Signs of Spring 11: Predators

Photo by Mythicmeadows, Wikimedia Commons

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The interaction of large carnivores with small and medium sized carnivores was explored in a wildlife population study conducted by Penn State University researchers (Penn State News, August 8, 2018). When a large predator (like a cougar or a wolf) is removed from an ecosystem (an occurrence that has been observed in most human-occupied habitats) there are a number of expected and unexpected consequences.

Expected consequences include the unregulated growth of primary prey populations that the large carnivore preyed upon. Here in Western Pennsylvania the exponential growth of white-tailed deer populations in our wolf-less and cougar-less biotic communities is an excellent example.

Less anticipated consequences of the loss of a large predator, but still quite logical, are the increases in numbers of small to medium-sized predators (like foxes, bobcats and coyotes) whose numbers had been kept in check by the direct or indirect actions of the larger carnivore. The unexpected consequences of these increases in these predators is the increasingly intense competition between them and possibly outright predation of the larger species on the smaller. Coyotes, for example, are extremely intolerant of red foxes and will kill any red fox that they come across. Shift of the predator profile away from the small predators to the medium sized predators can lead to explosive, uncontrolled growth of the small predator’s small prey species. Lack of red foxes, for example, could lead to large increases in mice populations which could, in turn, negatively affect an ecosystem’s plant community and possibly contribute to increases in diseases and parasites carried by the mice. Possibly the explosive growth of white-footed mice here in Western Pennsylvania (and the associated rise in black-legged ticks and Lyme Disease transmission) is a consequence of declining red fox numbers due to the local increases in eastern coyotes.

Golden jackal. Photo by C.J.Sharp, Wikimedia Commons

Similar observations on these consequences of large predator removal are being made in Europe. Wolves were effectively extirpated from the European continent by intensive hunting and poisoning campaigns. The removal of this large predator has allowed the golden jackal (Canus aureus)  a nearby, medium-sized predator to spread across Europe (see New York Times, January 11, 2019).

The golden jackal, a native of the Middle East and countries all across southern Asia, is a 15 to 30 pound canid (slightly smaller than a coyote) with omnivorous feeding behaviors that range from active carnivory to detrital and carcass scavenging. Golden jackals were first reported in Europe back in the 1800’s but have, since the middle of the 20th Century become very widespread. In the first two decades of the 21st Century, their numbers and extent of distribution have increased explosively.

Golden jackals are well adapted to not being seen. They live in small family groups typically of four to six individuals with one breeding pair, they tend to hunt alone, they are very furtive and they are nocturnal. They do have a tendency to howl, though, and this howling can be stimulated by other jackals or by other sources of noise (like church bells, for example). Golden jackals especially favor lowland habitats ideally near water (like a river, lake, canal, or the seashore). They also tolerate dry habitats, though, almost up to an extreme desert. They are not well adapted to snow, however, and must travel in the tracks of other animals when moving across a snow covered landscape. For this reason, many ecologists feel that the reduced snow fall and warmer temperatures in a climate changed world will favor the further proliferation and expansion of golden jackal populations.

Wolves attacking moose on Isle Royale. Photo by R. Peterson, Wikimedia Commons

And, finally, looking at some predators closer to home, it was reported in Science this past fall (Sept. 21, 2018) that the wolves of Isle Royale are going to be “rebooted” (their term, not mine!).

Isle Royale is a 206 square mile island in the northwestern corner of Lake Superior. Technically, the island is part of the state of Michigan, but functionally the main island and the hundreds of smaller islands around it make up Isle Royale National Park. Isle Royale is a patchwork of complex habitats and is the home for populations of moose and gray wolves that were each introduced to the island back in the early years of the 20th Century.

For the past 60 years the Isle Royale moose and wolves have been closely studied. The simplicity of their predator/prey dynamic and the isolated nature of their island habitat have enabled researchers to very precisely observe the population interactions and their ebbs and flows.

The ideal wolf to moose population ratio for an island the size of Isle Royale was calculated to be 25 wolves to 1500 moose. Over the six decades of study, though, this ratio was never achieved and population stability was never observed. Moose numbers fluctuated wildly from a low of 540 individuals to a high of 2450 individuals. Wolf numbers also careened up and down from an historic low of 14 wolves to a maximum of 50 wolves. This summer, though, there were only two wolves left on Isle Royale: an aging mated pair of closely related individuals (the female was the daughter and the half sister of the male). Although over the years new wolves have arrived on Isle Royale (either after a long, cold swim or an icy trot across the winter lake ice!), the wolf population on the island had succumbed to the insidious effects of severe inbreeding.

Photo by USDA Forest Service, Public Domain

The consequences of this decline in the wolves has been very predictable. The moose population has grown extensively, and grazing by this large number of moose throughout the park has caused a decline in habitat quality of the island. The island is not in  sustainable state!

After a long debate, the National Park Service has decided to “reboot” Isle Royale’s wolf population by introducing new wolves to the island. Some of these wolves will come from Michigan and others will come from Ontario, Canada. The 20 to 30 wolves that will be added to the park will have, then, a broad and diverse gene pool which will, hopefully, avoid the inbreeding problems.

None of these added wolves, though, will have had any experience hunting moose! It is expected, though, that they will quickly acquire moose hunting skills in this very prey limited ecosystem. As one researcher put it, “wolves are wonderful observational learners, and hunger is a strong motivator to test any potential prey.”

I will keep you posted!

 

 

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Signs of Spring 10: Bees and Herbicides and Pesticides, Bats and Viruses

Photo by Aqua Mechanical, Flickr

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Glyphosate is the active ingredient in the herbicide Roundup, and, not surprisingly, it is the most widely used herbicide in the world. Glyphosate functions by inhibiting the activity of a set of plant enzymes that control the synthesis of aromatic amino acids (tyrosine, tryptophan and phenylalanine). This disrupted amino acid metabolism, then, results in defective protein synthesis and ultimately causes the death of the plant. Since these glyphosate-affected enzymes are not found in animals, glyphosate, at concentrations used in herbicide applications, is alleged to have little effect on animals and is advertised as “safe” weed and grass killer. Many bacteria, though, have the enzymes that are affected by glyphosate and there is some concern that both soil bacteria and also microbiome bacteria could be affected by glyphosate applications.

Honeybee gut microbiomes have long evolutionary histories and have been strongly conserved over millions of years (see Signs of Summer 11, July 27, 2017). These gut microbiome bacteria are important as barriers against infection by pathogens and also in the chemical conversion of raw nectar into honey.

Honeybee. Photo by C.J.Sharp, Wikimedia Commons

In a paper published this past fall in the Proceedings of the National Academy of Science (September 24, 2018) a research group from the University of Texas showed that glyphosate exposure greatly reduces levels of a common gut microbiome bacterium in honeybees and causes those affected bees to be more susceptible to infections by pathogenic bacteria. These impacts may also affect the nourishment and energy levels of the bees and may even play a previously unrecognized role in the development of Colony Collapse Disorder.

These researchers also point out that glyphosate may impact the gut microbiome bacteria in many animal species. Studies looking at the impacts of glyphosate on humans, for example, should include along with possible cancer connections and neurodegenerative disorders, possible disruptions of the human microbiome.

In another paper published in Science last fall (November 8, 2018) researchers at Harvard University examined the impact of pesticide exposure on the behavior of bumblebees inside their nests. Using high performance cameras and coded markings attached to the backs of all of the individual bumblebees, the specific locations, interactions, and other behaviors of the nest bumblebees were recorded over a two week period of time. Twelve nests were set up in the laboratory with half of the nests having access to nectar sources that contained the widely used neonicotinoid pesticide imidacloprid. The other six nests were given access to nectar that did not contain imidacloprid.

