Signs of Summer 9: Summer Signs

Photo by D. Sillman

Photo by D. Sillman

Deborah and I have been keeping our eyes on some of the biological and ecological “events” of the summer of 2016. Since we have just slipped past the halfway point of the season, it’s time to think about some of these.

We have had some very successful reproductive efforts by the birds that visit our feeders and leaf piles! The cardinals and the robins have each had two nesting and fledgling cycles so far and seem to be starting up on another (both are out gathering new beaks-full of grasses and stems for their nests!). The chickadees and titmice have also gotten two nesting cycles done but seem to be less inclined than the cardinals or the robins to start into a third. The Carolina wrens also went through their usual mate re-shuffling kerfuffle in late June and have settled into a second nesting period.

Photo by D. Sillman

Photo by D. Sillman

The common grackles arrived at our feeders late in the spring, but they must have nested and fledged their young very quickly because there is now a robust flock coming to the feeders dominated by a large percentage of dark brown, immature birds. They swoop into the feeder areas about 10 am and especially like the scattered shelled corn (which they frequently dunk in the water of the bird bath before eating!).  I am very tolerant of the grackles and put out extra corn for them at mid-day. I remember them voraciously eating gypsy moth caterpillars back in the gypsy moth explosion years of the 1990’s and want to continue to thank them for their efforts!

Photo by D. Sillman

Photo by D. Sillman

The blue jays and crows have completed their single nesting efforts and are now leading their fledglings around our complex habitats drilling them on food finding protocols and safety procedures. The first and second robin fledglings have gone from stumbling klutzes tripping through the leaf piles to confident, elegant hunters and efficient spearers of worms and caterpillars.

The mourning doves seem as though they have been mating all summer! I have lost track of how many nesting cycles they have gone through! The sharp-shinned hawks mated back in the late winter (the female was, as usual, extremely loud calling from the bare branches of our backyard black locust tree). Early in the morning we frequently see a sharp-shin swooping across the top of the front yard bird feeders. We also frequently find small piles of feathers (usually doves or cardinals) around the edges of our field. We have never seen, though, a sharp-shin fledgling! They are said to be secretive birds during reproduction and very wary of larger hawk predators (like goshawks and red-tails).

So, most of the birds seem to be behaving quite normally for a Western Pennsylvania summer, but many of the insects and other arthropods are acting quite oddly this year and they may be having some impacts on a wide variety of other species!

Aedes albopictus Photo by J. Gathany CDC Wikimedia Commons

Aedes albopictus Photo by J. Gathany CDC Wikimedia Commons

For example (and we are not complaining about this at all!), we have fewer mosquitoes around our house this summer. We are regularly sitting out on our deck well into the evening with minimal aggravation from buzzing and biting mosquitoes. These longer deck times, though, possibly go along with seeing fewer chimney swifts and fewer bats soaring over our field gobbling up all sorts of flying insects (but especially great numbers of mosquitoes!). The hummingbirds also came into our yard quite late this summer (they waited until the lure of the flowering bee balm in Deborah’s flower bed was overwhelming!). Hummingbirds are frequently described as “nectar powered insect eaters.” Possibly the lower numbers of mosquitoes reduced the feeding quality of our yard and field for the hummingbirds and caused them to linger elsewhere until the nectar scents were just too compelling!

Photo by JJ Harrison Wikimedia Commons

Photo by JJ Harrison Wikimedia Commons

Also, and we are not complaining about this either, there were no little “sugar ants” in the kitchen this spring! Every other May and June that we have been in this house (and in one week we will celebrate the 27th anniversary of our house closing!) we have had several weeks, at least, of columns of ants streaming in through tiny cracks around the kitchen window and door in search of any available crumbs or sticky residues. This year the ants did not show up! We think that these ants are mostly odorous house ants (Tapinoma sessile), but they may have been joined in bumper ant years, by the European exotic species called the pavement ant (Tetramorium caespitum).  They are both little black ants that may fall into the very broad, common category of “sugar ant,” but one of them (“odorum”) gives off a bad smell when it is crushed.  We seldom crushed any of them, but frequently washed a number of them down the drain.

Another insect change this year is a very small number of brown marmorated stink bugs (Halyomorpha halys ) emerging from their winter, in-house hibernations.  Again, we have no problems with the direction of this change! I talked about this earlier this summer (Signs of Summer #3, June 16 2016). The lower numbers may be due to the growing activity of the predators of stink bug adults and eggs. Everything from spiders and chickadees to earwigs and katydids are now eating these exotic pests.

Photo by D. Sillman

Photo by D. Sillman

And finally, another arthropod that is less numerous and less active in our summer of 2016 ecosystems is the deer tick! We have had, along with most of Pennsylvania and much of the northeast, huge numbers of deer ticks in our rural and suburban ecosystems. These ticks are the arthropod vectors that spread the bacterium that causes Lyme disease, and as a consequence of their large numbers, Pennsylvania has had for the past few years the greatest number of Lyme disease cases in the country. Our yard and field have been a rich reservoir of these ticks. Walking out in the yard in sandals almost guaranteed you a tick or two, and our dog, Izzy, and our cat, Mazie, weekly (and sometimes daily!) picked up deer ticks from their forays within the fenced-in yard off of our deck. This spring and summer, though, we have found no deer ticks on either humans or pets! Further, our trampling around at Harrison Hills Park to check our bluebird houses also has not generated any ticks (a big change from last year!).

I am not sure why, and would like to ask everyone reading this post to think about your tick experiences this summer. Have you seen any deer ticks as a consequence of hiking or yard work or dog/cat interactions? Are we seeing some change in our deer tick populations?

Wow! Pennsylvania will surely get crowded with people if we start to have mosquito free and tick free summers! Real estate prices will go up! House sales will increase! Nothing but good things (unless you like chimney swifts and bats, of course).

More on all of this soon! Happy summer, everyone!

 

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Signs of Summer 8: Cavity Nesting Team!

Photo by D. Sillman

Photo by D. Sillman

Last year I wrote two blogs about our Cavity Nesting Team study up at Harrison Hills Park in northern Allegheny County (May 28 and October 29). We had a very good year with our bluebirds and tree swallows. We had 13 boxes that had bluebird nests with a total of 65 eggs and 48 fledglings (a 74% survival rate), and we had 9 boxes that had tree swallow nests and a total of 31 eggs and 22 fledglings (a 71% survival rate). Nine of our thirty nest boxes, though, did not have any nesting activity, so, using our locations of utilized boxes as a guide, we relocated seven of these inactive boxes to try to make them more attractive to cavity nesting bird species. We left two of the inactive boxes in their 2015 locations because they seemed to be in ideal spots for cavity nesting birds (we must acknowledge, however, that we were wrong about their ideal locations! (see discussion below)). Our overall criteria for relocation were quite straightforward: boxes too close together tended not have nests (so spread out the clumped together boxes) and boxes right on the edges of field (i.e. very close to surrounding woodlands) were not used (so move the boxes away from the extreme edges of our fields).

This year’s Cavity Nesting Team consists of eight volunteers: Deborah and I and Sharon Svitek take turns monitoring the boxes in and around the “High Meadow” area of the park. Patrick and Mardelle Kopnicky check the boxes around the “Bat House Meadow.” Chris Urik and Odessa Garlitz take turns monitoring the boxes at the park entrance and up in the field near the Environmental Learning Center, and Paul Dudek checks the boxes around the pond and soccer fields in the southern end of the park. Every box is checked each week, and then each observer enters their data into an on-line Google spreadsheet. Each week, Deborah compiles and distributes the growing data tables to each member of the team. Chris Urik also has made GPS maps of the park showing the precise location of each nesting box.

