Wednesday, May 11, 2016

A Serious Sipedon

Predation, or when one organism eats another, is common a phenomena at the dinner table. Out in the wild though, predation has a mythic quality to it: we know it happens, be we rarely get to see it. Fortunately, I witnessed such an event this past weekend.

While hiking on the boardwalk at a local marsh (as part of a birding competition no less), I couldn't overcome my habit to continually look at the ground. Out of the corner of my eye, I saw a rather perplexing shape. It had the scales and pattern of a snake, but it was big, round, and short. It took me a second to realize that I was looking directly down onto a water snake in the middle of eating a frog.

Upon closer inspection, it was a Northern water snake (Nerodia sipedon "serpent flowing through causing decay", Greek) eating a green frog (Lithobates clamitans "yelling one who haunts a stone", Greek; maybe this predated individual should be re-classified as Lithobates calamitati "misfortunate one who haunts a stone"--etymology joke!). Northern water snakes are active hunters, and they can use both olfactory and visual cues to hunt for prey. They are solid swimmers with physiological adaptations for increased blood oxygen capacity. As a result they can stay submerged in water for over an hour (65 minutes).

The water snake slowly swallows the green frog. The frog is so large,
the snake must unhinge its jaws to swallow the frog whole. Coming back
30 minutes later, you can see the frog is now midway down the snake's body
(bulge near the stick in picture four).

The diet of Norther water snakes is mainly comprised of fish (50-96% of diet by volume, 56-90% of diet by frequency). Most species consumed are rough fish (a term simply meaning that anglers don't care too much for them as sport), and many are consumed as carrion. Amphibians make up the rest of their diet, but they are often eaten less frequently (4-52% of diet by volume, 17% of diet by frequency). Nevertheless, Northern water snakes are a generalist, and they have also been documented to eat shrews, crayfish, leeches, and a whole host of other animals. In the case of our misfortunate green frog above, we don't know where the green frog was actually caught. Northern water snakes can hunt on the water's surface or swim underwater to hunt. As the case is here, prey are usually brought to a shallow area of water to work about in the mouth.

Unfortunately, Nerodia water snakes of all kinds are often confused with cottonmouths (Agkistrodon piscivorus) an aquatic venomous viper. Nerodia actually have no venom, and their first instinct is to escape by swimming or diving. Otherwise, when harassed, they have a vile temper. Just think, it's probably because they could be fishing instead of dealing with you!

All facts come from the Nerodia sipedon species account found in:
Ernst, CH & EM Ernst. 2003. Snakes of the United States and Canada. Smithsonian Books.

Friday, July 10, 2015


With summer well under way, it's the time of year for critters of all sorts to be laying their eggs. Whether bird, reptile, or amphibian, hear are some of the eggs I've come across in the past few weeks.

Killdeer eggs blend in nicely with the gravely areas they make their nests.
Four eggs are in the far right of this picture.

To start off, we have the fine-feathered shorebird, the Killdeer (Charadrius vociferus, "Noisy plover"). This bird doesn't have to be on the coast to be seen, and it is most well-known for its loud and frequent calling. Killdeer are ground-nesting birds, and their eggs are camouflaged for the gravel-like and sandy areas they like to lay. When threatened, a Killdeer guarding its nest will either fluff its feathers and tail to scare animals off, or it will pretend to have a broken wing so as to distract predators from its eggs.

Reptiles have been laying their eggs too. Instead of brooding eggs like birds, reptiles must lay their eggs in substrate that is warm enough to act like a natural incubator. This usually means sunny, dry, sandy areas. This common snapping turtle (Chelydra serpentina, "Snake-like turtle") exhibited an interesting behavior of shuffling her eggs around are depositing them each time. A snapping turtle's clutch can contain between 20-40 eggs.

As you know, I am a big fan of salamanders that breed in vernal pools. The Ambystoma genus of salamanders (Spotted, Jefferson's) laid earlier in April, and their eggs have been hatching over the patch few weeks. Unlike other eggs anywhere else, the eggs of Spotted salamanders have a unique symbiotic relationship with algae. So far, they are the only known vertebrate species that has a symbiotic relationship with algae. These algae, known as Oophila amblystomatis, not only invade the jelly of the egg, but they also invade the embryo and salamander tissue. The salamander benefits from increased oxygen and removal of ammonia waste during development, and the algae benefits excreted nutrients. Much is still not know about this relationship, but is clear that without the algae, eggs develop more slowly, have higher mortality rates, and produce smaller young upon hatching.

Algae covered Spotted Salamander larvae await to hatch at the end of May.

