of us!

Photo by D. Sillman

(Click on the following link to listen to an audio version of this blog … Wild sunflowers

The first full summer we were in our new house in Greeley we changed the landscaping of our yard considerably. In April, we hired someone to come in and remove the water-hungry bluegrass and fescue lawn. We then divided the front yard into two sections. We then divided one of these sections into asymmetrical geometric areas with arcing rocky pathways (“dry stream beds”) and cindered walkways. We then built brick-walled, planting circles in between the paths and walkways and put down mulch to fill in the spaces outside the planting circles. In the other section of the yard we planted in a mix of buffalo and blue grama grasses (the historical mix of the shortgrass prairie) and watered and weeded it through the summer. The grass came in very patchy, so we re-seeded in June and  had, by the end of summer, a decent cover layer of grasses. The weeds flourished in the broken soil and abundant moisture! Weeding was a daily task!

Also in this first summer, four, robust, volunteer patches of wild, common sunflowers (Helianthus annuus) grew up in the mulched areas of the yard. These sunflowers self-seeded probably from bird transport in the previous summer or fall) from plants growing along nearby roadsides and field edges. The sunflowers grew quite tall (6 to 8 feet) and made large, seed-filled flower heads. Seeds from these 2021 sunflowers, then spread and germinated all across the yard so that in spring 2022 and we had hundreds of wild sunflowers growing in the front yard.

Photo by D. Sillman

The rate of growth of these plants was astonishing! I have photographs of the front yard in mid-June 2022 in which there are no sunflowers in sight and then, three weeks later, the same view now dominated by a dense, sunflower jungle! We were forced to thin the sunflower plants very aggressively in order to have room for our other front yard plants to grow!

When these sunflowers were young and growing so rapidly, we watched them exhibit the property of “heliotropism.” At dawn, the entre yard of sunflowers had positioned their developing flower heads to face the east and the rising sun. They then, through the day, slowly turned their flower heads to follow the sun across the sky until at sunset, they were all facing to the west and the setting sun. Only the young sunflowers exhibited this behavior, though. The older, mature sunflowers positioned their flower heads toward the east and kept them there.

One explanation of this interesting behavior is based on the previously mentioned rapid growth rate of the sunflower stems. Apparently, during the day, the cells and tissues on the east side of the stem grow more rapidly than those on the west side, thus turning the sunflower head to the west. At night, the cells and tissues on the west side of the side of the stem grow more rapidly, thus turning the sunflower head back to face the east. By the time the sunflower is fully grown, though, these stem cells and tissues have stopped growing and the heliotropic behavior ceases to occur!

Photo by D. Sillman

The pollinators loved the sunflowers! There were clouds of buzzing insects around the flowerheads from the end of June well into August! Sunflowers are an important source of nectar and pollen for these insects and help to sustain these vital organisms through the summer season.  Deborah did a visual census of these sunflower pollinators and observed honeybees, bumblebees, several species of solitary bees, multiple species of flies, several kinds of beetles, damselflies and more! Talk about a keystone species!!

Common sunflowers are one of five native, sunflower species found here in Colorado. The other four native species include the Maximillian sunflower (H. maximilanii) which grows all over the Americas in dense clumps of ten foot-tall stalks, the Nuttalls sunflower (H. nuttalii) which grows primarily in the damper regions of the nearby foothills of the Rocky Mountains, prairie sunflowers (H. petiolaris) which make relatively low, branching sunflower-bushes especially along roadsides that cut through the Colorado plains, and bush sunflowers (H. pumilus) which primary grow on dry hillsides.

Common sunflowers (H. annuus) are the wild stock from which Native Americans some 3000 years ago derived the larger seeded, domesticated sunflower which they then grew extensively across North America for human consumption. Some scientists think that these cultivated sunflowers were actually developed for human food even before corn! These native American sunflower varieties were exported to Europe in the 1500’s (in that great, post-Columbian shift of plant species back and forth across the Atlantic Ocean!), and then they were further developed into the large flower/large seed varieties that are currently grown around the world for human consumption, oil, and livestock and wild bird feed.

Male and female American goldfinches. Photo by K. THomas. Wikimedia Commons

Starting in late September, birds (house finches, chickadees and house sparrows) swarmed the flower heads and gobbled down the tiny seeds. Several fox squirrels also climbed up the two and a half inch thick sunflower stems and pulled whole flowers off of the plant to eat the seeds. Then one day in early October, a flock of goldfinches (a bird I had not seen all summer) descended on one of the sunflower patches. The adult goldfinches pulled seeds out of the dry flower heads while a large number of their recent fledglings peeped and fluttered at them demanding to be fed. One reference that I consulted stated that the late summer reproduction timing of goldfinches is primarily driven by the late summer abundance of wild sunflower seeds!

In late summer, the plants quickly lost their brilliant luster and turned brown with the coming fall. They were not very attractive out in the front yard but were feeding so many animals in the yard that we decided to leave them in place until they have been stripped bare of seeds. A prodigious number of seeds fell off of these 2022 plants and caused an even bigger sunflower explosion in 2023! Left alone, it seems that the whole world would be covered with sunflowers!

The dried, sunflower stalks were very difficult to remove! Some were so thick and woody that I had to use a chain saw to cut them down, and their roots were so deep and dense that it took many minutes and lots of effort to dig each stump out! After repeating this laborious process in 2023, we decided that we had to limit the sunflowers that we allowed to grow in our yard.

Starting in early spring 2024 Deborah pulled hundreds or possibly thousands of sunflower seedlings out of the mulch, gravel, and planting rings of the front yard. From late April to mid-June this culling went on daily. Bucket after bucket , tub after tub and trash can after trash can of sunflower seedlings went out to the curb for pickup and transport to the landfill.

Maximillian sunflowers on the move! Photo by D. Sillman

Keeping the sunflowers under control has allowed other volunteer plants to come into our yard. Wild violas (“Johnny-jump-ups”), black-eyed Susans, brown-eyed Susans, Rocky Mountain prickly poppies, Russian sage, blanket flower, native coneflowers, salsify, fleabane, cornflowers and milkweed are all self-thriving in their corners of our mulch and gravel. The Maximillian sunflowers that we planted in one of the panting rings, though, have started to spread across mulch. What is it about sunflowers wanting to take over the world?

Northern saw-whet owl. Photo by Sage Wikimedia Commons

(Click on the following link to listen to an audio version of this blog … Saw-whet owl

One afternoon in the Fall of 1993, I was working in my office at Penn State New Kensington, when a student came in and told me that she had seen a “baby owl” hiding in the bushes under the entrance ramp to the front door to the Administration building. It was puzzling that a “baby” owl would be around in the Fall of the year. All of the Spring owlets should be grown and mostly fledged by now.

I went with the student and saw the “baby” owl. It was really a full-grown saw-whet owl  (Aegolius acadicus), and, amazingly, she was absolutely unruffled by the my presence or that of the student (or even by the parade of curious students who came down to se why their biology professor was sitting on the ground under the entrance bridge!

The saw-whet owl’s unusual name is derived from the sound of its calls. These calls have been variously described as resembling the sound of water dripping into a half-filled pail or the pinging that is generated when a saw blade is being sharpened (or “whetted”). The northern saw-whet vocalizes only during its breeding season (March to May) and uses its song both to attract mates and to mark its breeding territory.

Photo by G. Schechler. Wikimedia Commons

The northern saw-whet is the smallest owl found in the eastern half of the United States. Its range extends from the forests of the northeast, around the Great Lakes, across most of Canada, into Alaska, and southward down the line of the Rocky Mountains and the western coastal states. A year-round population of northern saw-whets is also found in the mountains of central Mexico. In Pennsylvania, the saw whet owl is a year-round resident in the northern tier of the state and a regular migrant through the southern part of the state and also into the adjacent states to the east, west and south.

It used to be thought, according to Jennifer Ackerman (in her book What an Owl Knows) that saw-whet owls were extremely rare and decidedly non-migratory. Both of the certainties, though, have been shown to not be true. Saw-whet owls are very small, obligatorily nocturnal, quite reclusive and very well camouflaged, but if a researcher very carefully searches through a prospective saw-whet habitat (dense forests and shrublands) they will find that they are surprisingly abundant.