Photo by D. Sillman

Photo by D. Sillman

As I talked about last year, native cavity nesting bird species (eastern bluebirds, tree swallows, house wrens, Carolina wrens, titmice, chickadees, nuthatches, etc.) naturally use tree holes for their nesting sites. These holes are typically found in older, often dead trees and are frequently abandoned cavities that have been chiseled out by woodpeckers. Any site management plan that favors woodpeckers (allowing dead trees to remain in the forest and not managing the forest or manipulating it into an even aged stand) will favor cavity nesting bird species.

Nest boxes are artificial substitutes for these natural tree holes. Eastern bluebirds, in particular, came under a great deal of stress in the past century. The influx of the alien invasive English sparrows and European starlings along with the habitat spread of the nest parasite, the brown headed cowbird, were major reasons for the bluebird’s numerical and distributional decline throughout the twentieth century. Human destruction of nesting and feeding habitats also contributed to this decline. Human efforts to provide existing bluebird populations with suitable and secure nesting sites (“bluebird boxes”) have, however, been extremely successful in bringing this beautiful species back from the brink of possible extinction. The North American Breeding Bird Survey reports that since 1966 eastern bluebird populations have increased by nearly two percent a year! The Cornell Laboratory of Ornithology estimates the worldwide population of eastern bluebirds (80% of which spend at least some time in the United States) at a very robust 22 million individuals.

K. Thomas, Public Domain

K. Thomas, Public Domain

We are just past the halfway point of the summer, but our nest box data is showing some very interesting trends. First and foremost, our strategy for moving the inactive nest boxes has been very successful. All seven boxes that we moved have had nesting activity this spring and summer! Five of them have had bluebird nests (and have generated 13 bluebird fledglings), one box had a successful chickadee nest (4 fledglings), and one had a tree swallow nest (with eggs, nestlings and fledglings that were too hidden in the nest materials to count). Further, four of these nests were then utilized by house wrens (although it seems these secondary nests did not produce any viable fledglings). The two inactive boxes from 2015 that we did not move (because they just seemed like PERFECTLY located boxes!) still did not have any nesting activity. We need to look at these two locations more closely to try to see why they were not utilized by any of our cavity nesting species! We need to learn to think more like bluebirds and swallows!

So far this summer 17 of our boxes have had bluebird nests (with 61 eggs and 45 fledglings). These numbers are almost equal to the totals from all of last year, and we are just coming into the second wave of the bluebird nesting and reproduction! We expect to significantly surpass last year’s egg and fledgling totals for bluebirds!

K. Thomas, Public Domain

Tree swallow, K. Thomas, Public Domain

Our tree swallow numbers, though, have been less robust than last year. Only six boxes have had tree swallow nests and there have been only 9 confirmed fledglings (although two nests did have nestlings that we expected did fledge, but the nest construction prevented direct observation of the birds. Even so, the 9 fledglings (even plus the 6 or 7 that might have come from the concealed nests) is well below the 22 fledglings we observed in 2015. Tree swallows have been described as “income” breeders that base their timing of reproduction on

Photo by dfaulder, Wikimedia Commons

House wren, Photo by dfaulder, Wikimedia Commons

short-term rates of food intake near the time of breeding. Reduced clutch size in tree swallows is a strategic response to limited resource abundance. Since the primary food of nestlings are adult insects that have aquatic larvae possibly some factors (weather? water quality? something else? ) have reduced the abundance of these insects and the tree swallows have responded by curtailing reproduction. It is also possible that the increased abundance and nesting activity of the house wrens has affected the tree swallow nesting and reproduction efforts. House wrens are known to actively interfere with the nest box selection and nesting activity of tree swallows.

So the cavity nesting cycle continues! We will keep monitoring these boxes on through Labor Day. I will let you know our final counts and observations!

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Signs of Summer 7: Watching Crows

Photo by D. Sillman

Photo by D. Sillman

The American crow (Corvus brachyrhynchos) is a large, loud and obvious avian species that inhabits a wide variety of habitats throughout Western Pennsylvania.  They were recently featured on the cover of the March/April 2016 issue of Audubon magazine (the bird equivalent, I am sure, of a musician being on the cover of Rolling Stone!). The articles in this issue focused on a number of studies that evaluated the intelligence and individual and communal memories of crows.

For example, John Marzluff at the University of Washington in Seattle went out in the 1990’s and caught and banded (and then released) a cohort of crows. Marzluff and his banding team wore “caveman” masks while they were netting and banding the crows. Subsequently, Marzluff and his team returned to the crow banding area and were ignored unless they wore their caveman masks (even Dick Cheney masks did not elicit a violent crow response!). Not only did the crows that had been directly captured and handled by the caveman scientists remember and react to the caveman masks, but also their fellow flock (or “murder” as a crow flock is called) members quickly learned the caveman face and joined in on the mobbing and commotion. Marluff’s team regularly returns to this crow territory and, although it has been over ten years since the initial trapping event and the originally trapped crows are now undoubtedly all dead and gone, the flock still responds in what the article labels a “crowpocalyspe” whenever the caveman masked researchers return.

Photo by D. Sillman

Photo by D. Sillman

These studies (along with some remarkable brain activity analyses using PET scanners and radioactive isotopes) not only show the individual crow to be extremely intelligent (Mazluff calls them “flying monkeys!”) but also highly connected within its flock to a communication and information system that has to be defined as a culture!

Crows are seldom seen alone. In the non-breeding part of the year (fall through the winter) they form large, communal flocks of hundreds to thousands of individuals. Increasingly these large, winter flocks can be found in urban areas (much to the distress of the area’s human residents!). Lancaster, PA, for example, had 20,000 overwintering crows in its Park City Mall a few years ago, and a number of towns in Pennsylvania have faced the loud (and messy) problem of large flocks of winter roosting, “urban” crows! The warmth and lights of the city environment and the protection it brings from great horned owls and other crow predators are thought to be some of the factors that are selecting for these urban-centered crows. During the breeding season (spring to late summer) crows form smaller, more cohesive, familial flocks, that break up into even smaller foraging groups that daily travel out across the countryside looking for food.

Photo by D. Sillman

Photo by D. Sillman

Communication between individuals in the foraging groups and within the larger flocks is a very important aspect of crow biology. The remarkable and extensively documented intelligence of crows (their ability to solve food-gathering problems, to learn to mimic human vocalizations, to employ a variety of complex strategies to gather food etc.) is thought to be a direct extension of their evolutionary success as a social, highly efficiently communicating species. Crows, by the way, have longer rearing and nurturing periods than other bird species. These “learning periods” are even longer than those observed in many mammals! These nurturing periods can last up to a year and a half and enable the parental generation to communicate extensive amounts of very functional survival information (hunting and foraging strategies and techniques, habitat selection preferences, etc.) to their offspring.

American crows can be found residing in or moving through a great variety of ecological habitats. They seem to prefer a broad functional range that includes both fields (for grasses and seeds and for small vertebrate and invertebrate prey species) and woodlands (for night roosts and for protection). Human agricultural systems are especially favored by the American crow. Their negative impacts on grain crops can be extensive. It is estimated that in the United States the American crow population numbers over three billion individuals! Many states (including Pennsylvania) allow hunting of crows to try to control their numbers.