From a few months ago, underwater footage (couldn't help myself)
 of Jefferson's salamander eggs. Notice, they lack the algae their close cousin's have.

Kerney, R. (2011). Symbioses between salamander embryos and green algae. Symbiosis, 54(3), 107–117. 

Sunday, April 5, 2015

So Long, Winter

It is that fun time of the year where one day is sunny and warm and the next day it snows. While the seasons battle it out for spring's inevitable victory, wildlife are beginning to respond to the changing weather. Birds begin their migrations and add some variety to the resident birds that stayed through the winter. Those animals that hibernated or slumbered in their torpor are stirring. Perhaps my favorite of all is that of the vernal-pool breeding amphibians. Vernal, Latin for spring, describes wetlands that usually only exist during the springtime. These wetlands are typically filled by winter precipitation and snow-melt and are dry and gone by the end of the summer. This ephemeral existence means fish can rarely establish themselves, so amphibians can develop without fear of predation by fish. So, as these seasons change, let us say "see you around" to our winter friends and hello to our spring buddies.

For the first time I tried to point my camera trap skyward, and while it didn't stalk the visitors of my bird feeder quite as well as I had hoped, I did catch some decent photos of the avian folks who spent the winter in the woodlot behind my townhouse. I am still a birding novice, but I did count eight species at my bird feeder this year. All of them are familiar faces to those who put up a bird feeder during the winter. Pictured above we have the black-capped chickadee (Poecile atricapillus,  meaning "spotted black-hair"). These common birds have dynamic brains, where they let old brain matter to die off each autumn so that new neurons can be formed to better match changing conditions. 

We also have the white-breasted nuthatch (Sitta carolinensis) exhibiting the characteristic upside-down nuthatch position. As evidenced by this photo, white-breasted nuthatches visit feeders along with other birds. When the tufted titmouse (the other bird in the picture, Baeolophus bicolor, meaning "two colored little crest") is removed from feeding flocks, the white-breasted nuthatch is much more wary of bird feeders, indicating it relies on other birds to help watch for predators when feeding. Other favorites of mine this year were the dark-eyed junco (Junco hyemalis meaning "winter bird"), the house finch (Haemorhous mexicanus, meaning "Mexican fruit biter"), and the mourning dove (Zenaida macroura, meaning "long-tailed daughter of Zeus")

It's also time to welcome our early ectotherms. Here in the northeast, we most notably have the Jefferson's salamander (Ambystoma jeffersonianum) that will begin breeding even when vernal pools have ice covering them. As part of our research on the vernal ponds in the area, we often catch hundreds of Jefferson's salamanders. These salamanders are extremely slimy. The slime they excrete not only deters predators, but it is also thought that they use the slime to communicate chemically with each other. During the mating season, leaving a persistent scent trail may be helpful in courtship. By chance, when checking our traps this season, we found a midland painted turtle (Chrysemys picta marginata) who must of woke up too early!

As you can tell, I recently got access to an underwater camera and am taking full advantage of it. 


Monday, February 2, 2015

Snake, Rattle and Roll Part 2: This Time It's Personal

*Blood Disclaimer: Images from veterinarian surgery below.

A long while ago, I wrote about surveying for timber rattlesnakes (Crotalus horridus) in the Midwest. Last summer I had the opportunity to visit those sites again, although this time it was for a different purpose. Working with a Department of Natural Resource’s contractor, our goal was to survey known rattlesnake populations in an effort to characterize the prevalence and distribution of snake fungal disease (SFD), a recently documented wildlife disease.

Basking amongst the warm rocks. The snake bag was poised and ready!

While scattered reports of the disease have been surfacing over the past several years, SFD is still surrounded by a shroud of mystery. It is currently hypothesized that the fungus Ophidiomyces ophiodiicola (From Greek “ophio” meaning serpent, and “myces” meaning fungus) is the agent of the infection, but the evidence remains unclear. The disposition of a snake does not improve matters. Generally, snakes are solitary creatures, making it difficult to understand how the disease is transmitted. One possibility is transmission during hibernation. In this region timber rattlesnakes have community hibernacula, so the disease may be spread when several individuals come into contact during the winter. Another possibility is that the fungus is ubiquitous throughout the environment and only becomes pathogenic under certain conditions. 