Bumblebee queen. Photo by M. Cooper, Wikipedia Commons

The bumblebees that were exposed to imidacloprid were less active in the nest compared to controls and did not participate in nest maintenance or larvae care. Exposed bumblebees also had fewer social interactions with their fellow nest inhabitants. These altered behaviors were particularly noticeable at night while, interestingly, during the day especially as the experiment went on, pesticide exposed bumblebees actually behaved in increasingly normal ways.

Pesticide exposed bumblebees, though, were less able than controls to regulate the temperature of their nest. None of the bumblebees in imidacloprid exposed nests constructed the expected thermal insulating, waxy barriers that function to prevent cold temperatures from damaging developing larvae. Larval care and development, then, were significantly affected by the pesticide.

Exposure to imidacloprid has been previously show to reduce foraging activity in bumblebees with the consequential reduction in nectar and pollen gathering and the decline in the overall health and vigor of the nest. This impact has led the European Union to ban imidacloprid use in EU countries (see Signs of Summer 4, June 26, 2018).

Mexican free-tail bats. Photo by A. Froschauer, USFWS.

Bats have many very positive ecological roles. They are vital pollinators and seed dispersing agents, and they consume a vast number of potentially disease carrying and crop destroying insects (see Signs of Summer 1, June 7, 2013).

Bats also, though, have a few less positive ecological features. For example, they carry and disseminate, sometimes across vast distances, some of the most deadly viruses known to humans including Ebola, Marburg and the SARS corona virus. Bats carrying these deadly pathogens, though, never seem to be ill. Somehow they act as reservoirs for these viruses but never become victims. Virologists at China’s Wuhan Institute of Virology explored this resistance of bats to viral illnesses and published their results in Science.

Previous ideas about viral resistance in bats centered on two hypotheses: 1. Possibly a bat’s immune system can make large numbers of “naïve” antibodies (i.e. antibodies that did not yet have specific antigen recognition sites). These circulating, naive antibodies could then mediate the very rapid immune system destruction of encountered viruses. Or, 2. The high body temperatures seen in bats during flight might stimulate immune activity much like the body temperature elevations seen in fever. Unlike fever, though, this acceleration of immune activity could easily be stopped by simply landing and ceasing flight muscle contractions.

The virologists at Wuhan examined the fundamental genetic sequences of two very distantly related bat species and found a core of highly conserved (and, therefore, very important!) genes that act to regulate the bats’ immune systems. Central to the protein products of these genes was a regulator protein that is found in all vertebrate immune systems. This protein is called STING (“STimulator of INterferon Genes”).

STING detects strands of DNA and RNA that are in inappropriate cellular locations and then triggers an immune cascade that destroys them. Often these DNA’s and RNA’s are viral nucleic acids, but they can also be fragments from a cell’s own genome that may have broken loose due to metabolic disruption or stress.

Indiana bat. USFWS.

The bat version of STING triggers a much more subdued metabolic response than the STING from other vertebrates. Many pathogenic viruses, in fact, damage or even kill their hosts because of the uncontrolled immune cascades and inflammatory storms triggered by their STING proteins! Bats, possibly, can carry their wide array of pathogenic viruses because of their very mild STING response!

But why do bats have such a toned down STING response? Bats are the only flying mammal, and , apparently, the metabolic stress of flight especially through the generation of high levels of free radicals from very active mitochondria in their flight muscle cells, leads to repeated breakage of their cellular DNA with the subsequent leakage of the nucleic acid fragments out from their cellular nuclei. Bats, then, have evolved a muted STING response to enable them to tolerate these metabolic stresses of flight, and the unintended consequence of this adaptation is their ability to carry so many types of viruses in their bodies.

There may be another unintended consequence of these muted STING proteins and their extremely down-regulated inflammatory responses. Reduced inflammation may be one of the causes of the very long life spans seen in bats. Bats do live much longer than any other (non-flying) mammal of similar size.

 

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Signs of Spring 9: Sycamore Trees

Photo by Dwspig2, Wikimedia Commons

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The Ohio State University campus is a beautiful place to walk and wander, and I did a lot of each back when I did my Master’s degree there. One place on campus that I loved to go was south of the Oval down in a shady hollow near a pair of old and venerable sycamore trees. The trees had short, thick trunks that were five or six feet in diameter at chest height. The trunks branched four or five feet up into thick sets of spreading branches.  There was a bench nearby where on nice days in the spring and summer I would eat my bagged lunch and read something that was not related to ecology or soil science. I imprinted on these sycamores and felt very at home in their presence.

I found our recently that these trees went through an existential crisis back in 2010! They were marked to be cut down in order to build a temporary construction road for the expansion of the nearby medical center. Fortunately, I was not the only person who valued these trees! A group of Ohio State employees gathered 1500 signatures on a petition to save them, and the president of the university eventually agreed to revise the building plans. This crisis and petition led to the formation of OSU Campus Tree Inventory and the eventual certification of the campus as one of the  Arbor Day Foundation’s “Tree Campus USA” sites.

A lot of good, then, came from this very near destruction of these two hundred year old trees!

Pinchot Sycamore, Simsbury, CT. Photo by Msact, Wikimedia Commons

Sycamores are primarily trees of the forest rather than the city. You see sycamores alongside streams and creeks or on the slopes of ridges where seeps and springs make the ground wet for a good part of the year. In fact, European settlers looked for the distinct colors of the sycamore’s bark in order to locate springs from which they could draw potable water.

In the uncut North American forest sycamores lived for 700 or 800 years and attained great girths if not particularly spectacular heights. Many of these trees had trunks that were  14 or 15 feet in diameter. George Washington described a pair of sycamores in his diary when he was in the Ohio Valley in 1770. One was just shy of 45 feet in circumference (just over 14 feet in diameter)  and the other was just over 31 feet in circumference (about 10 feet in diameter).

Currently, the largest sycamore in the Eastern United States is growing in Ashland, Ohio. It is 129 feet tall with a 15 foot diameter and a 48 ½ foot circumference. It is a true giant even compared to the sycamores described by the early explorers of North America!

Photo by T. Mues, Flickr

A very interesting aspect of these old sycamores is that they tend to rot out their heartwood while maintaining a strong, outer, living wood shell. This forms cave-like hollows at the ground level and chimney-like cylinders up in the crowns. Many European settlers took advantage of these “sycamore caves” and lived in them sometimes for several years until they had amassed sufficient resources to build a cabin. There is a delightful essay about the American sycamore and early North American settlement in Luke Bauserman’s “The Weekly Holler” (January 15, 2017).

Many birds used the upper hollows of the sycamore trunks as sheltered locations for their night roosts and nests. In fact, it is likely that these sycamore “chimneys” were the prime nesting and roosting habitat for the chimney swift prior to the European colonization of North America. The European settlers brought  many things to North America and took away many others, but their chimneys were of great importance to the vertically roosting and nesting swifts especially after the large hollow trees of the “settled” forests were cut down to make way for a more agriculturally oriented existence.

London plane trees in Wadsworth Park. Photo by P. Halling. Geograph

The wild American sycamore has a human created (or at least human facilitated), urban doppelganger called the London planetree. The creation of this hybrid is somewhat shrouded in mystery and many silvics books and websites offer only vague hypotheses about when and where exactly the London planetree came into existence. There are a few forestry historians, though, who have pulled together some very logical ideas about the origin of this “other” sycamore.