Crows eat a great variety of foods. Invertebrates (like grasshoppers, grubs, earthworms, and caterpillars) are consumed as they become seasonally abundant. Vertebrates (bird eggs, small birds, rodents) are eaten opportunistically or may even be actively hunted. One spring, a few years ago, out in my side field, I observed a crow swooping down on a low flying female northern cardinal. The crow slammed down on the cardinal striking it with its chest and knocking it to the ground. The crow then landed next to the dazed, but still moving cardinal, picked it up in its beak, and flew off with it. Several other crows followed close behind, and the whole group was loudly pursued by five or six blue jays. I have in the past also observed crows picking off young red squirrels as they walked in line along a tree branch behind their parent.

Photo by D. Sillman

Photo by D. Sillman

Crows also eat carrion and are active scavengers of human garbage. Crows utilize their excellent vision to find and obtain their food. While hunting and feeding individuals of the flock take on specialized jobs (some functioning as lookouts, for example, while other members of the flock feed). Vocal communications between individuals of the flocks are critical to the overall success of the foraging group. Complex hunting behaviors have also been observed in crows. Some these include mobs of crows driving rabbits from a field across a roadway. A few of the driven rabbits were hit by cars and were then eaten by the crows. Crows have also been observed actively interfering with other predators (like river otters) to distract them from their captured prey which the crows then appropriate for their own consumption. These behaviors are further examples of the group dynamics and extreme intelligence of this remarkable species.

I have written before about “my” crows. There are three crows that wait for me each morning to come out and dump a couple of handfuls of peanuts under my bird feeders. They watch me from surrounding tree tops, excitedly caw when I carry out my bucket of birdseed, corn and peanuts to fill my feeders, and often swoop down to start picking up and swallowing as many peanuts as they can (as fast as they can) even before I get back to my front porch.

Crow populations have been increasing all around the world. Some researchers speculate that this incredibly adaptable and intelligent species is benefiting from the ongoing population declines in most of the more specialized avian species. The adaptable, generalist crow can occupy many niches in an ecosystem. We will undoubtedly be seeing a lot more of them in the coming years!

 

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Signs of Summer 6: More on Bees

Photo by I.Tsukuba, Flickr

Photo by I.Tsukuba, Flickr

I had an email from a friend a few weeks ago asking me about the impact of lawn mowing on bees. Since I regularly mow a one acre field that is a complex mix of grasses and flowering plants, I have had some experience adapting my mowing to the populations of bees (and other pollinators) that visit the flowers throughout the summer. I also wanted to check the literature to see if there had been any published papers about the impact of mowing on bees.

It is important to note that most people mowing suburban lawns won’t have any significant interaction with bees or other pollinators because their lawns are pollenational deserts. It’s a good news/bad news thing! The expanses of  single grass species that are so carefully and expensively manipulated into flat green carpets have no plant species that would attract (or feed and nurture) pollinating insects. So for any of you managing one of these ecological disaster zones, you don’t need to worry about your mower interacting with bees.

For people like me, though, who allow a rich mixture of grasses and “weeds” (and I use that word in its most non-pejorative sense possible!), there are times of abundant flowering (of dandelions, violets, clovers, and many other breathtakingly beautiful “weeds”) when bees and other pollinators might be out in the lawn. So the question is: is a mowing a recognized hazard for bees?

I poked around in the literature trying to find any studies that examined or quantified the impact of lawn mowing on bees. I could not find a single article. I did find, though, some recent, very comprehensive studies and compilation papers that described the collective matrix of stresses that are negatively impacting bees.  The figure below summarizes the 2013 findings of the OPERA Research Center of the Universita Cattolica del Sacro Cuore in association with the European Union:

bee impacts good versionLawn maintenance practices that generate small field sizes, monocultures of grasses, or that involve the utilization of broadly applied pesticides would definitely fit into the bee stress/impact matrix, but negative impacts of grass mowing practices don’t ever come up in the scientific discussion.

What do I do when mowing my mixed field of grasses and “weeds?” When the clover blooms I just don’t mow. I skip a week or two to let the bees have their fill of the clover nectar and pollen. The yard, the bees, the clover and the mower (me) are all benefited by a week or so off (there are many other things to do in the summer instead of mowing grass)! When I do mow and there are bees out and about on the scattered, flowering weeds, I go slow enough so that the bees (who are exquisitely sensitive to sounds, vibrations, and even electrical fields (see discussion below)) can get out of the way. I also keep my mowing blade quite high and often don’t even cut the clover flowers as I pass through the grass.

Photo Public Domain, Pixabay

Photo Public Domain, Pixabay

In summer the “field bees” that are out gathering pollen and nectar have very short life spans. Worker bees only live for about six weeks spending just the last half of their lives flying out of the hive to visit flowers. During the long weeks of the summer, then, there will be wave after wave of field bees heading out to find flower sources. On their flights they are exposed to potential predators, to sudden changes in environmental conditions, and to other physical dangers (including mowing). Fortunately, the robust reproduction of a healthy hive can keep the field bees coming!

So the answer to my friend concerned about lawn mowing and bees is: the overall impact is probably small and there are some simple things that the mower can do to reduce that impact even more.

There have been several other articles about bees over the past few months. A study by the United Nations’ Intergovernmental Science-Policy Platform on Biodiversity and Ecosystems Services published online back in March enumerated the potential economic cost of the worldwide decline in pollinators. This study stated that both vertebrate and invertebrate pollinators are needed for 35% of the global crop production that sustain human consumers. The value of these crops is estimated to be $577 billion per year, and many of these pollinating species (including birds, bats, and 20,000 species of bees) are facing significant population declines and even extinction.  Causes of these declines include the loss of wild plants and their essential nectar and pollen foods, exposure of of the pollinators to pesticides, and the rising levels and increasingly rapid word-wide distribution of pathogens and parasites. The OPERA study chart (above) summarizes the UN’s findings on pollinator stresses very well.

A team of researchers at Penn State just published a paper in the journal Atmospheric Environment describing the impact of air pollution on the the ability of honeybees to detect (and follow) scent molecules being generated by flowering plants. Rising levels of ozone greatly inhibited the chemical sensory systems of honeybees and led to longer, less efficient foraging and pollinating patterns!

Photo by B. Moisset, Wikimedia Commons

Photo by B. Moisset, Wikimedia Commons

In some happier research, a study published in June in the American Midland Naturalist examined the pollen types gathered by mason bees (Osmia species) around the Rocky Mountain Biological Laboratory in Colorado. A number of the mason bees studied specialized in gathering sunflower pollen from their surrounding vegetative habitats. Sunflower pollen, though, is very low in nutrient quality compared to other types of available pollen. The mason bees, though, that gathered the sunflower pollen had much lower levels of parasitic wasps affecting their larvae. There was a distinct, overall survival benefit, then, of reduced parasitism when the nutrient poor pollen was used nearly exclusively to fill the brood chambers and feed the mason bee larvae! Looking at bumblebees, though, another Penn State research group just published a paper in the Proceedings of the National Academy of Sciences in which they determined that these types of bees preferentially gather the highest nutritional quality of pollen from the flowering species in their habitats.

Photo by Trounce, Wikimedia Commons

Photo by Trounce, Wikimedia Commons

And finally, a study published at the end of May also in the Proceedings of the National Academy of Sciences demonstrated that bumblebees have specialized body hairs that sense electric fields! This type of an electrical sensory system is quite uncommon in terrestrial organisms, but may be used by bumblebees to find flowers or to avoid dangers (like lawn mowers perhaps?). The researchers also speculated that these electrical sensory hairs may be present on many type of insects and may explain some anecdotal observations of insect (especially pollinating insect!) disruptions in areas of human generated “electric smog” (i.e. locations with power lines, and dense concentrations of radio waves and wireless communication networks).

So, your cell phone may be affecting your honey bees, everyone! Keep your calls short!

Summer is racing past! I hope that everyone is out enjoying it!