Further, serendipitous observations especially around the Great Lakes have revealed mass, seasonal migrations of saw-whet owls which are especially large every four years or so. Mist net trapping across these migration zones confirms the episodic saw-whet owl migration patterns and has, interestingly, revealed that male saw-whet owls are much less prone to migration than female saw-whet owls.  This sex-specific migration strategy allows the females to seek out more southern, prey-rich habitats in the winter so that they can fatten up for the rigors of reproduction, but leaves the males near their optimal breeding territories which they quickly reclaim in the Spring.

Photo by B. Lally. Wikimedia Commons

Mist net trapping of migrating saw-whet owls in Pennsylvania over the past 26 years have captured 12,000 individual owls. Of these, only 12 have been males! (This is one of the reasons why I believe that the saw-whet owl hiding in the campus bushes in the Fall was a female!)

The northern saw-whet owl is 7 or 8 inches tall and weighs between 80 and 90 grams (2.8 to 3.2 ounces), Female owls tend to be 25% larger than males. The saw-whet is brown with a white, red-brown streaked belly. Their large yellow eyes are topped by a V-shaped white patch and surrounded by white facial disc that blurs laterally into brown. They have black beaks and brown and white speckled crowns.

Like most owls, the saw-whet is nocturnal and tends to be most active just after dusk and near dawn. It spends the daylight hours roosting on low branches in dense forests or shrub lands. It relies on camouflage for its safe concealment and if approached by a human typically reacts by maintaining its position and immobility. This behavior has led many people (and bird field guide authors) to describe these ferocious little owls as “tame.”

Photo by Scorpion 0422. Wikimedia Commons

This extremely docile behavior by saw-whet owls is a frequent observation made by almost everyone who comes into contact with them. Behavioral scientists explain this apparent tameness as the extension of the owl’s basic survival strategy in the wild: when faced with a threat they remain very still and rely on their camouflaging coloration to prevent detection. They shut down their aggressive natures to try to hide and, hopefully, survive. Owl experts speculate that that a saw-whet owl is actually under considerable stress when it is in close proximity to a human. Their innate behavioral wiring, though, causes them to appear placid and calm.

The saw-whet is an active hunter that takes deer mice (Permyscus leucopus) for 66% of all of its prey. Meadow voles and shrews also make up significant percentages of prey taken. They also consume song birds and locally abundant prey species like the intertidal and shoreline crustaceans on islands of British Columbia.

Northern saw-whet owlets. Photo by Kathy and Sam. Wikimedia Commons

The northern saw-whet breeds primarily in densely forested sites. Northern coniferous forests, thickets of secondary successional forest growth, and shrub lands are common habitats in which these owls can nest and reproduce. Nests are constructed in both naturally occurring tree holes and abandoned nest holes made by large woodpeckers (like the pileated woodpecker). They also will nest in artificial nest boxes. Nest sites near water are highly favored. Females typically lay 5 or 6 white, oval eggs and then will, with only occasional short trips away from the nest for defecation or pellet regurgitation, continuously incubate the clutch for 21 to 28 days. During this incubation period the male will bring the female food but will not actually participate in the nest brooding. There have been observations of males caring for more than one female on nests at one time, but this must have occurred in habitats with very abundant food supplies.

The females remain in the nest and keep the tree hole very clean during the incubation period and through the first 2 ½ weeks of the nestlings’ lives.  The owlets grow very rapidly, though, and 18 days after egg hatching, the female begins to roost outside of the tree hole. In the next 2 weeks before the owlets fledge the nest cavity will steadily fill with feces, rotting pieces of uneaten prey, and regurgitated pellets. Survival of the entire cohort of nestlings depends on the local abundance of prey. If prey densities are limiting, the younger, latter hatching owlets will not survive.

Male northern saw-whet owl. Photo by Perenozvich. Wikimedia Commons

The fledged owlets roost together near the brood nest for the next 4 weeks. During this period of time they are fed, primarily by the male. During this period of time the female, liberated from the maintenance duties of her brood, may mate with another male and begin the rearing of a second clutch of eggs.

The saw-whet utilizes its excellent senses of vision and hearing to locate prey. Typically, the owl will perch on a low branch and opportunistically swoop down and take whatever prey it happens to detect below it. Its sharp talons efficiently grab and quickly kill most of the prey species it encounters. As mentioned before, deer mice are its overwhelmingly most abundant food. During cold weather, the saw-whet may cache extra kills in tree holes where they can remain frozen and preserved for many months. Before consuming these cached food items, the owl will warm them with its body (almost like it was incubating eggs!). Adult deer mice and comparably sized prey are torn into two pieces and usually eaten at two different meals. The small saw-whet cannot easily swallow its prey whole.

Deer mouse. Photo by G. Smith. Wikimedia Commons

Like all owls, the saw-whet relies on intestinal enzymes to break down the digestible body parts of its food. The un-digestible hair, bones, claws, feathers, or arthropod exoskeletons are then regurgitated in the form of a pellet. Examination of these pellets is an excellent way to access the specifics of an owl’s diet.

The northern saw-whet owl is a widely distributed and relatively common species throughout large sections of North America. Its small size, excellent camouflage, and preference for relatively unmanaged habitats, though, make its sighting an uncommon experience and, so, many bird guides list it as an uncommon species.  As long as complex woodland habitats are maintained, however, the saw-whet owl will continue to liven spring nights with its calls and help to keep wild deer mice populations under control. Migration data, though, indicates that that the large eruptions of saw whet owls that occur every four years or so are declining in magnitude. Habitat loss, climate change and declining prey availability have each been proposed as factors in the decline of the saw-whet owl.

Adult black legged tick. USDA. Public Domain

(Click on the following link to listen to an audio version of this blog …. Lyme disease and vaccines

One of the things I don’t miss about Pennsylvania are the ticks and the tick-bourn diseases like Lyme disease. Colorado does not have the ticks that carry the bacterium that causes Lyme disease. We have other things to worry about, but that would be the topic of another blog.

For many years, Pennsylvania has led the nation in the number of Lyme disease cases. Between 1990 and 2021 Pennsylvania had, according to the CDC, 142,264 reported cases of Lyme disease. Only New York State came close to PA in terms of numbers of people affected by this extremely serious illness. New York reported 138,585 cases between 1990 and 2021. These numbers, as high as they seem, are probably gross underestimates, and each year the total number of Lyme disease cases exponentially increase. The CDC estimates that almost half a million people get Lyme disease each year and only a very small percentage seek medical help and get accurately diagnosed.

Distribution of Ixoides scapularis. Public Domain.

The vector for the transmission of the bacterium (Borrelia burgdorferi) that causes Lyme disease is the black-legged tick (Ixodes scapularis) (formerly called the “deer tick”). The black-legged tick is a small, common tick found throughout the northeastern and north-central United States. This tick is also the transmission vector for a number of other bacterial and viral pathogens.

The life cycle of the black-legged tick can involve combinations of over one hundred different potential hosts (fifty-two different species of mammals, sixty species of birds, and eight species of reptiles) and can stretch out over a two or even a three year period with staggered emergences of different instar stages during different months of the year. Also, early instars of this tick are extremely small and difficult to see!

Black legged tick life stages. California Dept of Public Health. Flickr

Black-legged tick eggs are deposited in the fall in low, grassy or scrubby vegetation and hatch the next summer into the very small, six-legged larva life forms. These tiny ticks typically seek out small hosts (white-footed mice (Peromyscus leucopus) seem to be the preferred host for this life stage) but are able opportunistically to attach to larger mammals, too, including humans. These larva, though, are not born with any of the pathogens associated with Ioxdes scapularis and are, thus, unable to transmit any of its diseases (a small piece of good news!). If these larvae feed on a host that is carrying one of I. scapularis’ bacterial or viral pathogens, though, that tick will become infected with that disease-causing agent and will carry it and be able to transmit it throughout the rest of its life cycle.