The trade in exotic plants from North America began almost immediately upon the discovery and initial exploration of the continent. Avid gardeners in England and throughout Europe imported and planted North American plant species (including the American sycamore) side by side with native plant species and also many other exotic species from around the world.

Ben Venables in his 2015 essay on the London planetree in the web magazine The Londonist contends that John Tredescant planted both the American sycamore and the Oriental planetree in Vauxhall Garden in Kensington (London) in the early part of the 17th Century. These trees, then, by the mid-1600’s had cross-pollinated and self-hybridized to create the London planetree.

Van Gogh’s “Road Meanders at St. Remy.” Public Domain

The vigor and heartiness of the hybrid was quickly recognized. Its ability to grow and flourish in the soil and space-stressed confines of the city, and its ability to tolerate the often toxic air pollution of an urban environment made it an ideal choice for street-side and urban park planting. Over half of the city trees in London are London planetrees and many European cities (including Paris, Prague and Vienna) have extensive stands of London planes along their beautiful boulevards. Smaller cities also planted London planetrees as is reflected in a famous painting by Vincent Van Gogh entitled “The Road Meanders at Saint-Remy” (1889), a painting that is sometimes referred to as “The Large Plane Trees.”

Historical photo of Apollo Iron and Steelworks housing, Vandergrift, PA, Public Domain

Here in Western Pennsylvania many towns have London planetrees. Nearby Vandergrift, PA (a town designed by Frederick Law Olmsted) has a beautiful set along its curving streets. There are also some large London planetrees along Pittsburgh’s Allegheny River Boulevard. These trees lean out and over the roadway in a very disconcerting manner as they grow toward the limited sunlight  in the shady valley of the Allegheny River.

 

Sycamore on Rock Furnace Trail. Photo by D. Sillman

There are few simple ways to tell American sycamores and London planetrees apart. The most obvious, to me, is their bark. Both have patchy, peeling bark of white, brown, green and gray that easily distinguishes these trees from all of the other types of trees around them. The London planetree, though, has this type of bark all the way from ground level to high up into its branches. The American sycamore, on the other hand, has dark brown, deeply furrowed bark on its lower trunk and only displays the “sycamore bark” on its upper trunk and branches. Their leaves are different, too. American sycamores have large leaves that have a vague maple-tree appearance to them. They are broadly ovate with 3 or 5 shallow lobes and wavy edges with scattered teeth. The London planetree also has large leaves, but they are more deeply divided into 3 to 5 lobes with smooth edges and few teeth. The fruits of these trees are similar in appearance (brown, somewhat fuzzy balls that stay on the tree through most of the winter), but the American sycamore usually has single balls hanging from its branches while in the London planetree the balls are usually in pairs.

A number of tree guides stress that location is also a good way to tell the American sycamore from the London planetree. A sycamore-like tree growing in a city or town is likely to be a London planetree while one growing along a hiking trail or in the woods is likely to be an American sycamore.

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Signs of Spring 8: Nests

Bluebird nest. Photo by cbgrfx123, Flickr

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Over the past five years Deborah and I have gotten very familiar with many types of birds’ nests. Working with the Cavity Nesting Team at Harrison Hills Park we have found and described a variety of grass and twig spun nests, cup nests, moss nests and random stick pile nests inside of our nesting boxes and have been able to work out the identities of the birds who have constructed them.

Tree swallow nests. Photo by T. Schweitzer, Flickr

Bluebirds, for example, use fine grasses when they weave their tall, cup nests, while tree swallows tend to use coarser grasses and almost always include a large number of feathers (either their own or feathers from other bird) in their nests. Chickadees build their nests with a predominance of mosses, while house wrens simply fill the nesting box with a seemingly chaotic array of small sticks that, somehow, has enough room for eggs, nestlings and the incubating adult. House sparrows make relatively shapeless nests in part out of natural materials with a large amount of added, human-made trash (candy wrappers, string, ribbon and even cigarette butts (I’ll come back to a further discussion of cigarette butts in a nest later)).

Chickadee nest. Mrgfan, Wikimedia Commons

We started our Cavity Nesting Project in 2015, and none of us on the team had a great deal of familiarity with birds’ nests. Also, we were initially uncertain about whether we should leave previously used nests in the boxes through the season or remove them when their individual nesting cycle was completed. Several scientific studies had found that the presence of old nests actually encouraged subsequent nest formation in natural nest cavities and nesting boxes. Other papers, though, stressed that old nest removal was important to help control the proliferation of nest parasites.

After our first, early spring round of bluebird nesting in 2015 we did remove several of the nests and put them in sealed plastic bags so that we could take them away from the nesting sites (we did not want to attract nest predators) and then dispose of them. One bag, though, ended up on top of the garbage can in my garage rather than in the trash itself. After three or four days I heard a buzzing noise in the garage and found that the bag was now full of trapped, adult blowflies.

This inadvertent experiment indicated to us that blowflies were present in our nesting areas. Blowflies can be significant nest parasites and can cause not only debilitation but even death of nestlings. From then on we removed all old nesting materials and disposed of them in sealed plastic bags. The positive impacts of reducing these parasites, we assumed, more than offset the loss of the possible stimulus that the old nests could impart to the nesting birds.

Nests are, of course, the place where birds lay and incubate their eggs and nurture their nestlings. Many bird species make iconic, woven, cup-shaped nests. Many other bird species, though, make very different sorts of nests.

KIlldeer nest. R. Cameron, Flickr

Killdeer, for example, put almost no work at all into the construction of their nests. They may push a few stones or some sticks or vegetation around to make a small clear spot (called a “scrape”) in which they lay their eggs. The eggs are well camouflaged by their colors and patterns and are remarkably hidden even when out in the open. Many years ago Deborah and I and our children rented a summer cottage on Chincoteague Island and were noisily greeted by a female killdeer every time we stepped out of our front door. We knew that the female was protecting a nest somewhere in the front yard (a weedy, sand and pebble habitat that was maybe 1600 feet square). Over the week we were on the island, we searched carefully through the weed cover of the yard but never did find the nest.

Killdeer also make scrape nests up on the gravel roofs of the buildings. At Penn State New Kensington it is a loud Sign of Spring and Summer to be dive bombed by some of these roof nesters whenever you go out or in the doors of the Engineering Building!

There are other birds who make even less of a nest than the killdeer. Cliff nesting murres and guillemots simply lay their eggs on bare rock ledges. They rely on the shape of their eggs (pointy at one end and rounded on the other) to make sure that any rolling of the egg will simply take it in a circle (and not straight off the edge of the cliff).

Birds like cowbirds and old world cuckoos don’t make nests at all but instead deposit their eggs in the nests of other bird species. Cowbirds originally were birds of the prairies that followed the great herds of bison. They fed on the insects that were attracted to the animal herds or stirred up by their activity. The unpredictable timing of the herd movements did not allow the cowbirds sufficient weeks to nest and raise their young. Using the nests of other birds and letting those birds rear their young was a logical evolutionary solution to their nesting crisis. The alteration of the North American forests by European settlement, though, opened ecological corridors for the prairie cowbirds and allowed them to move out into a wide variety of habitats. Today cowbirds are found all across North America and are responsible for a significant proportion of the declining populations of many native song birds.

Short-eared owls hunting storm petrals on Genovesa Island

A few birds make nests in underground burrows. Storm petrels, for example, on the Galapagos Island of Genovesa make their nests down in the volcanic rock tunnels and are hunted both inside the tunnels and at their surface entrances by diurnally active short-eared owls. The lava tunnels provide the only protective cover on this rocky, treeless island and the petrels (and their predators!) have quickly adapted to using them.