 

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Signs of Summer 5: Jellyfish

Photo by R. Rezabek

Photo by R. Rezabek

Halifax Harbor (according to many (but not all) authorities) is the second largest natural harbor in the world. It is a beautiful place with lots of history and activity. We visited Halifax on the sixth day of our cruise, and Deborah and I had a wonderful time walking along the harbor boardwalk and looking at the boats and at the people. The photograph to the left was taken by my cousin, Randy Rezabek (who along with his wife, Charlene, was also on the cruise).  It shows a French Navy training sailing ship that had just been sailed across the Atlantic. We watched the crew go about their morning maintenance work on the ship. Then after a pause for a leisurely, group smoke, they all went for a long run down and around the harbor walkway. Only the French would warm up for a five K run by smoking a couple of cigarettes!

There was a nice crowd on the boardwalk and a number of friendly dogs to say hello to and pet. As I mentioned last week, though, there were no seagulls to speak of and the water of the harbor seemed unnaturally still and quiet. I later learned about Nova the hired Harris’s hawk (whom I mentioned last week). Nova served as a local gull assassin and deterrent, but he was not out and about as we walked around the harbor.

Photo by D. Sillman

Photo by D. Sillman

We did get to see something wonderful, though. Standing out on an extension of the boardwalk next to an art display of “melted” street lamps (you had to be there to appreciate it!), we looked down into the water and saw a large, reddish jellyfish (its “bell” was over a foot in diameter) go bobbling by (photo to the left).

There are four common jellyfish in Nova Scotia: the Arctic red jellyfish, the lion’s mane jellyfish, the constricted jellyfish, and the sea gooseberry. It is likely that the Arctic red and the lion’s mane jellyfish are the same species (the taxonomy of their genus (Cyanea) is very confused). So, seeing the size and the red color of this specimen led me quickly to assume it was a lion’s mane jellyfish (an organism that I have talked about in my introductory biology class for many years (more on that later!), but one that I had never seen before in the wild!).

Deborah and I watched the jellyfish for fifteen or twenty minutes (until it disappeared in the ripples and surface glare of the harbor water). No one else seemed to notice it floating by!

Cabbagehead jellyfish, Photo by K. Pepper

Cabbagehead jellyfish, Photo by K. Pepper

Jellyfish are among the oldest multicellular animals in nature. They have been found in fossils that date back almost seven hundred million years! “True” jellyfish (like the beauty we watched floating across Halifax Harbor) are members of the cnidarian class Scyphozoa. They are especially abundant in cold ocean habitats but can be found all over the world. During my high school years in Houston I spent as much time as possible down in Galveston Bay and along the Gulf coast. I remember seeing a particular jellyfish that we called a “cabbage head” (scientific name Stomolophus meleagris) rising and falling in the warm, sheltered waters of the bay. In places the water was densely packed with them! We also frequently had Portuguese Man-o-wars (Physalia physalis) wash up onto the beaches. The man-o-wars, though, are not true jellyfish. They are colonial assemblages of individuals of cnidarian class Hydrozoa. They still sting, though, and are close enough in form and function to be at least casually called “jellyfish.”

Jellyfish anatomy is very simple. They are made up of two layers of single cell thick tissues (one on the outside of the body and one lining the inside). In between these layers (and making up most of their body weight) is a non-cellular mass of gelled water called the “mesoglea.” The two tissue layers have specialized groups of cells that take on sensory functions, nerve-like functions, muscle-like functions, and digestive functions. They also have, especially concentrated on their dangling tentacles, cells called “cnidocytes” that can eject venom-ladened proteins called nematocysts that the jellyfish can use for hunting or for protection.

Lion's mane jellyfish, Photo by D. Hershman, Wikimedia Commons

Lion’s mane jellyfish, Photo by D. Hershman, Wikimedia Commons

The lion’s mane jellyfish (Cyanea capillata) is especially abundant in the cold waters of the North Atlantic and the North Pacific Oceans. It feeds on zooplankton, small fish, and smaller jellyfish. It in turn is preyed on by sea birds, large fish, and sea turtles (the leatherback sea turtle in eastern Canadian waters avidly feeds on lion’s mane jellyfish!). The lion’s mane jellyfish itself is also a very important hiding place for shrimp and many small species of fish. These vertebrate and invertebrate species live among the tentacles of the jellyfish and gain a significant degree of protection from other potential predators.

As I mentioned before, I have talked about Cyanea for many years in my introductory biology course at Penn State. I used it as a vivid example of Class Scyphozoa primarily because of its other common name: the giant jellyfish! In 1870 a specimen of Cynaea washed up on the shore of Massachusetts’s Bay that had a bell that was seven and a half feet in diameter and tentacles that were over one hundred and twenty feet long!   “Giant” is a very appropriate adjective for this species, indeed! I don’t know how long it took that specimen to grow to that size, or if there are other Cyanea of equal sizes out in their cold ocean habitats, but the growth potential of the “one footer” we saw in Halifax Harbor could be impressive!

There is evidence that jellyfish populations all around the world are increasing. Possibly over fishing has reduced jellyfish predator levels or human generated pollution (especially nutrient runoff into the oceans from agricultural fields) has generated conditions increasingly favorable to jellyfish growth and reproduction. Jellyfish, for example, thrive in nutrient-rich ocean waters that are low in oxygen, conditions that are being observed throughout our human-impacted ocean habitats. The large “blooms” of jellyfish can have serious economic impacts. Shoreline power plants have had their cooling water intakes clogged by excessively abundant jellyfish. Some plants have even had to shut power production until the jellyfish numbers could be reduced.

Dried jellyfish, Photo by Oleg, Flickr

Dried jellyfish, Photo by Oleg, Flickr

Amazingly, jellyfish are being actively fished for and processed as human food and are considered to be great delicacies in some Chinese, Japanese, and Korean cuisines! Some shrimp trawlers on the East and Gulf Coasts of North America can actually make more money trawling for jellyfish (especially that “cabbage head” jellyfish (also called the “cannonball jellyfish”) that I mentioned before!

I didn’t talk about jellyfish stings or the wild array of “cures” and treatments for the skin lesions caused by the venom in the nematocysts. I’ll save that for another blog! Just watch your step when you walk barefoot on the beach!

 

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Signs of Summer 4: The Curious Case of the Missing Gulls

MS Vandeem (Photo by D. Sillman)

MS Vandeem (Photo by D. Sillman)

From Arthur Conan Doyle’s Sherlock Holmes story “Silver Blaze:”

Gregory (Scotland Yard detective): “Is there any other point to which you would wish to draw my attention?”

Holmes: “To the curious incident of the dog in the night-time.”

Gregory: “The dog did nothing in the night-time.”

Holmes: “That was the curious incident.”

Halifax Harbor (Photo by D. Sillman)

Halifax Harbor (Photo by D. Sillman)

From the deck of the MS Vandeem cruising down the St. Lawrence River:

Fellow Cruiser: “Is there any other point to which you would wish to draw my attention?”

Me: “To the curious incident of the sea gulls.”

Fellow Cruiser: “But there are no sea gulls.”

Me: “That is the curious incident.”

In anticipating our cruise down the St. Lawrence I prepared myself for two ecological experiences: 1. I anticipated seeing great flocks of sea birds (especially sea gulls) all along the river and estuary, and 2. I anticipated seeing whales (13 species of whales (from belugas to blue whales) spend their springs and summers in the St. Lawrence River and Gulf!). Amazingly, though, there were almost no seagulls or other sea birds to be seen over the week of the cruise, and the only whale we observed was a harbor dolphin that Deborah spotted in Bar Harbor, Maine! The whales might have been avoiding the noise and fuss of our large cruise ship (The MS Vandeem), but sea gulls, based on my experiences along the Texas Gulf Coast and the Virginia mid-Atlantic coasts, should have been drawn to this boat and to the various port towns we stopped at like flies to a picnic!