After the larva has taken its blood meal, it molts into the larger, eight-legged nymph life form. This molt is often delayed until the following spring. These nymphs, then, seek a host for their blood meal. These hosts are usually mammals ranging in size from white-footed mice to dogs to cats to deer to humans. Because of the timing of this nymph emergence (May and June in much of the eastern United States), the spring is a time of great risk for ticks bites (and disease transmission) for humans!

After the nymphs have taken their blood meals they molt into adults. These adults are especially abundant in the fall. These much larger ticks typically attach to large mammals. The female adult ticks take a blood meal from their hosts and then use the energy from this feeding to make eggs. The adult male ticks attach to the same hosts, but do not feed (and, therefore, do not transmit pathogens at this stage). They are there to find a female and to mate! The males die shortly after mating and the females die after dropping off of their hosts to lay their eggs in the grassy and scrubby vegetation. Those eggs then overwinter and hatch in the summer to start the life cycle all over again.

Winter, Upstate New York. Photo by Antepenultimate. Wikimedia Commons

So why have the number of Lyme disease cases increased in the past few decades? Media reports stress the “common sense” inference that our increasingly warm winters (possibly due to climate change) are leading to increased survival of the ticks and increased spring and summer populations. Unfortunately, scientific research does not support this logical connection. A study published in 2012 in the Journal of Medical Entomology clearly showed that in spite of “common knowledge” to the contrary, cold winters (and they used Upstate New York as their cold winter site!) do not reduce the numbers of overwintering black-legged ticks. The ticks just have too many adaptations for cold tolerance and too many protected microhabitats available for even the brutal winter temperatures of New York State to have any effect on them at all.

White-footed mouse. Photo by DGE Robertson. Wikimedia Commons

Most researchers looking at these ticks attribute their increases to increases in the most critical host in the black-legged tick’s life cycle: the white-footed mouse. Fragmentation of forest habitats and the optimal conditions of suburban ecosystems for these mice along with significant declines in their natural predators have led to great increases in their numbers. Black legged ticks, then, in their larval and nymphal life stages are increasingly likely to find a white-footed mouse on which to feed and are, therefore, increasingly likely to survive to the next instar level. White-footed mice are also significant reservoirs for the Lyme disease bacterium, so the ticks have a higher probability of assimilating and then passing on these bacteria.

Weather and climate factors can have an impact on populations of white-footed mice, but it is not temperature that is the most important weather/climate feature but precipitation. Wet and humid conditions favor the growth of the plants upon which white-footed mice feed and thus can lead to increased population sizes. More white-footed mice means that nymphal black-legged ticks have an increased chance of finding its ideal “blood meal” host thus increasing the numbers of later instar stages.  Further, right after a black-legged tick has taken its blood meal its ability to control its body water concentration is greatly impaired. A tick, then, right after a blood meal is very likely to die if it encounters a dry environment. Increased precipitation and relative humidity, then, also favors survival of the tick!

Red fox (Vulpes vulpes). Photo by K. Billington. Wikimedia Commons

In a study published a  few summers ago in the Proceedings of the Royal Society B the presence of active mice predators (foxes, martens, weasels etc.) did not significantly reduce local populations of mice. The presence of these predators, though, did reduce the number of ticks each mouse had on them (a 90 to 95% reduction!) and also reduced the number of ticks that were carrying the B. burgdorferi bacteria (a 96% reduction!). Speculating on these findings, the study’s lead researcher, Dr. Tim Hofmeester, felt that the presence of the predators curtailed the movements of the mice and acted to disrupt the proliferation and spread of the ticks and, possibly, their intra-specific exchanges of the bacteria!

Stop Lyme disease by adding foxes and weasels (and how about coyotes?) to our fields and woods and neighborhoods? Works for me!

Gedi and Heidi. Photo by M. Hamilton

Dogs are also affected by the bacterium that causes Lyme disease. Lyme infections in dogs can lead to debilitating limb paralysis and occasionally fatal kidney failure. The good news for dogs is that there is a vaccine that effectively generates immunological protection against B. burgdorferi infections and also reduces the severity of the Lyme syndrome if an infection does get established. The very puzzling part of any discussion about this dog vaccine, though, is the realization that there is not a human, anti-Lyme vaccine currently available to help control this growing epidemic of human Lyme disease.

Making this vaccine story even more opaque is the realization that there exists not just one but two human anti-Lyme vaccines! One of these was actually available to the public about thirty years ago and the other one passed through clinical trials but was never released for general distribution.

Both of these vaccines, released at a time when Lyme disease was a relatively limited, localized problem, encountered a public relations buzz saw driven by superstition and anti-science bias. A small group of people claimed that the vaccine caused paralysis (no clinical evidence supported this). This group threatened legal action against the pharmaceutical company that had released the vaccine and also mounted an extremely effective misinformation campaign against the vaccine. Under the weight of these attacks and under threat of skyrocketing legal costs, the small pharmaceutical company that made the vaccine stopped manufacturing it, and the second pharmaceutical company decided never to release their vaccine. In the 1990’s when the vaccine was initially released the number of Lyme cases in the United States were much lower than today, so there was little economic incentive for the pharmaceutical company to continue to make the vaccine..

Photo by Intropin. Wikimedia Commons

There are two new vaccines being developed to protect humans from Lyme disease: Penn Medicine has designed an mRNA vaccine (the same kind of vaccine that was developed against SARS-CoV2). This vaccine is in preclinical testing stages, and Pfizer and Valneva have designed a protein vaccine that is currently entering human testing. Pfizer hopes that this testing will be completed by 2025 and the FDA approval process will be able to begin in 2026.

Lyme disease has caused a great deal of human misery, and this suffering is increasing every year! We need these vaccines (or we all need to move to Colorado!).

Remember, your best defense against Lyme disease is a “tick check” after any potential tick exposure. The ticks may be anywhere that white-footed mice might live (yards, fields, woods, etc.). The ticks have to be attached to you for 36 hours before they can begin to transfer the Lyme bacterium. Use a tick puller and dispose of the tick in a creative manner (drown them in alcohol or flush them down the toilet). Don’t let the threat of ticks keep you from the woods or hiking trails!

Northern spotted owl (female). Photo by K. Perensoviche. Wikimedia Commons

(Click on the following link to listen to an audio version of this blog … Spotted Owls and Barred Owls

I remember the conflict very well. The back and forth in the late 1980’s of charges and countercharges between logging interests of the Pacific Northwest and ecologists and environmentalists from all over the country. The debate: should the logging of the old growth forests of the Northwest be halted to save habitat for the northern spotted owl (Strix occidentalis caurina)? It was a vicious debate.

I had a biology colleague who stated emphatically that since the northern spotted owl was “just” a subspecies (with two other subspecies that were not, at that time, under threat of extinction) the Endangered Species Act didn’t apply to it. I am not sure how he reasoned that out exactly, but I think that his fundamental political point of view was bubbling up through his loose grasp of the biological facts and logic. The Endangered Species Act clearly states that any species or subspecies that is in decline may be considered for Act listings and protections.

Anyway, in 1990, the northern spotted owl was placed on the endangered species list, and in 1991 a sweeping federal judge’s ruling removed 24 million acres of federally controlled land from possible logging. In effect, this ruling ended timber harvesting in the Northwest (an activity that had been in decline for years). The spotted owl’s habitat was saved. It has been said that no other single animal species has had such a huge impact on land use, environmental policy and economics.

California spotted owl. Photo by USFWS. PUblic Domain

The three subspecies of spotted owl are distributed across the western edge of North America. The northern spotted owl is found primarily in the mature forests of British Columbia, western Washington, Oregon and down into the mountains of northern California. The California spotted owl (S. o. occidentalis) is found in the southern Cascades and western Sierra Nevada mountains and in isolated mountains down through California to Baja California. The Mexican spotted owl (S. o. lucida) is found in the southwestern United States (Utah, Colorado, Arizona and New Mexico) and western Mexico

Mexican spotted owl. Photo by G. Smith. Flickr

In the intervening 35 years the California and Mexican subspecies of the spotted owl have both declined precipitously primarily due to habitat loss. The Mexican spotted owl is now also listed as “threatened,” but the California spotted owl has not yet gained any official extinction designations.