Birds’ nests range in size from delicate, spider webbing and thistle, bottle-cap-sized nests of hummingbirds to great platforms of thousands of pounds of sticks piled high up in trees by bald headed eagles. Some nests are meant to be used just once, while other nests may serve a number of generations of nestlings.

What plant materials a bird uses to build its nest also has an impact on the health and success of the nestlings. In a paper published this past summer (Proceedings of the Royal Society B, June 6, 2018), researchers at the Max Planck Institute for Ornithology found that starlings reared in nests to which aromatic herbs (including hogweed, cow parsley and goutweed) have been added by the parents (or by the researchers) had higher red blood cell counts, more robust immune system functions and fewer bacteria than starlings reared in non-herb infused nests. Further, the parental starlings incubated the eggs and nestlings longer in nests that had the added herbs suggesting that the added herbs acted as a tranquilizer for the parent causing it to linger longer on the nest.

Nest made with human trash. K. Stuedel, Flickr

Also, a study published in the Journal of Avian Biology (June 20, 2017) looked at house finch nests in Mexico City. These Mexican house finches, like the house sparrows I mentioned previously in Harrison Hills Park here in Western Pennsylvania, add cigarette butts to their nests. These cigarette butts add nicotine (a powerful, “natural” pesticide) and other chemicals to the nests that reduce the numbers of nestling parasites (like ticks). Further, the study suggests that parental house finches may actually add cigarette butts in direct proportion to their perception of the parasite load in the nest!

So, it’s spring and there are nests everywhere doing the job in some obvious and some subtle ways to help rear the next generation of birds!

 

 

 

 

 

 

 

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Signs of Spring 7: The Cicadas Are Coming!

Photo by K. Schulz Flickr

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Every seventeen years the quiet parks and forests of Western Pennsylvania explode with sound. Over a four or five week period in May and June periodical cicadas (also called “seventeen year locusts”) emerge from their underground nurseries in densities of tens of thousands to several millions of individuals per acre and begin to generate a roar that blocks out not only most of the other sounds of nature but also the usual crushing din of human existence!

Pay attention, everyone! 2019 is a Cicada Year!

It is the male cicadas that are making all of the noise. Their sound producing organs are on the undersides of their rounded abdomens, and their buzzing is intended to attract female cicadas so that they can reproduce. The male cicadas’ bodies are hollow and act as resonance chambers to amplify the buzzing which can be as loud as ninety decibels (the equivalent of the roar of a nearby power mower or a small chain saw). The ability to generate noise of this magnitude has earned the periodical cicada the title of the “world’s loudest insect.”

There are over 1500 described species of cicadas in the world, but only seven are classified as “periodical.” The life cycle of a normal, “annual” cicada (like our yearly “dog-day” cicadas, for example (see Signs of Fall 1, September 6, 2014)) can span several years and typically includes an extensive larval stage in which the cicada lives underground feeding on the fluids of tree and other plant roots. In periodical cicadas this underground portion of the life cycle is stretched out to intervals of thirteen to seventeen years! These adult “magical” cicadas (their genus name is Magicicada!), then, spend their allotted month in the open air buzzing and reproducing after more than a decade and a half of dark, subterranean existence!

Photo by M. O’Donnell Flickr

Adult periodical cicadas have stout, black to brown bodies that are just over one inch long.  They have two pair of membranous wings that are tipped in orange. The front wings are twice as long as the hind wings and have an open span of about three inches. The head is dominated by a pair of large, bulging, red eyes. They are slow flyers and are easily taken by a wide range of predators.

There are seven species of periodical cicadas all of which are found exclusively in the eastern United States from the Great Lakes down to the Gulf of Mexico. The three species in the northern portion of this range tend to have seventeen year life cycles while the four species in the southern portion tend to have thirteen year cycles. There is considerable overlap in the ranges of these different types but little potential for interbreeding because of the asynchrony of the emergence of their adult forms.

In both the northern and southern ranges the cicada species form communities that have synchronously timed emergences. These cicada communities are called “broods.” These Cicada Broods were first described in the Nineteenth Century, and there is some controversy as to how many broods there actually are. Most authorities, though, agree that there at least twelve broods of seventeen year cicadas and thirteen broods of thirteen year cicadas. The broods are dynamic communities influenced by changes in climate and habitat. A number of broods have died out since their initial descriptions while others have come into relatively recent existence.

Photo by J. Sturner Flickr

The name “locust” is unfortunately used to refer to these periodical cicadas. “Locust” is an ancient, Biblical name for the grasshopper. The plague of locusts that beset the Egyptians in Exodus consisted of swarming clouds of voracious, plant consuming grasshoppers that decimated hundred of square miles of crops and forage. Early European settlers in North America seeing the unexpected emergence of thousands upon thousands of these cicadas thought that they were observing a plague of Biblical proportions and so named the insect “locust.”

The adult periodical cicadas, though, feed only moderately on plant fluids and do very little damage to trees or other vegetation via their feeding. They are also unable to bite/sting or otherwise hurt a human being! Limb scarring from egg laying and larvae emergence can open some trees up to infections, but that too is usually without very much serious damage except in very young trees or in delicate, ornamental tree species like dogwoods. Blocking access of the gravid females to tree limbs (by cheese cloth coverings etc.) can lessened potential cicada damage to vulnerable trees. Even the larvae feeding on fluids from the roots of their host trees do not seem to greatly affect the overall health or rates of growth of the trees.

The following is a scenario for the upcoming emergence of the Brood VIII periodical cicadas. Brood VIII is the synchronized community of periodical cicadas found throughout the counties of Western Pennsylvania:

In June, 2002 female cicadas gathered in wooded areas that were filled with the incessant songs of the males. The loudest songs and the largest gatherings of singing males attracted the greatest number of receptive females. After mating, the female cicadas used their saw-like, posterior, abdominal appendages (their “ovipositors”) to dig under the bark of limbs of oak or hickory or dogwood trees. Into each of these gashes they laid one or two dozen tiny eggs. Each female then moved on to another limb and then another and another until they had deposited their six hundred eggs into roughly forty different sites.

Photo by J. Gallagher Wikimedia Commons

By August, all the adult cicadas were all dead. The eggs that hadn’t been eaten by birds or ants, or rotted by fungi, or destroyed by the summer heat hatched into tiny, ant-sized larvae that fell unnoticed to the ground. The larvae then burrowed six to eighteen inches into the forest soil where, among the tree roots that will sustain them, they began a slow, steady growth and metamorphosis that would last the next seventeen years.

In April 2019, these larvae, now nearly fully grown, begin to dig their way back out of their soil home. In May, they will pause about eight inches below the soil surface, waiting for the just the right weather to stimulate their emergence out through their soil turrets and mounds. A nice, warm rain is often the trigger that brings the soil temperatures to 64 degrees and initiates the cicada’s final climb up into the open air. Once up on the soil surface, the cicadas undergo a four or five day metamorphosis into their short-lived, flying adult forms.

In June, the rolling, buzzing, and some say, maddening, chorus of the seventeen year cicada will once again fill the countrysides and suburbs of Western Pennsylvania. Those individual cicadas fortunate enough (mostly via dumb luck and sheer force of numbers) to escape predation by birds, snakes, spiders, skunks, fish, moles and even dogs and cats, will reproduce and set up, for 2036, another generation and another extension of their “magical” life cycle.