Where were they?

Ring billed gull, Photo by D. Daniels Wikimedia Commons

Ring billed gull (Photo by D. Daniels Wikimedia Commons)

Background reading about the birds of eastern Canada listed four main sea gull species: the ring-billed gull (Larus delawarensis), the herring gull (L. argentatus), the great black-backed gull (L. marinus) and the black-legged kittiwake (Rissa tridactyla).  The great black-backed gull and the black-legged kittiwake are most frequently found to the north and to the seaward sides of the places we were scheduled to visit (they are true seas dwelling gulls, not, as my cousin Amy recently pointed out to me, bay dwelling “bagels!” (Happy retirement, Amy!)), so my expectation was that we would see quite a few ring-billed gulls (they were estimated to make up 80% of the gulls along the St. Lawrence) and herring gulls (estimated to make up 10% of the St. Lawrence gulls). In fact, the largest single breeding colony of ring-billed gulls was quite close to where we boarded the Vandeem just east of Montreal (on the Ile Deslauriers: a colony of 51,000 pairs of birds!). Unfortunately, we could not see this island from the deck of our boat!  We did see several great blue herons (Ardea herodias) flying over Montreal and down the St, Lawrence just before we boarded the Vandeem, but not many other birds at all!

Herring gull Photo by D. Daniels, Wikimedia Commons

Herring gull Photo by D. Daniels, Wikimedia Commons

Along the Quebec stretch of the St. Lawrence we saw a handful of herring gulls but no ring-billed gulls. When we docked at Quebec City, there were no waiting flocks of gulls of any kind to greet us as we disembarked from the boat. As we continued down the St. Lawrence from Quebec City and headed out into the Gulf of the St. Lawrence, we saw a few more herring gulls, a couple of ring-billed gulls, and a pair of common terns (Sterna hirundo). When we docked at Charlottetown, Prince Edward Island (or Sydney or Halifax, Nova Scotia) there were also no flocks of gulls, no great flying commotion greeting us on the docks.

In Charlottetown we sat out on a dockside table and had several baskets of steamed mussels and clams (and a very fine local ale). We watched two double crested cormorants (Phalacrocorax auritus) stand to dry themselves out on some old pilings in the harbor but were neither entertained nor pestered by any gulls. We had a similar experience on the waterfront boardwalk in Halifax (in Sydney it was far too cold and wet to sit outside! We did see, though, a pair of American black ducks (Anas rubripes) swimming around in a little cove near the dock).

Where were the sea gulls?

Herring gulls have been having a very tough time of it over the past fifty years. The Cornell Laboratory of Ornithology reports that their population has decline 3.5% each year since 1966. That percentage has compounded into an 83% total population decline over this time period! Changes in commercial fishing methods (less dumping of waste fish and refuse), a significant decline in total commercial fishing due to depleted fish populations, and greater control over landside waste disposal, waste dumps and landfills have all reduced the available food for this active, omnivorous scavenger. Further, oil and pesticide pollution and the loss of nesting sites have all had negative impacts on herring gulls. Also, herring gulls incubate their eggs in their huge nesting colonies for over a month, and their nestlings don’t fledge until they are six weeks old! This extended period of egg and nestling existence makes the herring gull quite vulnerable to nest predators (a list that even includes their fellow herring gulls!) and to deliberate human destruction of eggs!

There was an article in The Guardian (June 30, 2010) asking the question, “Why were there no seagulls in Charlottetown. PEI?” One answer came from a reader who reported that a friend of theirs had worked for the Royal Society for the Preservation of Birds (RSPB) back in the 1960’s systematically destroying seagull eggs in nearby PEI colonies (seagulls, according to the RSPB, needed to be destroyed because of their habits of eating the eggs and nestlings of other bird species!).

Harris's hawk (Photo by C. Delgada, Wikimedia Commons)

Harris’s hawk (Photo by C. Delgada, Wikimedia Commons)

Another article I found was published in 2014 on the CBC News web site. This article featured a Harris’s hawk named “Nova” that was hired (along with his handler) by the city of Halifax to patrol the harbor area of the city. The hawk actively killed seagulls and generated a predator presence that greatly reduced the local seagull population!

Deliberate human actions, then, seem to have been one factor in reducing the local presence of seagulls especially in places that wanted outdoor restaurants and harbor-side walkways for tourists (i.e. all of the places that the MS Vandeem took its travelers!).

Another factor that might have been impacting the number of sea gulls that we observed, though, might simply have been the timing of our visit. Both the herring gull and the ring-billed gull were right in the middle of their seasonal nesting periods. Possibly their colonies have been driven far enough away from the high human-use sites of our cruise ship itinerary that the birds were not able to make forays into these towns while still protecting their nests or feeding their nestlings. I like to think that in August the sea gull numbers in this visitation sites would improve. I would be happy to wear a broad-billed hat (and even put a cover over my glass of ale or basket of shellfish) when sitting out at a dockside table if it would mean an accompanying show and clatter of gulls!

 

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Signs of Summer 3: Stink Bugs!

Photo by D. Sillman

Photo by D. Sillman

As we have talked about before, the brown, marmorated stink bug (scientific name: Halyomorpha halys) is a native species of northeast Asia (Japan, Korea, and China) and has become over the past 20 years a serious invasive pest throughout the United States. It is thought that this insect was first released into the United States in Allentown, PA in 1996. It apparently traveled from northeast Asia in a shipping container that was delivered either to the port of Philadelphia or Elizabeth, New Jersey and then trucked to Allentown. Five years later this new, alien, invasive species was recognized and identified by entomologists at Cornell University, but by then large populations were being observed throughout eastern Pennsylvania, New Jersey and New York. This insect has now spread to forty states and is especially abundant in the eastern United States. It has very large populations in Pennsylvania, Maryland, Virginia, New York, New Jersey, Massachusetts, Delaware, Ohio, and North and South Carolina. Its spread to California and Oregon was allegedly via a car driven by a person traveling from Pennsylvania to California in 2005!

The ability of these stink bugs to overwinter is remarkable. There is some mortality among the hibernating bugs, but a significant percentage of them make it through to spring and to their opportunity to mate. A mated female is then able to lay up to three hundred eggs! The relative severity of the winter does, however, affect their percentage of survival. Several models of climate change and global warming have included increased survival of stink bugs at higher and higher latitudinal locations with, then, significantly larger spring and summer populations of this potentially destructive pest. Many of these stink bugs find their way into our houses and spend the winter months hibernating in tiny crevices and hideouts all around us. Their periodic emergence throughout the winter is our only reminder that they are close by!

Brown marmorated stink bugs feed on over one hundred and fifty plant species including a number of crops that are of great economic importance to humans. Fruit trees (especially apple and pear), soybeans, and peanuts are crops significantly damaged by these insects. I have also seen stink bugs in my yard feeding avidly on the grapes growing on my grape vine.

D. Lance Wikimedia Commons

D. Lance Wikimedia Commons

When these stink bugs first made their appearance here in Western Pennsylvania most potential predators were actively repelled by their pungent scent. Spiders, birds and almost every other type of possible insect eating invertebrate and vertebrate species actively avoided contact with the stink bugs, and, subsequently, their populations grew out of control. In the fall of 2013 and in the spring of 2014 we caught thousands of stink bugs in and around our house. We filled up dozens of one liter, plastic bottles with their carcasses! Over the past two years, though, we have not experienced these huge fall and spring outbreaks! This spring I have caught maybe twenty or thirty total stink bugs (I haven’t even filled one plastic bottle yet!). A far cry from the thousands of 2013 and 2014!