The northern spotted owl is a medium-sized owl. It is 16 to 19 inches long and weighs from one to just over one pound. Its wingspan is 42 inches. In the northern-most part of its range, it is found in a very

Northern spotted owl. Photo by BLM. Public Domain

specific type of habitat: old growth forests especially old growth at relatively high elevations. It is considered one of the indicator species of old growth forest ecosystems! In the southern sections of its range, this habitat specificity is less narrow and these owls can be found in mixed forests although still primarily at higher elevations. The northern spotted owl’s diet is also extremely specific. It eats small mammals (90+% of its diet) especially northern flying squirrels (Glaucomys gabrinus), wood rats (Neotoma fuscipes and N. cincera), red tree voles (Arborimus longicaudus), western red-backed voles (Clethnonomys californicus) and gophers (Thomomys spp.).

The setting aside of what was left of the old growth forests of northwest was at first thought to be sufficient to provide the northern spotted owl with enough space and resources to survive. Further fragmentation of these pieces of old forest, though, and their significant loss due to wildfires have made this simple picture look untenable. Also, the impact of a second owl species, the barred owl (Strix varia) has greatly complicated the survival model for the northern spotted owl).

Barred owl. Photo by P. Burian. Wikimedia Commons

The barred owl is the second most abundant and the second most widely distributed owl in North America. Only the great horned owl (Bubo virginianus) is more numerous and has a more extensive North American range. The barred owl is 16 to 25 inches long with a wingspan up to 49 inches. Male, barred owls weigh in between 1.3 and 1.5 pounds and females barred owls are 1.7 up to 2.5 pounds. The barred owls, then, are substantially larger than spotted owls.

The barred owl is native to eastern North America and is especially found in mature, eastern forests. It eats a very wide range of prey including numerous small mammals (its preferential food), but also readily takes small birds, amphibians, reptiles, bats, large insects, earthworms, fish and crayfish.

Distribution of barred owl. Map by Cephas-Mazur and James. Wikimedia Commons

There is an interesting, westward extension from the barred owl’s eastern range that seems to loosely follow the riparian forests and, possibly, human planted trees and wood lots that dot the former, northern prairie from western Ontario across Manitoba, Saskatchewan and Alberta all the way over to British Columbia. Within this expansion corridor, barred owls have been observed for over 150 years. In the vast, old growth forests of British Columbia the barred owl found an idea, forest habitat and, because of its larger size, aggressive nature and ability to take such a wide range of food, has out-competed many other owl species including the northern spotted owl.

Observations on these western barred owls has shown a number of behavioral differences between them and the eastern forest barred owls. These western barred owls do not preferentially inhabit dense, old growth forests. They are frequent residents of secondary and even fragmented forests. These western barred owls are also preferentially found near water. Lower elevation, riparian forests are their primary habitats. Further, genetic analysis of these western barred owls indicates that they have been separated from the eastern barred owls for thousands of years, not the few hundred suggested by the human-assisted irruption hypothesis. There is some doubt, then, about the validity of the barred owl being classified as an “invasive species” in these western forests. They may have been living in these forests for centuries.

Jennifer Ackerman in her book What an Owl Knows describes the interactions between northern spotted owls and barred owls. The very territorial barred owls zero in on the calls of the spotted owls and physically, sometimes lethally, interact with them. In the northern sections of the spotted owls range where the barred owls numbers are quite high, the spotted owls call to each other less and less. It is like they are hiding from the barred owls. In the middle and southern regions of the spotted owls range, though, where the barred owl densities are relatively low, the spotted owls continue to call to each other and, in the words of one of the scientists studying these owls, “seem to have decided to put up a fight for their territory.”

The U. S. Fish and Wildlife Service (FWS) has the legal responsibility to protect endangered species like the northern spotted owl. Ten years ago, the FWS killed 3600 barred owls in an attempt to reduce their influence on the northern spotted owl population. The FWS describes the outcome of this lethal experiment as “slowing down but not stopping” the barred owl mediated decline in the northern spotted owl.

Barred owl. Photo by L. Koester. Wikimedia Commons

In November, 2023 the FWS published a new plan in which they proposed to kill 500,000 barred owls over a three decade time span in order to ensure the survival of the northern spotted owl and the California spotted owl. Reactions to this proposal from scientists and the public have been overwhelmingly negative.

Is it ethical to kill one species to possibly save another? Is this barred owl extermination plan even possible? Wouldn’t removing barred owls from one part of a forest just result in the influx of barred owls from adjacent habitats? How long would this slaughter of barred owls have to go on to generate a safe space for the spotted owls?

There are some owl specialists who feel that the habitat selection preferences of the northern spotted owl (high elevation, mature forests) and the barred owl (lower elevation, riparian forests) should be explored to try to keep the two species apart. Further, some experts are questioning the classification of the barred owl as an “invasive” species in the Pacific Northwest based on genetic data of these western owls. After how many years of residence does a migrating species become “native?”.

A final proposal on the barred owl/spotted owl problem is expected this summer.

Woodlot in Columbus, Ohio. Photo by M., Wikimedia Commons

(Click on the following link to listen to an audio version of this blog …    Silent flight

When I was a graduate student at Ohio State in the late 1970’s, I took a course entitled ”Forest Biometry.” The course was mix of extremely useful topics for anyone who wanted to do field research in forested ecosystems, or who was working toward a position in which they would need to be able to make sense of field research reports. We covered simple, field mapping techniques (compass and pacing), the design of sample plots and sampling/cruising patterns, how to measure trees (heights and dbh’s)), and spent a lot of time on very practical statistics and data interpretation. It was a good course.

I was the only ecology student in the class. There were forest product majors, natural resource management majors, general agriculture majors and so on. There were 15 or 20 of us in the class, and we were divided up into working groups of four for our semester projects and reports. My group mates were taking the class as a degree requirement and were amazed that I was taking it as an open elective. There was a lot of math in this class, something most of my fellow students tried to avoid!

One of the things that the long history of Forest Biometry students had to do was map a two acre woodlot over on West Campus. I don’t know if this small piece of mixed hardwood forest still exits or not (Ohio State has done a lot of growing and changing in the past 40+ years), but even in the 1970’s these twoacres were, possibly the most measured and described bit of woods in the entire state of Ohio. Over the years, not only had the boundaries of the woodlot been mapped over and over and over, but, quite possibly, every tree in the woodlot had been identified, measured and located on map after map.

It was a very well-known space!

Great horned owl. Photo by C. Hume, Wiimedia Commons

One afternoon, I was out in the woodlot doing some tree measurements when I either saw something out of the corner of my eye or felt something move in close to me. I turned to my right and there, on a low branch of the red maple tree I was measuring, was a great horned owl!

The owl fixed both of his front-facing eyes on me and silently watched me for several minutes. He (based on his fairly moderate size, I assume that he was a “he”) then lifted up off of his branch and silently flew away. I never heard a whisper from  his incoming flight or from his departing flight. It was like he was in a soundproof bubble, moving about separately from everything else around him! This encounter was like a dream.

I have had other owl encounters that have emphasized the quietness in flight. The great horned owl up in my front yard spruce tree back at my home in Pennsylvania. The great horned owl settling down like a ghost out in the front yard here in Greeley when I was out last year looking at the lunar eclipse. Only owls fly with such stealth. Even little song birds raise a rattling ruckus when they lift off from the ground or a perch, and large birds pulse great waves of sound out from their liftoffs and landings.

Why and how are owls so silent?

Spotted owl with mouse. Photo by E. Brauar. Flickr

The why seems obvious. Owls must be quiet so that their prey doesn’t hear them coming! This is called the “mouse ear” hypothesis. It is very straightforward and very logical and probably not correct. There is a range of quietness that different owl species exhibit and those owl species on the noisier side of owl-normal don’t seem to have any difficulty catching prey. Certain owl species, though, are extremely quiet. If it’s not to conceal themselves from their prey, then why?