Since long-term population monitoring is rare, and since SFD is so new, it is challenging for scientists to get a clear picture on how SFD is impacting snake populations. Nonetheless, there is compelling evidence that SFD has harmed and will continue to impede snake conservation (Sutherland et al., 2014). Currently, reports of SFD have occurred mainly in the eastern United States. Several snakes species have had reported signs of SFD infection; however, SFD first gained attention due to its impacts on northeastern populations of timber rattlesnakes and eastern massassauga populations in Illinois. Within a single year, SFD played a clear role in the 50% decline of the last New Hampshire population of rattlers in 2006 (Clark et al., 2011). To shed some light on the situation, research is currently being done to understand the disease's dynamics. So, let’s get back to the Midwest!

To avoid being bitten, venomous snakes are 
measured and handled while safely stuck in a tube.

On a sweltering day in June, with the mayfly hatch swarming, we spent the morning hours scouring  prairie hillsides. Whether basking at the edge of cover or hiding under shelf-rock, we found several rattlesnakes during our search. Once we captured them with snake tongs and safely deposited them into a snake bag, we moved to a convenient place to work each individual up (somewhere not at a 45 degree slope!). We determined their weight, length, gender, and body condition. Several snakes looked healthy, but one individual had a conspicuous node on its side. Since SFD causes a variety of skin defects (blisters, lesions, swellings), we took it in to have the node removed and biopsied.

The types of infections caused can SFD can vary greatly, 
from nuisances like this node to severely damaged respiratory tissue.

It was my first time witnessing an animal surgery, and it was enlightening to see a side of wildlife science completely unknown to me. To top it off, I got to play honorary veterinary assistant (don’t worry, the trained individuals did all of the important things). Once the snake was calmly anesthetized, the veterinarian carefully removed the node, gave the tissue to the wildlife ecologist doing work on SFD, and neatly sutured the snake’s wound. A day later, the snake was released back at the point it was captured.

This snake can't avoid being stuck in a tube! Here, it enters the
 apparatus to receive a constant air flow that contains the anesthesia.

Throughout the surgery, the snake's breathing and vitals are closely monitored.
Here the dilated pupils indicate that the snake is nice and relaxed.

I just recently learned the node's biopsy came back positive for O. ophiodiicola, so it was considered to be a SFD infection. At this point some might ask, “why let the potentially infected snake back out into the wild?”. Too little is currently known about SFD to know how to effectively combat it. Most likely, if the disease had already infected that one snake, the fungus was present throughout the whole area. Considering timber rattlesnakes are having a tough time in many parts of their range, removing an individual would be more detrimental than releasing the infected snake--especially since the mortality rate of SFD varies dramatically.

The surgery area is prepped.

Doc said "scalpel", so I handed him a scalpel.  

Here, the node has successfully been removed. The tissue was 
then divided and placed in a vial for further analysis.

To finish the surgery, the wound was stitched closed and it was given fluid to rehydrate.
Once the snake appeared responsive from coming out of the anesthesia, it was placed back
in its transportation container.

It was great to re-visit these timber rattlesnake populations once more. I can only hope the researchers working on this project will not only get a better sense of where SFD occurs but also its underlying cause so that proper disease management can be undertaken. 

If you think you have come into contact with a snake that may be showing signs of SFD, call your state wildlife agency. Also, clean your shoes and any other gear with soap and water. Then soak in a 10% bleach solution.

All surveys were done with appropriate permissions, permits, and humane handling protocols.

Clark, R. W., Marchand, M. N., Clifford, B. J., Stechert, R., & Stephens, S. (2011). Decline of an isolated timber rattlesnake (Crotalus horridus) population: Interactions between climate change, disease, and loss of genetic diversity. Biological Conservation, 144(2), 886–891. doi:10.1016/j.biocon.2010.12.001

Northeast Partners in Amphibian and Reptile Conservation. 2013. Snake Fungal Disease: Frequently Asked Questions.

Sutherland, W. J., Aveling, R., Brooks, T. M., Clout, M., Dicks, L. V., Fellman, L., … Watkinson, A. R. (2014). A horizon scan of global conservation issues for 2014. Trends in Ecology and Evolution, 29(1), 15–22.

USGS National Wildlife Health Center. 2013. Snake Fungal Disease in the United States.

Sunday, September 21, 2014

Bugged by Pollution

One would think that the word "wildlife" would involve all living creatures, but in reality, it traditionally refers to vertebrates. Thankfully, in the past few months, I have had the opportunity to branch out of the traditional realm of the wildlife biologist and have been introduced to the overwhelming world of arthropods. The phylum Arthropoda, meaning "jointed leg", has over one million described species, and it is estimated that there are four to nine million species that have yet to be formally described (Ødegaard 2000). Arthropoda includes many types of animals: crabs (crustaceans), spiders (arachnids), and butterflies (insects).