Photo by D. Sillman

Photo by D. Sillman

What has happened? It may be that predators are adapting to the noxious scents of the stunk bugs and are reducing their effective populations! We have observed spiders actively trapping and eating them. The picture Deborah took of this jumping spider chewing its way into the captured sink bug is a great visual of arthropod control! Birds (especially titmice and chickadees) regularly flare up to the window screens of my house and snag unwary stink bugs. They fly them over to nearby branches and gobble them down! (Go chickadees!)The predator guilds of our surrounding vertebrate and invertebrate communities have apparently adapted themselves to this new (and formerly incredibly abundant) food source! Control has been achieved, at least in the area immediately around my house!

A few months ago an old friend, Karen Shaver, sent me a link to an article about predators of brown marmorated stink bug eggs. The article (published in the journal Biological Control) was written by Rob Morrison (a research scientist at the USDA-ARS Appalachian Fruit Research Station in Kearneysville, WV). Morrison and his colleagues tested twenty-five potential arthropod predators of stink bug eggs and found several that voraciously devoured the egg masses. Katydids, crickets, ground beetles, jumping spiders and earwigs all actively ate the stink bug eggs (it is especially nice for me to see earwigs talked about in a positive manner! (See my essay about earwigs in my July 23, 2014 Signs of Summer #7 blog!)). Morrison’s group emphasized that modifying habitats to encourage the growth and abundance of these egg predators might be a very effective, long term way to control the populations of this potentially destructive crop pest!

So the brown marmorated stink bug is still with us, but it seems to be getting under control mostly through ecosystem adaptations to its presence and to its potential as prey and food for both vertebrate and invertebrate predators! Pesticides have not been terribly effective in preventing crop damage by stink bugs primarily because of their mobility (they hide in vegetation away from the treated field crops and then swoop in to feed thus limiting their exposure to the applied pesticides). The new observations of active predation of adult bugs and their eggs by an array of arthropod species might indicate that non-targeted destruction of crop dwelling arthropod predators via the pesticide treatments might actually make the stink bug infestation worse!

So, stink bugs are a relatively new and not terribly pleasant sign of summer for Western Pennsylvania. Fortunately, our surrounding biotic community is hard at work to keep them from being the ONLY sign of summer and fall that we notice!

 

 

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Signs of Summer 2: Ticks and Lyme Disease

Photo by D. Sillman

Photo by D. Sillman

Last June I wrote an article about ticks and Lyme disease, too. It has, unfortunately, become one of our important, although depressing, signs of both spring and summer. My dog, Izzy, had a tick last January (during one of the warm spells of our strange winter!) and just got another one a couple of days ago. After a short winter break, the ticks are back!

Pennsylvania is experiencing a population explosion in black-legged ticks (the tick formerly called the “deer tick” but most precisely known as Ixodes scapularis). This tick is small and quite common, and it is found throughout the northeastern and north-central parts of the United States. The reason for its observed increase is not precisely known. Some interesting explanatory hypotheses include the exploding populations of rodents (especially white-footed mice) particularly in our suburban ecosystems.  Fragmentation of forests and the optimal conditions of suburban habitats 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 very likely to find a white-footed mouse on which to feed. These mice are also significant reservoirs for the bacterium that causes Lyme disease, so the ticks that get their blood meal from them have a very high probability of assimilating and then passing on these bacteria.

A second hypothesis that tries to explain the increases in ticks suggests that the observed increase and apparent spread of these ticks involves their return to habitats from which they had been previously extirpated. Tom Simmons of Indiana University of Pennsylvania speculates that Pennsylvania’s forests were once loaded with black legged ticks. Clearing of these forests (95% of Pennsylvania’s forests, as we have talked about previously, were cut sometimes repeatedly since European settlement) and the destruction of the native deer populations (a favorite host of the adult stages of the black legged tick) forced these ticks into greatly restricted habitats from which, as both forest cover and deer populations have recovered, they are now emerging.

Photo by California department of Public Health (Flickr)

Photo by California department of Public Health (Flickr)

Possibly both hypotheses (along with some that haven’t even yet been articulated) are leading to the explosion and spread of both the black legged tick and its symbiotic, Lyme disease causing bacterium (Borrelia burgdoferi). For the last several years, Pennsylvania has led the nation in the number of human cases of Lyme disease (in 2014 there were 7487 conformed human Lyme disease cases in Pennsylvania up from 5904 cases in 2013. I have not been able to find either Pennsylvania or national Lyme disease data for 2015, but I have a feeling that the numbers have increased again!) Further, the Center for Disease Control (CDC) state that the number of reported Lyme cases in the United States (30,000 in 2014) was only 10% of the total number of cases. A lot of people are experiencing Lyme disease!

Let’s go back through the black legged tick’s life cycle:

Eggs deposited in the fall in low, grassy or scrubby vegetation hatch the next summer into the very small, six-legged larva life forms. These tiny ticks typically seek out small hosts (like a white-footed mouse or a bird) but are able opportunistically to attach to larger mammals 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 often is 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 the spring (May and June here in Western Pennsylvania) is a time of great risk for ticks bites (and disease transmission) for humans!

Photo by D. Sillman

Photo by D. Sillman

After the nymphs have taken their blood meals they molt into adults. These adults are especially abundant in the fall. These much larger ticks (like the one in the picture to the left) typically attach to large mammals like white-tailed deer. The female adult ticks take a large 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.

The Pennsylvania Department of Environmental Protection collected and tested black-legged ticks and determined that 34% of them carried Borrelia burgdoferi. It is not known if this is an increase from previous years or not, but these data will provide a comparison baseline for future tick assessments.

A few things to remember about ticks and Lyme disease: black-legged ticks are not able to begin blood feeding (and consequential pathogen transfers) until they have been attached to a host for at least 36 hours. Careful examination for ticks and their rapid removal is the best way to prevent contracting the Borrelia bacterium. Preventing tick attachment is an even better strategy to avoid Lyme disease. Also, ticks don’t drop out of trees onto you, they attach to your legs or arms when you brush against vegetation on which the tick is waiting. So, wear long pants and long-sleeved shirts when out in the woods or fields, use DEET-based insect repellents on socks, pant legs, etc. A thorough “tick check” after being out in a potential tick habitat is also a very effective way to reduce the chance of infection.

Careful examination for ticks and their rapid removal is the best way to prevent contracting the Borrelia bacterium. Tick removal is best accomplished using a pair of forceps or a v-slotted, commercial “tick-remover.” Gently pull the tick from its spot of attachment making sure that you remove the feeding structures (the “head”) along with the body. Then dispose of tick in whatever creative way you might wish!

Photo by D. Sillman

Photo by D. Sillman

If you do happen to miss an attached tick you have about a 2% chance of having the Lyme disease bacterium transferred to your blood stream. A few days after a tick bite most people will experience a red bump at the site of the wound. If the tick has transmitted the Lyme bacterium typically (70 to 80%% of the time) the localized redness of the wound will expand over 3 to 10 days into a 5 cm (or more) diameter circular rash. In some individuals the pattern of the redness takes on a “bull’s eye” configuration, but it can just as easily simply be a large red circle. Early Lyme disease can then develop in 1 to 4 weeks in the form of a flu-like illness with fever, fatigue and body aches. If you have been out where you might have encountered a black legged tick and have then observed the red spot expanding into red circle (whether or not the fever syndrome has developed), this is the time to contact your doctor! Antibiotics are extremely effective at this point in preventing the development of most of the serious side effects of Lyme infections!