 

 

 

 

 

 

 

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Signs of Spring 6: Mourning Cloaks, Commas and Spring Azures!

Mourning cloak. Photo by M. Nendov. Wikimedia Commons

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Last spring (Signs of Spring 3, March 15, 2018) I talked about the evolution of the Lepidoptera (butterflies and moths). Fossilized lepidopteran wing scales have been dated to over 200 million years of age! This is very significant because the flowering, nectar producing plants which make up most of our modern day lepidopteran food base did not evolve until some 50 million years later! What could those earliest lepidoptera have been eating? The logical answer to this question is actually on display in the early spring when several species of butterflies emerge weeks before the flowering of nectar-producing wild plants.

Mourning cloak butterflies (Nymphalis antiopa) over-winter as adults. They find cracks and crevices in tree bark and fold themselves into these narrow, protective spaces to spend the winter in hibernation. In the spring they emerge, often when there is still snow on the ground, and sustain themselves for several weeks during which they mate and lay eggs.

The emerging mourning cloaks vigorously contract their thoracic muscles to generate body heat. They also conspicuously and very uncharacteristically bask in the sunshine with their dark, colorful, dorsal wing surfaces (purple to maroon edged by an inner line of iridescent, blue spots and an outer border of yellow or creamy white) exposed to incoming sunlight. The venter (underside) of their wings is a dark, striated blackish-brown with a pale, gray border. Typically, the mourning cloak at rest folds its wings together so that only the drab, camouflaging coloration of the ventral wings is visible to potential predators.

These early spring mourning cloaks, quite possibly like those first lepidoptera 200 million years ago, drink sugar-rich tree sap that runs from wounds or woodpecker holes in trees. They are especially fond of oak trees and oak sap. The mourning cloaks are often seen walking head-first down tree trunks searching for oozes of sap. Adult mourning cloaks also eat rotting fruit and flower nectar during the summer and are especially fond of the flowers of knapweed and scabiosa (“pincushion flowers”). Mourning cloaks, like many butterflies, also swarm muddy puddles and even animal feces from which they gather not only moisture but also vital salts and nutrients.

Mourning cloak on lemonade sumac. Photo by M. Dolly

Mourning cloaks mate shortly after emergence from hibernation. Males typically select a sunny perch from which they watch for females. There is a brief courtship, and then the fertilized female lays from 30 to 50 eggs in encircling clusters on the small branches of some selected host tree or shrub species. These eggs hatch into small, black caterpillars that have white speckles and a very dark, continuous dorsal line.

The caterpillars are voracious eaters and readily consume the leaves of the American elm, aspen, cottonwood, hackberry, paper birch, and several species of willow. The caterpillars grow rapidly and undergo four molts as they move through their larval instar stages toward their inactive pupal stage. The pupa is encased in a gray chrysalis which hangs from a thread attached to branches or some other type of overhanging structure. The metamorphosis into adults takes about 15 days.

The eggs laid in early spring will pupate and emerge as adults by early summer (June or July). These adults may enter warm-weather inactivity phases (“aestivation”) and then re-emerge as the summer begins to fade. They then feed very actively in order to build up fat reserves for their hibernation. An individual experiencing this type of life cycle pattern may live up to 10 months or more! This makes the mourning cloak one of the longest lived butterflies in nature! These June or July emerging adults, though, may also, depending on the climatological conditions or levels of habitat resources, skip the aestivation phase and proceed directly to mating and egg laying. This second brood of eggs, then, hatches into caterpillars which grow, pupate and metamorphose into adults by August or September. This second brood, then, feeds voraciously to prepare itself for the long winter hibernation. In the northern sections of the mourning cloak’s range one or two of these seasonal broods are common. In the southern sections of the range, however, up to three brood generations can be seen.

The North American and European distributions of the mourning cloak are both expanding into more and more northern regions. It is thought that these expansions are yet another observation of the biological consequences of human induced global warming.

Comma. Photo by D. Dunford, Wikimedia Commons

Emerging along with the mourning cloaks are the comma butterflies (Polygonia spp.). The comma, like the mourning cloak, can overwinter as an adult and thus can quickly take advantage of warm spring afternoons to feed on the sugar-rich flow of tree sap or early flower nectars. This gives the comma a fast start on its spring reproduction. Commas are especially found in moist woods in which there is an abundance of nettles growing on the forest floor. Nettles, along with elm trees and hemp plants, are the primary plants on which the comma caterpillars develop.

The commas (also known as “angel wings”) are less distinctively marked than the mourning cloaks. Their orange and brown dorsal wing surfaces, though, stand out clearly against the browns and grays of the early spring vegetation. Like the mourning cloaks, the commas have very drab, very inconspicuously colored ventral wings surfaces. When they land and fold their wings, they seem to disappear from sight.

Commas, also like mourning cloaks, have summer and winter generations. The eggs laid by the over-wintering commas hatch into caterpillars that feed extensively on their nettle or elm host plants. The final instars of these caterpillar stages then pupate and form chrysalises from which a “summer generation” adult emerges. These summer commas are recognizable by the predominately black, dorsal surface of their hind wings. They feed widely on nectar, tree sap and rotting fruit and may, also like the mourning cloaks, spend the very hot months of the summer in inactive, aestivative states. They mate and lay their eggs again primarily on nettles and elms, and the caterpillars from these eggs will pupate and emerge as adults in the early fall.

These “winter generation” commas typically have hind wings that are predominately orange in color on their dorsal surfaces. These adults fatten up and then tuck themselves into tree bark spaces where they hibernate through the winter.

Spring azure. Photo by D.G.E.Robertson. Wikimedia Commons

Another early spring butterfly here in Western Pennsylvania are the tiny (1 inch across) spring azures (Celastrina ladon). These stunningly beautiful butterflies have neon blue dorsal wing surfaces that seem to glow as they fly about. When they land, though, and close their wings, like the mourning cloak and the comma, the bright color (and to all appearances, the butterfly itself!) disappears as the pale white under-wing colorations blend into the surrounding, early spring browns and grays. The spring azure unlike the mourning cloak or comma, though, overwinters as a chrysalis and finishes its metamorphosis into an adult as the winter starts to warm into spring. The spring azure is primarily a nectar feeder that emerges a bit later than the mourning cloak or the comma, ideally timing its appearance with the earliest blooming spring wildflowers. If plants are not immediately abundant, though, it may get nourishment, like the mourning cloak, from mud puddles, leaves and even bird and mammal feces.

The early butterflies of spring! In many ways a recapitulation of how butterflies lived in their first 50 million years! Slurping up tree sap and nutrients from mud and fecal sources. Waiting for the flowers to come!

 

 

 

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Signs of Spring 5: Early Spring on Rock Furnace Trail

Photo by D. Sillman

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Deborah and I went down to the Rock Furnace trail last Saturday around noon. It was cloudy but warm (65 degrees) and quite humid. The weather forecast was for a zero percent chance of rain, but it sprinkled on us off and on while we were walking. There was no one in the parking area when we arrived, but five other cars pulled in and parked while we were out on the trail.

Down below the trail Roaring Run cascades noisily through narrow channels of rock and then spreads out and slows as it enters wider parts of its gully. It flows east and then arcs north to join the smaller Rattling Run at the old, concrete bridge deep in the hollow. Rattling Run comes in via its picturesque drop over Jackson’s Falls just a quarter of a mile or so up a side-trail that is now marked private property. The abundance of snow and rain this winter has filled the springs that feeds these creeks. There is a lot of water running in the streams!