Great gray owl. Photo by USFWS, Public Domain

Another explanation of why owls fly so silently is called the ”owl’s ear” hypothesis. All owls rely on hearing to find prey but certain owl species preferentially utilize their sense of hearing to locate their food. These owls must be extremely quiet or else they couldn’t hear the tiny rustlings in the leaf litter or under the snow that mark the location of a potential meal!   Owls with broad facial discs (like great gray owls, boreal owls and barn owls) use this forward facing feature like a big, sound gathering disc. They pull in even very faint sounds and transfer them to their asymmetrically located “true” ears on the side of their heads. Their brains are wired to pinpoint the position of the sound source, and their strikes are aimed at those positions with amazing accuracy.

So the owls are silent especially so that they don’t mask the faint sounds of their prey!

How, then, can owls fly so quietly?

Noise comes from turbulence and friction. Air passing over a wing gets organized into turbulent flow which raises quite a racket. I remember a sharp-shinned hawk at a demonstration at the National Aviary in Pittsburgh being turned loose to fly over the heads of an audience. The clatter rough whirr of her wings flying a few inches over our heads were deafening! Lots of turbulence and lots of feathers- rubbing-on-feathers friction.

Owl wings. Photo by T. Higett. Wikimedia Commons

Owls lessen turbulence via two adaptations: 1. The front edge of their wing  has an extending  row of fine bristles (called “the comb”) that claw into the air rising over the wing and break it up into smaller and smaller volumes. This dispersion breaks up the turbulence of the air and dramatically reduces noise. 2. On the back edge of the wing there is a line of ragged feather edges that break up the air flowing over the wing and prevent it from gathering into a turbulent mass.

So the wing design of an owl keeps air from forming large, noisy, turbulent air masses.

Barn owl feather. Photo by K.C.Schneider. Flickr

Also the feathers of the owl are designed to minimize sound. The wing feathers have soft, elastic tips that dampen  noises. If you have petted an owl, something you should do carefully and only with permission, you know how soft and velvety their feathers are. Their feathers have a surface feature called a pennula. The pennula is a fine layer of fluffy fibers that separate each individual feather. Air flows through the pennula layer and the feathers pass over each other with a minimum of friction and a minimum of noise.

So some advance aerodynamics in wing construction and advanced material science in feather composition all work together to make the flight of an owl extremely quiet!

There is a new book by Jennifer Ackerman entitled What an Owl Knows. It is an impressive blend of science and colorful annecdotes about owls. Such wonderful and mysterious birds!  I recommend the book very highly!

Purple foxglove (Digitalis purpurea). Photo by Godot13. Wikimedia Commons.

(Click on the following link to listen to an audio version of this blog …. Chemicals from plants, dragons and more

Plants used to be an almost exclusive source of pharmacological chemicals for humans to treat or prevent illnesses or to resist the wide variety of biological pests and parasites that beset us. Pollen and plant samples from Paleolithic human habitation and burial sites suggest that herbal medicines were used by humans even tens of thousands of years ago.

Early recorded human history also richly describes a growing plant pharmacopeia. Five thousand year old Sumerian clay tablets describe the use of medicinal plants like opium and myrrh, and Egyptian papyri dating back nearly four thousand years list over 800 plant-derived medicines including ones based on cannabis, mandrake, castor beans and aloe.

Willow tree. Public Domain

Numerous medicines initially derived from plants are still available for human use (although many have been replaced by safer, more focused synthetic derivatives). Aspirin (“salicylic acid”) used to treat pain and inflammation and later recognized as an incredibly effective blood clotting preventative, was initially derived from the bark of the willow tree before its eventual synthetic synthesis by scientists at the Bayer Corporation in Germany. Digitalis derived from foxglove plants influences active transport pumps on the cell membranes of heart muscle cells and causes the heart muscle to contract more slowly but with more force (a great benefit in any number of conditions in which the heart is weakened). Quinine derived from the bark of the cinchona tree of Peru was used to prevent and treat the parasitic load in individuals with malaria (and also give a gin and tonic its snap!). Opium from the opium poppy has been the source of many important pain killing drugs and also the starting point from which the epidemic of addictive natural and synthetic opioids have been derived.

Twenty-one  years ago I wrote an essay entitled “Do We Need Nature.” In it I talked about one very important aspect of wild plants and animals: their incredible array of genes, proteins and other chemicals that might be able to be used to fight human disease. I called this of “tool box” of Nature. Recently I have come across several journal and news articles that have added to this “tool box” idea.

Mayapple (Podophyllum peltatum). Public Domain

In “Do We Need Nature?” I used the story of the Mayapple (Podophyllum peltatum) as an example of unexpected benefits from a wild species.  Mayapple dominates the spring understory vegetation of many of our damp. Eastern forests, and its abundance and commonness belies its rich history and ethnobotanical significance.

Native Americans recognized the chemical richness of the Mayapple. They used dilute preparations of its rhizome to treat a wide array of maladies (from constipation to liver and kidney disease). They also used a concentrated preparation of the rhizome as a poison. European settlers learned of the properties of Mayapple from the native peoples and similarly utilized these oral preparations.

In 1835 the drug “podophyllin”  was isolated from the Mayapple rhizome and by 1850 concentrated forms of podophyllin were available commercially. Podophyllin was used as a laxative, a “duct opener,” a de-worming treatment (it killed both nematodes and flatworms), and as promoter of bile synthesis and release. It also had many serious side effects and was quite toxic. A topical form of podophyllin was manufactured in 1942 and was found to be very effective in treating the genital warts caused by the human papillomavirus (HPV). HPV generated genital warts were at one time the most common sexually transmitted disease in the world, and untreated HPV infections can lead to cervical cancers. Podophyllin, then, the secondary chemical of the abundant and unassuming Mayapple, helped to play a role in the prevention of cervical cancer! More recently, the vaccine against HPV has assumed control of HPV infections, but podophyllin had a long history of effective treatment and use.

Jonathan Hartwell. Public Domain

Back in the April 1, 2017 issue of The Scientist, Jef Akst wrote about a scientist who helped to facilitate a large number of cancer therapy breakthroughs. Jonathan Hartwell joined the National Cancer Institute (NCI) in 1938 (and stayed there until his retirement in 1975). He set up a “natural products division” at NCI whose task was to explore natural plant chemicals for possible anti-cancer properties. Hartwell worked with fellow scientists in the Agriculture Department and at many major universities and over his 37 year career described over 3000 plant chemicals that had potential impacts on cancerous growths.  Hartwell published a book (Plants Against Cancer) in 1981 in which he summarized his research. This is a very difficult book to find in a print edition, but now, fortunately, it is available in an electronic form via Google Books. Hartwell was also the author of over one hundred scientific articles and books over his long career.

In addition to his laboratory work, Hartwell studied the herbal and medical lore of the ancient Chinese, Egyptians, Greeks and Romans for possible clues as to which plants to analyze. Any plant that was described to have efficacy against cancer in these pre-scientific cultures was carefully evaluated by Hartwell’s lab or by one of his university affiliates.

Chinese HappyTree (Camptotheca acuminada). Photo by Geography, Wikimedia Commons

Some notable successes from these research efforts were extracts from Chinese “happy tree” (Xi Shu tree, also known as Camptothica acuminate). Anti-cancer, chemotherapy drugs developed from this plant include camptothecin whose synthetic derivatives are still being used to treat metastatic colon and rectal cancers. Also extracts from the Pacific yew tree (Taxus brevifollia) led to isolation of the drug “taxol” which is used to treat breast, ovarian, lung, bladder, prostate and esophageal cancers along with melanoma.  Chemicals from the rosy periwinkle (Catharanthus roseus) led to the development of vinblastine which is used to treat both Hodgkin’s and non-Hodgkin’s lymphomas and vincristine which is used to treat both of these types of lymphomas and also childhood leukemia along with several other types of cancer.

The specific actions of these drugs in cells often involves disruption of the microtubules of the mitotic spindle or enzymes involved in DNA synthesis or repair. Thus, rapidly dividing cells (i.e. cancer cells) are particularly disrupted by these drugs (although even normal cells will be affected, too). As my oncologist once told me, chemotherapy drugs are poison, but they are poisons we try to control.