Untreated Lyme disease can lead to neurological problems, joint pain and a cluster of other, fortunately, uncommon symptoms. “Post-treatment Lyme Disease Syndrome” (PTLSD) (sometimes referred to as “chronic Lyme’s disease) is a very serious but also very preventable condition. Johns Hopkins Medical Center emphasizes that early antibiotic treatment (within 72 hours of a tick bite) with a single 200 mg dose of doxycycline can prevent the development of Lyme disease. If treatment is delayed and Lyme symptoms develop, then longer durations of antibiotic treatment are required. (for more information about Lyme disease I recommend checking out the John Hopkins Lyme Disease Clinical Research Center.

Dogs can also develop Lyme disease. Most dogs (95%) that receive the Borrelia bacterium via a tick bite actually show no symptoms at all. Those dogs that do react to the bacterial infection often develop lameness in one of their legs that typically lasts for a few days. The lameness can then shift to another leg and can be quite debilitating. In some dogs the Lyme infection can also lead to kidney disease and even kidney failure.

The number of dogs who get Lyme disease each year is not known. There is no centralized reporting system to monitor this disease. Anecdotally, I can report that my local vet, a small mostly rural practice, saw well over 100 Lyme disease cases last spring and summer! If every vet is seeing similar numbers, there is truly an epidemic of Lyme affecting our dogs!

Photo by D. Sillman

Photo by D. Sillman

Cats can also be hosts for black legged ticks and have, therefore, the potential to encounter the Lyme bacterium. The Cornell University College of Veterinary Medicine, though, emphatically states that cats are not able to get Lyme disease from tick bites. The bacterium is either not able to be transferred from tick to cat during a blood meal or the transferred bacterium is not able to survive and replicate in the cat.

Welcome to summer, everyone: days of sun and warmth (and mosquitoes and ticks)! We have the very good along with the bad!

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Signs of Summer 1: Spider the Turtle

Photo by D. Sillman

Photo by D. Sillman

My daughter, Marian, got her eastern box turtle from a pet store back in 1998. The store owner said that the turtle (soon to be named “Spider” by my daughter) had been a pet but that the previous owner no longer could take care of him and, so, had brought him to the store so that he could find a home. We didn’t know how old Spider was, but he had all of the features of a mature, adult box turtle (a high domed carapace (upper shell) and a hinged plastron (lower shell) that could tightly close both his head and tail openings. We knew he was a male because of his bright red eyes. Spider easily could have twenty years old (or more) in 1998, and he lived with us for the next eighteen years. When Marian went off to college in 2004, I took over Spider’s care and maintenance.

Spider was an important harbinger of Spring (his early March breaking of his winter-long fast was big news on this ecology blog!) and also of Fall and Winter (his settling into his November torpor in his terrarium foreshadowed the coming cold gray days of winter). He loved to sit in his large water dish often with his head under the water for very long periods of time, and he loved to eat nightcrawlers! He was very adapted to living in a terrarium (he thought food came from the sky and, if hungry, would stretch his neck out and stare straight up (waiting for his earthworms or pieces of fruit to be delivered). I am very sorry to report that Spider passed away yesterday. He never really came out of his winter torpor this year and would not eat (not even very fresh nightcrawlers!). He lasted two months past his usual waking up time but was obviously fading away. Below, in honor of Spider, is the discussion about box turtles from the Virtual Nature Trail.

The eastern box turtle is a familiar and easily recognized inhabitant of the Nature Trail ecosystem. Box turtles are long lived animals that are relatively slow in reproducing. They reach sexual maturity only after four or five (or possibly twenty!) years of life, produce relatively small numbers of eggs, and have a high hatchling mortality rate. Their numbers in the wild have, unfortunately, been steadily declining primarily due to habitat destruction. It is hoped that protected habitats like the Nature Trail and increased awareness by the general public will be sufficient to allow this species to maintain itself as a viable component of our Western Pennsylvanian ecosystems.

Photo by D. Sillman

Photo by D. Sillman

The eastern box turtle is small (4.5 to 6 inches shell width, up to eight inch shell length), land turtle with a high, dome-like upper shell (“carapace”). Younger box turtles can be distinguished by their flatter carapaces. The carapace can have quite a variety of colors and patterns ranging from a smooth, highly camouflaged, green to a brightly marked, brownish black with yellow and orange highlights. The patterns of the markings on the carapaces of box turtles are often distinctive enough to allow identification of specific individuals within a population. The carapace also typically has a ridge (the “keel”) down its centerline and flared edges (the “marginals”).

The head and neck and legs of the eastern box turtle are also heavily patterned with distinctive yellow to orange and, occasionally, reddish streaks. Their under shells (the “plastrons”) range in color from yellow-brown to brownish-black and are hinged to allow movement of the anterior and posterior sections. A box turtle is able to use these hinged plastron lobes to tightly close its head and tail openings. The fit of the closed hinged plastron against the carapace is so tight that not even the blade of a knife can be inserted between them. This ability to tightly encase their bodies within their shells provides the eastern box turtle with a very effective mechanism of defense. Young turtles (up to ages three or four) are not able to close their plastrons tightly against their carapaces.

It is quite easy to determine the sex of an eastern box turtle. Males have concave plastrons, thicker based and longer tails, longer front claws, and bright red or orange eyes. Females have flat or slightly convex plastrons, short, thin tails, and dark red or brown eyes. Also, the “vent” opening (the common, “cloacal” opening of the lower digestive, urinary and reproductive tracts) in the male is typically found past the margin of the carapace while in the female it is located under the carapace edge.

Photo by D. Sillman

Photo by D. Sillman

Eastern box turtles live thirty to forty years in the wild and have been alleged to reach ages of one hundred years or more in captivity.  A box turtle grows very rapidly for the first four or five years of its life reaching sexual maturity in four years but full adult size only by age twenty. Some have stated that only fully grown box turtles, in spite of apparent earlier sexual maturity, are actually reproductively active.

Eastern box turtles are found from New Hampshire to Georgia, and west to Michigan, Illinois and Tennessee. They prefer open woodlands, pastures, and marshy meadows. They are most likely to be found in moist habitats and spend a great deal of their time buried in the leaves and surface soils and hidden in the brushy piles of their forest habitats. Their optimal environmental temperatures are between 70 and 85 degrees F, but they will tolerate nighttime temperatures down into the 50’s. During the summer, they are seldom active during the mid-day heat and do most of their hunting and foraging during the cool, early morning hours. They often soak themselves in puddles, seeps, springs and other muddy places for hours or days at a time. As temperatures fall in the autumn, eastern box turtles enter into hibernation (usually starting in October or November) and burrow into loose soil, mud, or abandoned mammal burrows. As the soil temperatures drop with the coming winter season, the turtles burrow deeper and deeper into their hibernacula.

Eastern box turtles are predominantly carnivorous during their younger years and become more and more herbivorous as they age. Prey items taken by box turtles include, snails, worms, insects, spiders, frogs, snakes lizards, small mammals, and carrion. They also eat fruits, berries, leaves and many types of mushrooms. Some of the mushrooms consumed by box turtles are very toxic for humans, so it is inferred that the turtles are unaffected by these potential poisons. Humans eating box turtles that have recently fed on poisonous mushrooms may become quite ill due the toxins that have accumulated in the turtles’ flesh.