We paused on the trail just before the climb up to the McCartney #6 gas well and looked down across one of the wider parts of the stream. A chorus of spring peepers echoed up from below and cascaded around us. The first peepers of the spring!

Spring peeper. Photo by Fyn Kynd, Flickr

Spring peepers (Pseudoacris crucifer) are small tree frogs that live around marshes, ponds, temporary pools and small streams throughout the United States (except for the deep southeast). They are very abundant here in Pennsylvania. Peepers have sticky foot-pads that enable them to climb up the trees, shrubs, and tall grasses that surround their “home base” water sources, and it is from these perches that the male peepers sing out their distinctive, spring mating songs,

The peepers’ mating choruses begin in early spring (around here usually in mid-March). They usually start up fifteen minutes or so after sundown and typically go on for a four hour period. I am not sure why these peppers were calling so actively at noon last Saturday except that it was a cloudy day and finally warm enough for frog activity! Their release from the cold temperatures of recent days and nights probably stimulated the frogs into an out-of-character day-time chorus!

Female peepers, attracted to the calling of the males, enter the calling area and select the individual with whom they want to mate. The male then clasps himself onto the female’s back and remains there as the female return to the water source to deposit her eggs. The attached male prevents other males from mating with the female and insures that all of the female’s eggs will be fertilized by his sperm. The female can lay between 800 and 1000 brown-colored eggs either singly or in clusters. The eggs can be set afloat in the pond water, attached to submerged vegetation, deposited in the muddy bottoms of pools, or even put into fluid filled tree hollows or many other types of available micro-pools. Down along Roaring Run the eggs will probably accumulate in small pools around the rocks. Many will probably be eaten, though, by fish!

The eggs hatch in six to twelve days. The emerging larvae (the “tadpoles”) will typically remain in their aquatic form for ninety to one hundred days. This larval incubation period, however, can be as short as forty-five to sixty days depending upon weather conditions, time of egg deposition, and conditions in the tadpole’s pool.  The tadpoles eat a wide variety of foods (including algae, dead vegetation, bacteria, fungi, zooplankton, flesh from animal carcasses, and even inorganic materials like sand). The tadpoles are, in turn, preyed upon by almost any organism that is larger than they are. Fish are especially significant tadpole predators in ponds and streams, but predaceous beetles, salamanders, and water snakes also readily consume the tadpoles

We listened to the peepers for several minutes before we detected a second sound in the frog chorus. It was a sharp “quacking” croak of the wood frog! The longer we listened the more clearly the wood frog calls stood out. For the past seven years we have gone down to Ohiopyle in March to look for wood frogs. We were just down there the week before, actually! How wonderful to hear them so close to home!

Photo by D. Sillman

Everything is brown and gray along the trail. The forest floor is littered with dry leaves, and the gray tree trunks (mostly red maple, yellow poplar and beech) stand in dense copses, incredibly uniformly sized (8 to 10 inches dbh) all along the trail. These trees are secondary or maybe even tertiary recovery relics from the wholesale cutting  back in the Nineteenth Century that was needed to generate the charcoal that powered the old iron furnace whose remains can be found on down the trail. There is also a stand of eastern hemlocks that may be a remnant of the hemlock forest that probably dominated this cool, wet ravine before the iron furnace was set up. Out in the surrounding acres of hardwood trees, occasionally a young hemlock can be found growing all by itself. These small trees are probably surprisingly old! If they last another three or four hundred years and actively drop their cones and seed around themselves, those hemlocks will be centers of ecological hemlock “crystals” that will reshape this forest back into a pure hemlock stand. All of the maples, beech and poplars that we see today, then, will then just be distant memories in the humus.

Photo by D. Sillman

It’s easy to spot the hemlocks. They are bright stabs of green in the brown and gray of the forest. Looking closer I see other patches of green, too. Evergreen wood fern, Christmas fern and polyploidy fern up on the sandstone boulders have kept their chlorophyll all winter. Many of the rocks and some of the fallen logs and stumps also have mosses growing on them. Many of the moss mats have recently sent up sporophytes (they are so new that they are still green!). The knobby sporangia on the tips of the sporophyte stalks will make spores that will disperse in the wind or in the rain and let the moss mat slowly increase its density and steadily expand its edges.

Spring beauty. Photo by D. Sillman

Spring beauty is in bloom! Its delicate little white flowers are hard to see at first, but once your eyes adjust to their presence they light up the forest floor. Chickweed is also in flower. Cut-leaf toothwort (“pepper root”) plants are up and in leaf but not flowering yet, there are also many violets that have not yet set flower buds. Interestingly, the usual “first flower” of spring, coltsfoot, is no where to be seen. There is a south facing trail-cut just opposite the McCartney gas well at the top of the hill where the first coltsfoot is almost always seen. No hint of its yellow flowers today, though.

There are drainage ditches alongside the trail that are full of still water. Often these ditches have salamander and toad egg clusters in the spring. Today, though, the water is clear and there are no egg masses.

It  is barely spring down on Rock Furnace Trail! All of the plant and animal signs of spring seem to be so much later this year than usual. Once we hit some warm weather, though, the pace of “spring-change” will be hard to keep up with!

 

 

 

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Signs of Spring 4: Bumblebees and the Pursuit of Happiness (and More!)

Photo by D. Sillman

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Emotions are hard to quantify and have been a difficult area of research in non-human subjects. Long standing cautions against anthropomorphic explanations or descriptions in animal behavior studies have only recently been modified in large part due to pioneering behavioral studies on several of our most closely related primate species. As Frans de Waal put it in his July 1997 article in Discover magazine (“Are We in Anthropodenial?”): “To endow animals with human emotions has long been a scientific taboo. But if we do not, we risk missing something fundamental about both animals and us.”

Even Charles Darwin, the standard of objectivity and clarity for most of the biologists I know, wrote of emotions like love and joy in the animals he observed. Later interpretations of his writings, though, often alleged, without any direct, corroborating evidence, that he was he was using these terms metaphorically.

Anthropomorphism is a powerful tool, and it must be applied carefully. Otherwise we could easily end up with cartoon-like images of the animals we were studying. This would not only obscure reality, but it would also would demean and degrade the non-human species around us.

I talked about emotions like love and happiness in last week’s blog. They were the physiological and evolutionary impetus for the formation of groups, and they were the products of hormones and brain neurotransmitters creating an existence matrix within which an organism feels content and safe (i.e. “happy”) or anxious and stressed (i.e. “unhappy”) due to the physical, visual, auditory or olfactory contacts (or lack thereof) with other members of that organism’s species. These contacts flood the herding animal or potential herding animal’s brain with soothing neuropeptides and generates a tangible force for the “pursuit of happiness” that is full of ecological and evolutionary implications!

Bumblebee. Photo by Alvagaspar, Wikimedia Commons

Some researchers are extending these models of happiness into groups of insects. Bumblebees, for example, display a number of behaviors that can be interpreted as happiness or optimism especially in response to sugar-rich treats and rewards!

Experiments by Clint Perry and colleagues at the Bee Sensory and Behavioral Lab at Queen Mary University in London were published a few years ago in Science (September 30, 2016). Perry and his co-workers trained bumblebees to fly through a blue colored portal (rather than an adjacent green portal) in order to receive a sugary treat. After the bumblebee had gotten its sugary reward the experimenters then put the bees into an experimental chamber that had portals painted with an ambiguous color (purple). They found that the bees that had received the sugary treat were more likely to fly through the new colored portals than those that had not received any sugar. The researchers interpreted these data as evidence that the sugar-rewarded bumblebees had an elevated sense of optimism about the possible consequences of flying through the new type of portal.