It has been estimated that 60% of the current chemotherapy drugs being used to treat cancers are either chemicals isolated from plants or derivatives of those plant chemicals.  We should all plant periwinkles (and Mayapples and Happy Trees!) in our gardens!

Komodo dragon (Varanus komodoensis). Photo by C.J.Sharp, Wikimedia Commons

Another part of the biological “tool box” are chemicals found in animals. An article in the New York Times (April 17, 2017) described a new type of antibiotic that was isolated from the blood of a Komodo dragon (Varanus komodoensis) by Monique Van Hoek and Barney Bishop of George Mason University. This antibiotic (named “DRGN-1”) killed both Gram negative and Gram positive bacteria and also dissolved their protective biofilms. It sped up wound healing in lab mice, too. The mouth of a Komodo dragon contains a rich, toxic microbiome of bacteria. When a dragon bites a large prey species (like a deer or a buffalo) it injects the bite wound with bacteria and also a recently described venom. The infection and the venom slowly disable the prey animal and the dragon, who has followed the bitten prey closely, eventually can feed on the stricken animal. Researchers assumed that for a dragon to house such a toxic oral microflora, it must have mechanisms to protect itself from both self-infection and also infections from the frequent bites from their fellow, often aggressively interacting dragons. Hence the discovery of DRGN-1! Researchers report that there are forty other substances in their dragon blood that may also have antibiotic properties!

The public health fight against antibiotic resistant bacteria may depend upon the blood of dragons (and other types of monitor lizards, crocodiles and even sharks!). There are more things in heaven and earth (and in our medicine cabinets!)  than we have ever dreamt of in our philosophies!

Male European eatwig. Photo by R. Hodnett, Wikimedia Commons

(Click on the following link to listen to an audio version of this blog … Earwigs

I have to admit, like most people, I have given earwigs very little thought. I mean their name “earwig” has led to some off-the-wall conflation with the mind-controlling, Ceti Eel that digs its way into Pavel Chekhov’s ear in the film “Star Trek 2: The Wrath of Khan.” I also had a rush of calls at my old Penn State office from people who, apparently, were seeing earwigs for the very first time and were extremely creeped out about them (this came the day after the television broadcast premier of the 1978 version of “Invasion of the Body Snatchers”). Maybe they were tiny pod-creatures dropping in from space?

I did write about earwigs in a blog many years ago (Signs of Summer 7, July 23, 2014). Let’s see if there is anything new about them!

The European earwig (Forficula auricularia), the most common type of earwig around, is a native insect species of Europe, Northern Africa and Western Asia that has been accidently introduced to North America, New Zealand, Australia and a number of other temperate and tropical countries around the world. Its first recorded appearance in the United States was in Seattle in 1907. It was likely brought to this country in a shipment of flowers, fruit, or vegetables, but given the earwig’s ability to find survival spaces in almost any type of biological or human-made materials, it might have arrived in almost any type of transported product.  In the hundred-plus years since it arrived in the United States, the European earwig has found its way to almost every region and every state in the country.

Female European earwig. Photo by LMBSanchez, Wikimedia Commons

There are twenty-two species of earwigs in the United States. Twelve of these species (like the European earwig) are alien exotics, and ten are endemic. Only four of these twenty-two species, though, are classified as pest (or potential pest) species.  Most of the earwig species in the United States actually are quite beneficial acting as shredders and comminutors in the soil decomposer community and as biological control agents (predators) for a variety of insect pests. The European earwig is classified as a pest species primarily because of its tendency to generate very large populations in places where people don’t want any insects at all (like under potted plants or on patios or porches). It is also acknowledged, however, that this species can also be an active predator of crop-damaging aphids, caterpillars, beetles, and midges. Its role as a pest controlling agent is especially important in organic orchards and farms.

The name “earwig” has a long and extremely non-scientific history. It is derived from the Old English word “earwicga” which translates as “ear wiggler.” There is an ancient myth that these very harmless (to humans, anyway) insects have the ability to crawl up the ear canal of a human and then eat their way into that unfortunate person’s brain (back to “Wrath of Khan?”). None of this is true, and it is very unclear why anyone would have thought that it was or why this myth would persist over many hundreds or thousands of years!

Female earwig with eggs. Photo by MHedia, Wikimedia Commons

The European earwig is a little over one half an inch long (females are larger than males). They have dark, red-brown bodies, reddish heads, yellowish legs, two long antennae, two membranous flight wings (which they seldom use) which they keep tucked under their hard, protective forewings, and two very distinctive cerci (“pinchers”) on the end of their abdomens. The shape of the cerci differ between males and females with females having straight cerci and males having curved cerci. These cerci are used to grab and secure prey and also, in males, as weapons in mating competitions.

European earwigs are nocturnal and spend the day in dark, moist places (like spaces under rocks, logs, surface vegetation, flower pots, leaf litter etc.). One frequently mentioned method of bio-control of earwigs is to make sure that your property is free of these potential daylight refuges. Earwigs are omnivorous and will consume plant materials (both living and dead), aphids, spiders, insects, insect eggs. They will also eat garden plants and a wide variety of fruit and vegetable crops but, very interestingly, only seem to do so when potential prey (like aphids) are not present in sufficient numbers. European earwigs also accumulate inside human habitations and can work their way into almost any open space or crevice. They can eat stored food products (flour, bread, cereal, crackers, etc.) and befoul clothes, books, laundry and more with their odiferous secretions.

European earwigs are solitary organisms and have no social behaviors or communication systems. Males and females meet up once a year, though, in order to mate. Males find females via pheromones that the females excrete in their feces. Males attracted to the pheromone then compete with each other for the attention of the female. It is thought that body size and especially cerci size are the critical variables in a male’s reproductive success. Mating takes place in early autumn.

Nesting female earwig with eggs and nymphs. Photo by Tom Oakes (2010), Wikimedia Commons

The mated female digs out a brood nest and lays her clutch of thirty to fifty eggs. This nest will also serve as the hibernation nest for the female and also for the male. The female will tend to the eggs stacking them up and then spreading them out making sure that fungi do not grow on them. She also will vigorously protect the eggs from possible predators. The eggs hatch in the spring and the first nymphs that emerge (the first “instar”) will remain in the nest and continue to be cared for by the female. The female guards and feeds the nymphs (via regurgitated plant materials) throughout the first instar stage (which is about the first month of life). This level of maternal involvement with offspring is very unusual in insects!

There are four nymphal stages in earwigs. In the second instar stage the female opens up the nest and the nymphs begin to go out at night to search for food. These second instars, though, tend to (or at least try to) return to the nest during the day. By the third instar stage, though, the nymphs have completely left the nest and move freely about the soil and litter habitat searching for food by night and seeking daylight refuges by day. These nymphs develop into adults in the late summer or early fall and then mating occurs and the cycle begins all over again.

European earwig. Photo by gbohne, Wikimedia Commons

Some female earwigs lay a second clutch of eggs after the second instar nymphs have left the nest. This second batch of eggs hatches and marches through the four nymphal stages very rapidly in the warm temperatures of summer and matures into adult earwigs at the same time as the overwintering clutch of eggs.

Earwigs are preyed upon by many species of birds (including chickadees and nuthatches) and are also eaten by a number of amphibians (especially toads). They are also parasitized by the parasitoid fly Bigonicheta spinopennis and susceptible to numerous bacterial and fungal infections.

So, here’s to earwigs! The best mothers in Insecta! Don’t worry about those brain-tunneling rumors!

Pecan orchard. Photo by H.F.Schwartz, CSU, Bugwood.org

(Click on the following link to listen to an audio version of this blog … Ecology of nut trees Part 2

Pecans are the sixth-most abundant dietary nut in the world. In 2022/2023, 0.164 million metric tons of pecans were sold on the world market. Pecans are primarily grown in the southern United States but with irrigation can be grown across the dry Southwestern states all the way west to California. There are also cold-hearty varieties that can be planted as far north as Oregon and Washington State. Georgia is the leading producer of pecans in the United States (142 million pounds a year) followed by New Mexico (77 million pounds per year).