Photo by D. Sillman

Photo by D. Sillman

Turtles will forage over an area the equivalent of two football fields over their lives. Adult individuals occupy “home ranges” of variable sizes (larger in less favorable habitats or in systems with relatively low population densities, smaller in more favorable or more densely populated habitats). Immature individuals (less than nine years of age) and many mature, but un-established males move extensively about as “transients.” The directionality of their movements is, apparently, “one way,” and quite energetically directional! (So, if you rescue a box turtle crossing a road ALWAYS put it over on the side to which it was heading!).

Box turtles are often found near to each other and can form range-overlapping, socially tolerant groups of three or four individuals. Fighting and other types of aggressive behavior are rare with the exception of occasional “sparring” matches (especially between completing males) that involve alternative bouts of two individuals biting each other’s shells with, obviously, little damage to either individual. Eastern box turtles walk with a steady, energetic stride holding their heads upright. They can travel 50 yards or more in a single day and strong homing instincts that compel them to move in the direction of their home ranges.   

Photo by D. Sillman

Photo by D. Sillman

Female box turtles are callable of storing sperm in their oviducts for up to four years and are thus able to produce viable eggs for many years following a single mating. They will mate between May and October. Eggs are laid into flask-shaped holes that are three to four inches deep. The holes are meticulously dug by the female into the soil of sunny, warm sites. Three to six elliptical, leathery eggs are laid and then covered to incubate and then hatch on their own. Several clutches can be laid per year. Incubation lasts two to three months. A clutch that hatches late in the season may over-winter in the nest hole and emerge the following spring.  

This will be my first summer in eighteen years without a turtle to play with and watch and feed. Spider will be missed!

 

 

 

 

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Signs of Spring 13: Mosquitoes!

D. Sillman

Photo by D. Sillman

As the temperatures start to slowly rise back up into more comfortable ranges, and Signs of Spring give way to Signs of Summer, Deborah’s and my thoughts inevitably turn to pulling out our folding chairs and getting outside in the evening to watch and feel the day come to a close. We usually get most of the month of April and then a good part of May (depending how fast summer really sets in) to enjoy long evenings outside, but by June something comes up that limits our time outside: mosquitoes.

There are always a few mosquitoes right away in the spring, but it takes some time and some continuous warm temperatures for the real swarms to arise. This staged invasion is due to the way that different mosquito species survive the winter.  Our native mosquito species, by the way, don’t seem to be negatively affected by very cold winters or excessively stimulated by very mild winters. They are able to roll with our fluctuating climate and pull themselves back into their reproductive (and blood meal requiring) life stages with great ease and efficiency.

Photo by J. Gathany, CDC Wikimedia Commons

Photo by J. Gathany, CDC Wikimedia Commons

Some of our mosquitoes overwinter as cold resistant eggs while others hibernate as larvae. There are also a few mosquito species that overwinter as mated adult females. These adult females emerge early in the spring and are ready right away for a blood meal so that they can finish making their eggs. They are the first attacking wave in the early spring. Again, cold spring temperatures may delay their emergence, but the cold does not seem to significantly reduce their numbers. So there are a few mosquitoes active as soon as air temperatures get sufficiently warm, but the swarms don’t come until all of those overwintering eggs and larvae mature and begin to seek their blood meals.

There are so many things to say about mosquitoes, and so many different points of view to take about them!

Photo by Abhishek, Wikimedia Commons

Photo by Abhishek, Wikimedia Commons

Dr. Nora Besansky is a biologist at Notre Dame University who specializes in mosquitoes. She was interviewed on NPR back in February and spent most of her on-air time emphasizing how beneficial and important most mosquitoes are. Of the four thousand or so species of mosquitoes less than one hundred actually transmit human diseases. The rest occupy important places in many food chains (for mammals, birds, fish, amphibians, reptiles, and wide range of insects and other arthropods) and also function as pollinators for many species of plants (all adult mosquitoes, Dr. Besansky emphasized, drink flower nectar). Blood feeding by mosquitoes is only carried out by females and is needed to provide the protein and iron required to make viable eggs. The female mosquitoes can take a blood meal from a wide variety of potential hosts. The list of possible hosts, in fact, is nearly identical to the list of what can eat mosquitoes, and different mosquito species specialize on particular types of hosts.

Another perfectly reasonable point of view, though, concerning mosquitoes looks at the nearly one hundred mosquito species that can transmit diseases to and in between people. There are some serious diseases on the mosquito transmitted list! Malaria, yellow fever, Dengue fever, West Nile virus, and a whole slew of encephalitis syndromes are all carried by mosquitoes.  Over the past winter, our awareness of a new mosquito borne virus spreading across South and Central America, the Zika virus, has triggered intense discussions about mosquito control procedure and the safety of travel to Zika affected areas. Each year, according to EB Medicine (an on-line medical reference site), seven hundred million people get a mosquito transmitted illness. Most of these cases occur in human populations residing in tropical and subtropical climate zones, and about half of all of these cases involve malaria.

So here in Western Pennsylvania (which for now anyway, is about as non-tropical or subtropical as you can get!), we have nothing to worry about, right? (I bet everyone reading this can feel the coming bad news that is about to extend this essay!).

Anopheles (Photo by J. Gathany CDC Wikimedia Commons

Anopheles (Photo by J. Gathany CDC Wikimedia Commons

Let’s talk about the mosquitoes that spread some of these diseases: Malaria is caused by a protozoan parasite called Plasmodium. Plasmodium is most commonly spread by mosquitoes of the genus Anopheles. The very good news is that Anopheles mosquitoes, unlike our more robust native mosquito species, cannot survive our long, cold winters and are, therefore, not found in Western Pennsylvania. Fortunately, malaria is not something we have to worry about locally!

Aedes aegypti Photo by J. Gathany CDC Wikimedia Commons

Aedes aegypti Photo by J. Gathany CDC Wikimedia Commons

When we talk about mosquito spread viral diseases, though, like yellow fever, Dengue fever, and Zika, we are especially (but not exclusively) talking about mosquito species that are in the genus Aedes. Aedes aegypti , in particular, is an active, wide-spread tropical and sub-tropical mosquito species and is often the species involved in the transmission of these illnesses to humans. Aedes aegypti has all sorts of specializations that make it very difficult to control. It can lay its eggs in very small pools and puddles of water. Its larvae can develop successfully in the tiniest volume of even the most stagnant water (think rain water collected in a discarded tin can or old tire!), and bacterial growth in these water sources actually stimulates egg development! The adult Aedes mosquitoes are most active at dusk and at dawn especially in shady areas, but they can bite (and spread their viruses) at almost anytime during the day and also at any time of the year. Adults can also live exclusively inside of houses and other buildings often taking their blood meals while the people in these buildings are asleep.

Aedes albopictus Photo by J. Gathany CDC Wikimedia Commons

Aedes albopictus Photo by J. Gathany CDC Wikimedia Commons

So where is the boundary between the temperate and subtropical climate zones? How about 250 miles from here? How about even closer than that? There are established populations of Aedes aegypti  and other Aedes species in Washington, D. C.! There are also periodically occurring populations of Aedes albopictus (the “Asian tiger mosquito”) right here in Western Pennsylvania, and there is some indication that the Asian tiger mosquito is developing a tolerance for our cold winters and may be setting itself up as an established alien species! The Asian tiger mosquito can carry all of those diseases listed above and may represent a significant human health threat!

It is always “good news/bad news” when thinking about these ecological and medical problems. The really good news is that our cold winters limit the ability of these virus and parasite carrying mosquitoes to establish themselves in Western Pennsylvania. The bad news is that these mosquitoes are evolving to get around that limitation and, with the ongoing warming associated with climate change, the climate seems to be meeting the species changes half way! Mosquitoes and ticks, unfortunately, are some of our signs of spring and summer! I will talk about ticks next week in our first “Signs of Summer!”

 

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