In a second experiment, the Queen College researchers simulated a spider attack on a bumblebee (an event that does occur on flowers visited by the bees). The simulation involved a clasping device that temporarily held onto the bee by its leg. They found that bumblebees that had had a sugary treat prior to the “attack” recovered from the trauma of the attack much more rapidly than those bumblebees that had not had any sugar. The researchers interpreted these data as also indicating an increasingly positive, optimistic mind set in the sugar treated bumblebees.

Dopamine is a brain neurotransmitter typically associated with pleasure and reward. Dopamine is found not only in the synapses in mammalian brains but also in the synapses in insect brains and ganglia. When the above experiments with bumblebees were repeated using bees that had been given a dopamine blocking drug none of the positive (“optimistic”) effects of the sugar rewards were observed. These results supported the hypothesis that the sugar reward stimulated dopamine production which then caused the bumblebees to be in a more positive, optimistic state which then led them to more freely explore their environment and recover from the trauma of a simulated predator attack. These bumblebees, then, were happy!

Photo by R. Moehring, USFWS, Flickr

Researchers at Queen Mary University are also looking at bees in other ways. Recently, they explored the remarkable plasticity of a honeybee’s DNA and published their results in Genome Research (August 22, 2018). All of the individual honeybees in a hive have identical DNA, but many of the individual bees have very different appearances and functions within the hive. The differences between the different castes and functional types of bee begin almost immediately as an egg hatches into a larva. Nurse bees (one of the specialized types of worker bees) feed the newly hatched larvae specific foods that alter the histone proteins in the larvae’s DNA. These histone epigenetic changes, then, regulate the subsequent expression of the larvae’s genes and control their development into a specific caste or functional class of worker.

A few years ago a paper published in Nature Neuroscience (September 16, 2012) demonstrated that some of these epigenetic changes that regulate the formation of the functional types of workers are reversible. Nurse bees in a hive could change into foraging bees in matter of a few hours depending on the specific group needs of the hive community. Further, foraging bees could likewise be changed into nurse bees if the hive’s functional economy demanded it. All of these changes were mediated through the methylation and demethylation of the histone proteins around the bee’s DNA and the altered specific activity of the genes that coded for these functional roles.

So dopamine makes bumblebees happy and optimistic enough to go exploring for food and rewards. Nurse honeybees mix concoctions that alter the shape and expression of the individual larvae’s DNA and cause those individuals to develop into different castes and functional workers. And, if the needs of a hive begin to change and greater demands for pollen and nectar gathering or rearing of the young arise, these same concoctions can alter the activity of grown bee’s DNA and cause them to take on different roles in the hive.

Bees are amazingly elegant animals!

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Signs of Spring 3: Living in Groups

Caribou herd, Photo by USFWS, Public Domain

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There are many names for groupings of animals. A “herd” is usually a group of mammals with some sort of hierarchy and intra-group communication system. A “flock” is a similar type of association made up of birds (although “flocks of sheep” are the common descriptor possibly because of old language rules). There are also “schools” of fish and “prides” of lions and “packs” of wolves or dogs. A number of specific types of herds and flocks have very peculiar, historically derived names: there are knots of toads, parliaments of owls, basks of crocodiles, murders of crows and many more!

We recognize, then, that many animals live in groups, and we can pretty easily recognize the benefits to those animals of their grouping behaviors. A herd or a flock can cooperatively find more food than a single animal is able to locate. In cold environments a group sleeping very closely together helps to keep the individuals warm and contributes significantly to each individual’s overall energy efficiency.

Individuals in a group may also share information about the group’s immediate environment or about previous occurrences or methods of solving problems of food acquisition or individual survival. In some species a “culture” can actually develop where unique behaviors are passed along from one generation to the next. A number of bird species (like American oystercatchers and crows, for example) have specific flocks with very specific hunting and foraging patterns. In some of these groups even threat recognition memories are passed along from one generation to the next (see Signs of Summer 7, July 14, 2016).

Most obviously, a group achieves a significant degree of protection from predators. This protection can come about relatively passively by a tendency to keep the youngest and thus most vulnerable and most frequently preyed upon members of the herd  in the middle of the group,  or more purposefully and even cooperatively, by the stronger individuals of the herd aggressively placing themselves between their vulnerable young and a potential predator. Protection can also be achieved via a variety of “selfish herd” behaviors or through the intimidating effects on a predator confronting a large, moving mass of animals in which individuals are very hard to discern or single out.

Wildebeest herd. Photo by B.C.Torrissen, Wikimedia Commons

A study on lion prides and wildebeest herds in the Serengeti published in Nature in 2007  (Volume 449, October 25, 2007) showed another benefit of both prey and predator group formation: the establishment of long-term ecosystem stability. Large prey herds had losses to predators that were 90% less than losses from smaller groupings of prey individuals. Predator groups (the lion prides) took in less prey energy, but did not over-exploit the prey populations. They achieved, then, via increased intraspecific competition and reduced rates of reproduction, a sustainable relationship with their prey.

There are also some negatives associated with living in a  group like increased competition for food (although as we see with the lions that increased competition may have unexpected benefits to the ecosystem of the grouping species). There is also increased competition for mates and increased difficulties finding unoccupied, optimal sleeping/resting sites. There is also increased exposure to and likelihood of transfer of any number of diseases and parasites. A large herd of individuals is also much more visible in their environment than small, scattered clusters of individuals. Predators can quite easily locate a large herd of potential prey, but as we see in the lion/wildebeest study finding the herd does not necessarily mean taking more prey.

So, groups of animals are easy to observe, and their individual and group benefits (which must, of course, outweigh the potential detriments) are easy to infer. Logically, these grouping behaviors are the products of evolution. In a natural selection system individuals that had a genetic predisposition  to form a group would have higher rates of survival, more metabolic energy and greater numbers of offspring. Over time, those genes that stimulated group formation would predominate in the population and a herding or flocking or schooling species would be formed.

The more subtle question here, though, is what exactly are those genetic features that would cause some starter species to form a group in the first place?

Pituitary gland and hypothalamus. Image by Open Stax.

Hormones seem to be a significant part of the answer here. In particular two neuropeptides that are synthesized in the hypothalamus of the brain and then transported via specialized nerve fibers to the posterior pituitary gland or released into the brain itself. Those peptides that go to the posterior pituitary subsequently enter the blood stream where they go out to influence target organs in the body. The peptides that stay in the brain influence a number of specific gray matter regions that play a significant roles in the tendency of an individual to form social bonds and carry out the kinds of cooperative behaviors that can make a group successful. The two neuropeptides are vasopressin (also called “antidiuretic hormone”) and oxytocin.

Vasopressin has very straightforward hormonal effects on the body: it stimulates water re- absorption in the kidneys (thus fighting dehydration) and causes arterioles to constrict (thus raising blood pressure). In the brain, though, its impacts are more subtle. It influences social behavior centers especially ones that stimulate an individual to participate in mutually beneficial behaviors (see February 23, 2016 Proceedings of the National Academy of Sciences). It may also help to modulate the body’s stress response and the subsequent synthesis of stress hormones like cortisol and adrenaline.

Photo by Pixabay.

Oxytocin also has very straightforward hormonal effects on the body: it stimulates the uterine contractions of labor and smooth muscle contractions in the breasts that releases milk (the “let down reflex”). In the brain, though, oxytocin stimulates pair bond formation, social affiliations, and, in general, shifts the individual from an emphasis on self-interest to an interest in group affiliation.  Oxytocin is sometimes referred to as the “love hormone.”