A pecan tree reaches maturity at 12 years of age and may reliably produce nuts for 200 or 300 years! They generate very stable, long-term orchard ecosystems!

Pecans require about 68% of the water needed to support almond trees, and they need almost constant irrigation to survive and be productive. A pecan tree can only survive 2 or 3 weeks in drought conditions. High levels of nitrogen fertilizer are also needed to support nut production, and pest and disease control (weevils, aphids, a variety of fungal diseases) often necessitate the application of chemical pesticides and fungicides. Squirrels are also often a serious problem in pecan orchards. They are typically dealt with via guards and barriers attached to tree trunks and also by direct hunting and disposal.

The long, stable time frame of a pecan orchard is an extremely good feature of this system of nut production. The high water demand and the pesticide and fungicide uses, though, are significant environmental drawbacks.

Macadamis orchard. Photo by CABI Digital Library.

Macadamia nuts are the seventh-most abundant dietary nuts in the world. In 2022/2023, 78 thousand metric tons of macadamia nuts were sold on the world market. Macadamia trees are native to Australia and New Zealand but are grown in many countries around the world. Macadamias are the fastest growing nut crop in the world! Currently, South Africa is the leading producer of macadamia nuts (26 % TWP) with Australia in a close second place (22% TWP). China, though has been very actively planting 2 million macadamia trees a year and is expected to produce 63% of the world’s macadamia crop by 2025. The United States (primarily in Hawaii and more recently in California), Kenya, Guatemala,  Malawi and Zimbabwe also grow macadamia nuts.

Macadamia trees begin to make nuts after 5 years but do not reach maturity and full production potentials until they are 10 or 12 years old. Trees can remain extremely productive for over 100 years! The very stable, long-term macadamia orchards help to stabilize watersheds and reduce soil erosion. They also act to store considerable quantities of carbon (the average macadamia orchard is a net CO2 sink of 14.5 tons of C per year!).

Macadamia trees grow best when planted in regions that receive 50+ inches of rain a year. The trees, though, handle drought very well, but need water when going through a flowering cycle. Research has shown that they have a very precise level of control of their leaf stomata and, therefore, lose very little water through transpiration. Also, studies in South Africa have shown that minimal irrigation stimulates the trees to produce more higher quality and more abundant nuts.

The trees are subject to extensive insect and disease stresses, and are often grown using extensive pesticides and fungicides. Programs in South Africa, though, are working toward management schemes that minimize chemical intervention in the growing of these nuts.

Macadamia nuts are well on their way to becoming a truly sustainable crop!

Stone pine tree. Photo by Karova. Wikimedia Commons

Pine nuts are the eighth-most abundant dietary nut in the world. In 2022/2023, 41 thousand metric tons of pine nuts were sold on the world markets. Pine nuts are primarily harvested from wild pine forests. There are a few pine nut plantations, but their overall nut production makes up a very small percentage of the world’s pine nut crop. Historically, the harvesting of pine nuts involves gathering the ripe pine cones that have fallen from their trees. Large groups of laborers pick up the cones by hand and fill great bags of cones for processing. Some newer harvesting techniques used in China and Russia, though, actually cut cone-ladened branches from standing pine trees or even cut down the trees themselves to harvest cones still attached to their trees. These destructive harvesting methods can do great damage to the pine forest.

Most pine tree stands are not managed at all. There is no irrigation, no pesticide or herbicide use and no fertilizer applications. The only drawbacks to this system of pine nut harvesting are the possible excessive removal of a natural food source upon which a number of bird and mammal species depend, the destructive harvesting techniques employed by a small number of Chinese and Russian nut gatherers, and the extreme reliance on manual labor to gather the pine cones.

Pine nuts are harvested from a large number of pine species. In Northeast Asia the Korean pine (Pinus koraiensis) is the most frequently harvested, and in West Himalaya the chilgoza pine (P. gerardiana) generates most of the harvested nuts. In Europe, most pine nuts are gathered from stone pines (P. pinea) and in North America, most pine nuts come from the various pinyon pine species of the West and Southwest United States.

Pine nuts are very expensive because of remoteness of most of the pine forests and the costs of gathering and transporting the nuts. Overall, though, pine nuts are the most “natural” of all of the edible nuts and by far the most sustainable.

Brazil nut tree emerging from rainforest. Photo by MyFavoritePetSitter, Wikimedia Commons

Brazil nuts are ninth-most abundant dietary nut in the world. In 2022/2023, 28 thousand metric tons of Brazil nuts were sold on the world market. Brazil nuts are produced by a large, wild tree of the Amazon rainforest (Bertholletia excelsa). The Brazil nut tree can grow to heights of 160 feet and can live for 500 to even a 1000 years! It is one of the largest and longest lived trees of the rainforest! Almost all commercial Brazil nuts are harvested from wild trees. Attempts to grow Brazil nuts in plantations have not been successful.

Flowers of the Brazil nut tree are pollinated by an extensive array of wild bees. These bees are most abundant in the pristine rainforest, and, so, productive Brazil nut trees only grow in undisturbed rainforest ecosystems. Deforestation of the Amazon rainforest is having a very serious impact on Brazil nut production.

Agouti (several species of the rodent Dasyprocta) are larger, longer-legged relatives of guinea pigs that live in the Brazil nut tree rainforest. Agoutis are able to crack open the tough casing of the Brazil nuts and eat and also bury the Brazil nut seeds in food caches. Some of the cached seeds germinate and form new tree seedlings. This agouti-mediated seed burial is principal way that Brazil nut trees are regenerated in their ecosystems.

Brazil nuts in husk. Photo by L.Golgher, Wikimedia Commons

Brazil nuts are very high in selenium and if eaten to excess can cause a very serious selenosis syndrome. Symptoms of high blood selenium include bad breath, nausea, diarrhea, skin rashes and fatigue.

Brazil nuts are the epitome of a sustainable crop in their rainforest ecosystems. Their harvesting, though, is extremely labor intensive and may not conform to ethical labor standards. Also, all of the global stresses negatively impacting the rainforests of South America (deforestation, Climate Change, etc.) have negative impacts on potential Brazil nut production.

Peanut field in India. Photo by Abhay iari, Wikimedia Commons

Peanuts are by far the most abundant dietary nut in the world. In 2022/2023, 50.5 million metric tons of peanuts were sold on the world markets. This is a value that is almost 10X greater than all of the other dietary nuts combined! Peanuts are a below-ground nut crop that is only grown in extensively managed agroecosystems. Peanuts require less water than most other nuts (for example, peanuts use only 11% of the water required by almonds to produce an ounce of nuts). Peanuts have a very long growth and development period (4 to 5 months) and, so, can only be cultivated in places with long growing seasons.

Peanuts are legumes and, thus, have root nodules filled with nitrogen-fixing bacteria. This ability to biologically fix nitrogen reduces the overall requirements for fertilizer application.

Peanut plant. Photo by B.Ganguly. Wikimedia Commons

Peanuts flower above ground and after self-pollination, send the fertilized, budding ovary (a structure called a “peg”) down into the ground. The peanut then develops from this ovary. A single plant may repeatedly flower and send up to 50 pegs down into the soil. A typical peanut plant makes 35 to 50 peanuts.

The green parts of the peanut plant are typically left in the field after harvesting to form a “green manure” rich with nutrients for the growth of a subsequent crop.

Peanuts are beset by a wide array of pests and diseases and require high levels of fungicides, herbicides and pesticides to produce a viable crop. Peanuts and peanut products often contain high levels of these chemical residues. Organic varieties of peanut products sound like a very good idea!

To summarize: nuts are an important part of a healthy diet. They have both direct and an indirect effects on your health. Many nuts have serious environmental or ethical problems associated with their cultivation, harvesting or gathering. Brazil nuts, pine nuts, macadamia nuts and to a lesser degree, pecans and pistachios are good choices for edible nuts. Peanuts grown organically are also a good choice for a dietary nut. Almonds, walnuts and cashews have such serious problems that it is probably best to avoid them.

“Blossoming Almond Trees” by V. Van Gogh

(Click on the following link to listen to an audio version of this blog …. Ecology of nut trees Part 1

Looking at tree nuts (and peanuts) it’s important to recognize that growing these crops, like growing any crop, requires water and will generate pollution because of energy expenditures, fertilizer applications, and herbicide and pesticide use. From an ecological point of view, though, any way that water use and these various sources of pollution can be minimized will reduce the overall environmental cost of cultivation and push the production of these important food crops closer to a sustainable equilibrium.

Further, the harvesting and processing of nuts and seeds can be very labor intensive. There are many examples of severe exploitation of people working in these industries, and many of these exploitive practices are still ongoing.  We need to be sure that people are not being harmed by the processes involved in the gathering and preparing the nuts that we all want to eat.

Almond trees in bloom. Photo by Jausel, Wikimedia Commons

Almonds are the most abundant dietary tree nut in the world. In 2022/2023, 1.477 million metric tons of almonds were sold on the world markets. Almonds have extremely heavy water requirements, and they are being grown primarily in the dry valleys of central California. The water needed to grow these California almonds is delivered by irrigation systems fed by ground water, snow melt and the dwindling water of the Colorado River. For decades it has been repeated that it took one gallon of irrigation water to produce  single almond nut. This very steep water demand ratio has been disputed by a number of publications and websites supported by the almond industry, and a paper published a few years ago in the journal Ecological Indicators showed quite definitively that this one gallon for one almond nut was incorrect. It actually takes 3.2 gallons of irrigation water to make a single, California almond.

Harvesting and processing of almonds are accomplished mechanically (tree shakers, front loaders, etc.) so there is little exploitive labor involved. Growing almonds, though, involves high levels of pesticides. More pesticides are used on almond trees than on any other crop grown in California! The impact of these pesticides on pollinating organisms like bees has been so severe that almond growers are required to bring in thousands of honey bee hives every year in order to accomplish the pollination of their trees (see Signs of Fall 7, October 18, 2018).

The almond industry in California is very profitable, but its existence is dependent on the unsustainable use of obscene amounts of increasingly diminishing water and also upon ecosystem-destroying levels of pesticides. Do not eat almonds!

A walnut orchard close to the Sacramento River in Butte County, California. Photo by F. Schulenberg. Wikimedia Commons

Walnuts are the second-most abundant dietary nut in the world. In 2022/2023, 1.156 million metric tons of walnuts were sold on the world markets. Growing walnuts requires only half of the amount of water as growing almonds. Most walnuts are grown in China. Some of the Chinese walnut groves are located in dry, continental climate zones and, therefore, need extensive irrigation. Others are located in subtropical and northern, warm temperate climate zones and, therefore, rely primarily on rain for their water sources. Some Chinese walnuts are also harvested from wild, forest trees. The walnuts grown in the United States, though, are primarily grown in managed orchards in California’s Central Valley and are therefore extensively irrigated.

A walnut tree will begin to make nuts after 5 to 7 years and is likely to become commercially productive after 10 years. Productivity is not constant, though, and typically a walnut tree will have 2 or 3 years of high nut production every 5 years. Productivity begins to decline after 35 years, so trees are usually cut down at this age.

Walnut trees are wind pollinated and are able to self-fertilize. This greatly simplifies the management of the nut cycle.

Walnuts are beset by a wide range of fungal, bacterial, viral and insect pests. Most require significant chemical pest management in order to produce an acceptable crop of nuts. Walnut trees also produce the toxin juglone in their roots, buds and nut hulls. Juglone accumulates in the soil under a walnut tree and can inhibit the growth of most other plants even many decades after the walnut tree is gone.

Walnuts have many environmental negative qualities but they are less of an environmental disaster than almonds.

Cashew tree. Photo by MJE Hermann. Wikimedia Commons

Cashews are the third-most abundant dietary nut in the world. In 2022/2023, 1.095 million metric tons of cashews were sold on the world market. Cashews require large amounts of water in order to grow. Their water demands, in fact, are quite similar to those of almond trees. Cashews can only grow in tropical climates and in the continental United States will only grow in southern Florida. Cashews are native to Brazil but were transported and planted extensively throughout tropical Africa and Asia following the opening of the Americas in the late Fifteenth Century. Currently, the major producers of cashews are Ivory Coast and India. Some cashew plantations utilize irrigation in order to optimize water delivery during periods of maximum water need during the nut production cycle, but a large number of these cashew plantations simply rely on rainfall to provide the necessary water.

A cashew is actually a seed that develops inside of a fleshy fruit called a cashew apple. The harvesting and processing of these cashew seeds is labor intensive and has historically been carried out by women in India for very little pay and at some risk to their health and wellbeing.

So cashews, especially cashews grown in non-irrigated plantations, are relatively sustainable and generate few environmental problems. The history of exploitative labor practices in the cashew industry, though, requires that the health and safety of the cashew workers be guaranteed by some type of fair trade organization certification.

Pistachio orchard. Photo by PAC55. Wikimedia Commons

Pistachios are the fourth-most abundant dietary nut in the world. In 2022/2023, 0.747 million metric tons of pistachios were sold on the world market.  Pistachios are water-intensive nuts and require 71% of the water needed to grow almonds. Since half of the world’s production of pistachios occurs in the Central Valley of California, the water used to grow these nuts primarily is delivered via irrigation. Pistachios are grown, though, with fewer pesticides than almonds or walnuts and, therefore, are less damaging to the environment.

Pistachio trees take seven to ten years to reach a productive size but can live and be productive for 100 to  300 years! A pistachio orchard, then, unlike the transient orchard systems of almonds and walnuts, is a relatively stable, long-lived ecosystem.  Most orchard-grown pistachio trees, though, are only allowed to live 50 to 80 years (which is still about 3 to 4 times longer than cultivated almond trees and twice as long as cultivated walnut trees).  Trees older than 80 years are too massive to be effectively shaken by the mechanical tree nut harvesters.

Pistachio trees have distinct genders, and in a pistachio orchard, typically eight female (nut-bearing) trees will be planted for each male (pollen-producing) tree. The pistachios, like walnut trees, are wind pollinated so there is no need for insect or other types of pollinators. This is a major advantage over the bee-dependent pollination of almonds.

So, pistachios do require a lot of water, but other features of their cultivation make them a much better environmental choice than either almonds or walnuts.

Hazelnut orchard. n.macneil. Wikimedia Commons

Hazelnuts are the fifth-most abundant dietary nut in the world. In 2022/2023, 0.685 million metric tons of hazelnuts were sold on the world market. Hazelnut trees require only 65% of the water needed to grow almond trees. Hazelnut orchards can be managed, then, with very little to no irrigation. Hazelnut orchards in Oregon have historically not required irrigation water, but with the elevated temperatures and disrupted rainfall patterns attributed to Climate Change, increasingly irrigation is needed to maintain these orchards.

In Turkey (where 70% of the world’s hazelnuts are grown), most hazelnut production occurs in four northern provinces along the coast of the Black Sea. The climate on this coast is wet and mild and the hazelnut trees are sustained primarily by water from rainfall. A major environmental concern from these plantations is inorganic fertilizer application and its runoff into surface water. Attempts are being made in Turkey to develop an “organic” hazelnut industry that avoids these potential pollutants.

Also in the Turkish hazelnut orchards there are a number of insect pests that can have significant impact on the nut crops. Pesticides are used to mitigate the impact of these pest species. One species that has recently invaded the Turkish hazelnut orchards is the brown marmorated stink bug (Halyomorpha halys). This East Asian insect pest, you may remember, also recently invaded North America and has caused extensive damage to many agricultural systems (see Signs of Fall 7, September 26, 2013, Signs of Fall 7, October 8, 2015, and Signs of Summer 3, June 16, 2016).

Hazelnuts, then, seem to be one of the more environmentally friendly dietary nuts.

(Next week: pecans, macadamia nuts, pine nuts, Brazil nuts and peanuts!)