So, in a natural selection cycle, a population of a potentially group forming species would have some individuals with very developed “social brain” receptors for vasopressin and oxytocin. Those individuals would experience positive emotions and reduced stress when they were in physical, visual, olfactory and/or auditory contact with other members of their species. They would, then, be stimulated to form a group in order to maximize these positive emotions and would then reap the wide range of potential group benefits. These benefits would then drive the selection matrix and multiply and conserve these genes in the future gene pool!

So what happens to an animal that has these group selection neuropeptide features but is kept in isolation from individuals of its species? The animal becomes stressed, depressed and anxious. It may become so depressed and stressed that it stops eating and may even die. This happens to parakeets (companion parakeets or even a mirror to generate a comforting reflection are requirements for keeping one of these very social birds), it happens in sheep, it happens in cows, it happens in tropical fish, it happens in many zoo animals and it happens in the species that may have derived the most significant ecological and evolutionary benefits from group formation in all of Kingdom Animalia, humans. A human being removed from its group inevitably experiences a wide range of mental health issues revolving around their unregulated and untended social brain chemistry.

Sebastian Junger talks about this in his marvelous book Tribe: On Homecoming and Belonging. Junger talks of the “tribes” we form in our lives and the consequences of their dissolution. Family groups, sports teams, military units and groups thrown together under conditions of stress and pain are all explored in the context of the human ability (that single most significant ability, according to Yuval Harari in his books Sapiens and Homo Deus, that has led humans to come to dominate the Earth!) to form groups. Depression, stress and other mental maladies are the consequences of our not paying attention to the evolutionary pathways that have created us.

 

 

 

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Signs of Spring 2: Daylight Savings Time

Sunrise over the Mojave Desert. Photo by J. Eastland. Wikimedia Commons

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Last weekend we changed over to Daylight Savings Time (DST). The “spring ahead” change in our clocks does nothing to alter the total amount of daylight we get in a day, but it does change our perceptions of lengths of day and night. Supposedly, we quickly compensate for our lost hour of sleep on that first Sunday morning after the time change, but many of us, I am sure, spend that day and the next night (and maybe a few more days and nights after that) feeling edgy and groggy. Most of us will return to “normal” in a few days, although I did have a roommate at college who took weeks to recover from either the spring or fall time changes.

All sorts of studies have explored the impacts of the fall and spring time changes The fall, with its promise of an extra hour of sleep, seems more benign than the spring change which takes that hour away. One researcher referred to both changes, though, as a type of “jet lag.” Sleep pattern disruptions, headaches, and mood changes were the dominant symptoms, and like jet lag the symptoms fade within a few days.

The spring change, though, has some potentially serious consequences: for several days after the “spring ahead” clock change there are increases in work-related injuries, and, possibly (although there are conflicting data on this) an increase in morning traffic accidents. Interestingly, according to a 2012 study published in the Journal of Applied Psychology, for several days after the spring time change office workers also increased their on-the-job “cyberloafing” Internet time. Maybe web surfing is an adaptive way to avoid accidents and injuries!

Mornings are suddenly darker than they were. We have been on a steady march to more and more sunlit hours and minutes ever since the sunlight minimum (nine hours and sixteen minutes and fifty-six seconds) of the winter solstice last December 21. Today (March 14) there will be eleven hours and 51 minutes and 56 seconds of sunlight, and thanks to DST most of those added 155 minutes of sunlight will be visible in the late afternoon and early evening. My neighbor is very excited to have later sunsets. She regularly sleeps through most of the morning hours, and the time change makes the waking part of her day much more sunny and useful! It is, however, no fun to walk a dog in the cold morning by flashlight. We are all pleased, though, to be moving toward the Summer Solstice on June 21! We will have 15 hours and 3 minutes of sunlight that day. That will be plenty to go around for both sunlit mornings and evenings.

Silver maple in flower. Photo by D. Sillman

Anyway, our shift to DST does not affect organisms other than humans, but the on-going increase in the ratio of light to dark minutes during a day  does affect almost every plant and animal species around us. The flower buds on the silver maples and the red maples are swelling and will burst open possibly in just another week. The male bluebirds are getting cranky with each other and are partitioning off the territory they had willingly shared through the winter. Migrating males are also arriving making the territory partitioning even more intense. Our summer migrants (the tanagers, grosbeaks, buntings and orioles) have felt the daylight changes, too, and are starting to gather themselves for their long flights north!

Where did DST come from?

Painting by J. Duplessis. Wikimedia Commons

Most histories on the subject start with Benjamin Franklin and his letters to the French authorities in Paris describing the inefficiency of unused daylight in the early morning and the “candle cost” of the early darkness in the late afternoon and early evening. Shifting clocks ahead by an hour, he contended, would more appropriately align the available daylight hours to the activities (and candle usages) of the citizens of Paris.

In World War I Germany shifted its national clocks to extend the daylight period into the evening in an attempt to save energy, and quickly other nations of the world on both sides of the conflict did the same. Retailers in large cities noticed that more people were out walking (and shopping!) on the days with extended afternoon sunlight and lobbied to keep DST after the war. Similar energy arguments were made in World War II and the seasonal return to DST became institutionalized in many national cultures. In fact, the most cogent argument in favor of DST is that it stimulates the consumer economy. Farming interests were quite opposed to the shift to DST and the attempts to portray it as a benefit to farmers are tortuous in their logic and foundations.

In the United States the passage of the Uniform Time Act of 1966 required states to conform to their respective Standard Time zones but allowed them some flexibility with regard to DST. Only Arizona, Hawaii and Puerto Rico, however, have opted not to “spring ahead” into DST each March. There are also several states that have made attempts to make DST a permanent, year-round clock setting although the Uniform Time Act does not allow states the freedom to make these type of changes. It is argued by the permanent DST advocates, though, that shifting daylight minutes and hours into the more highly used afternoon and evening time periods is a better use of sunlight resources. As one DST researcher put it “everyone loves DST!”

Does DST save energy?

Photo by Pixabay

The simple answer is “yes and no.” Less energy is used for artificial lighting (Ben Franklin was right about the potential “candle” savings!), but more energy is used for almost everything else! People waking up in the cold, dark early morning hours use considerable amounts of energy for heating. People taking advantage of the extra daylight in the afternoon and evenings are most likely to drive somewhere (a park or a mall or a shopping district) to enjoy the extra sunlight (and gasoline usage does increase when DST is introduced). Also, air conditioning usage goes up in the warmer afternoons and evenings. A 2006 study in Indiana found that electricity usage increased by 1% when DST was  introduced (estimated cost: $9 million!).

As I said at the beginning of this essay, the shift to DST affects humans but not the plants and animals around us (except for our poor dogs, of course, who now have to do their morning walks in the dark). This fact, though, is not always clear to people who, understandably, have a difficult time grasping just how the idea of “an hour more daylight” is actualized. Concerns have been raised that this extra hour will cause lawns and crops to wither and die, and that it will so disrupt the feeding and activity schedules of farm animals that milk production, egg laying and meat production will suffer. Possibly even wild birds will begin to migrate or nest at inappropriate times just because of this “unnatural” disruption of our clocks.

Anyway, most of us will stop noticing the time change in a day or two. I also guarantee you that the birds out in our yards and fields and the other animals out in our woods never noticed any of these changes to begin with!

 

 

 

 

 

 

 

 

 

 

 

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