Today, I am going to focus on three insect orders. These insects are useful in understanding the health and condition of the environment around us--specifically water quality. Water quality directly affects our well being in many ways. For recreation, poor water quality may mean that the local summer swimming spot is closed because of harmful bacteria. High water quality may mean the creek nearby can support healthy fish  for whatever fishing habit we may have. Economically, water quality also impacts the amount of effort it takes for water treatment plants to make our water potable. So, how do we measure and understand water quality?

Fishing Creek, Clinton Co. Pennsylvania.

While there are many techniques one can do in the lab, surveys for aquatic invertebrates provide a convenient way to quickly assess water quality in the field. Mayflies (Ephemeroptera "short-lived wings"), stoneflies (Plectoptera "folded wing"), and caddisflies (Trichoptera "hairy wings"), hereafter referred to as EPT, are three insect orders that are indicators of high quality water. This means there are sufficient levels of dissolved oxygen, minimal runoff that carries pollutants and silt, and low levels of organic matter pollutants.

Mayflies, as their scientific name would suggest, only have a brief window of time in which they are mature adults. Some species are adults for a few minutes and others just for a few days. Interestingly, these species molt twice to reach adulthood, transforming from aquatic nymph to an immature-winged subimago, where the subimago must use its wings to break out of the water before it can molt once more to become an adult. The Brown Drake (Ephemera simulans), pictured above, comes from a burrowing group of mayflies that have theirs gills located on their back. Once adults, these mayflies can form impressive swarms during the summertime.

Stoneflies (right), are perhaps the most sensitive indicator species of water quality. Common to streams, members of the Perlidae family (above) are predatory on other invertebrates. Upon reaching adulthood, they will "drum" at select frequencies, communicating with potential mates by sending vibrations through the ground. Caddisflies (left), are noteworthy for making homes for themselves. Families can be distinguished from one another depending on the materials and style, and in streams, members of Limnephilidae usually construct their cases out of heavier materials like sand and pebbles. As adults, caddisflies have silky hairs on their wings.

While the method varies by region and agency, the Biotic Index is a common analysis that uses the numbers of EPT and other aquatic invertebrates to calculate a measure of water quality. This achieved by assigning each family of aquatic insects a pollution tolerance rank (0-10, 10 being high pollution tolerance). Then the tolerance rank is multiplied by the number of individuals from each family. This total tolerance per family is then summed across families and then divided by the number of all individuals, resulting in a value between 0 and 10.

Biotic IndexWater QualityDegree of Organic Pollution
Less than or equal to 3.75ExcellentOrganic pollution unlikely
3.76 to 5.0GoodSome organic pollution
5.1 to 6.5FairSubstantial pollution likely
6.6 to10.0PoorSevere organic pollution likely
Table from Stroud Water Research Center

Next time you are out playing in the water, consider looking under a rock or two and see if you can find any of these prized indicator species.

Marshall, Stephen A. 2006. Insects: Their Natural History and Diversity. Firefly Books, Buffalo, N.Y. 718 pp.
Ødegaard, Frode (2000), "How many species of arthropods? Erwin’s estimate revised." Biological Journal of the Linnean Society 71 (4): 583–597
Stroud Water Research Center <>

Thursday, February 27, 2014

No Thanks, I'm Full

Nobody likes a bad meal. You can put in the time, energy, and dedication, yet when all is said and done, what you get is disappointment. I don't know if wild animals experience similar events, but I certainly wonder. For instance, could predators pursue and succeed in catching prey, only for prey to taste bad or have some defense that leaves the predator out of luck? The short answer is yes, but the long answer involves the detailed history of predator-prey interactions: the co-evolution of species' physiology to be in a spy versus spy battle of biological weaponry (think camouflage, claws, armor, or a toxic taste). One defensive tactic, known by all owners of adventurous pet dogs, is the skunk's potent stink spray.

As you can imagine, a pungent stench only really works against something with the ability to smell it. The skunks (Family Mephitidae, "of noxious smell") have two common species in North America--striped (Mephitis mephitis) and spotted (Spilogale putorius). Two additional species exists in the southwest near Mexico, but they are rarer (hooded and hognosed skunk). While skunks have fellow mammal predators such as foxes, coyotes, and mountain lions, they are mainly a food source of last resort for these species. Unfortunately for the skunk, it has a more voracious predator, the great-horned owl (Bubo virginianus). It was probably a great-horned owl that left this striped skunk dead on the road.

Great-horned owls, reliant on their sight and not their nose, can have skunks as the main prey-item in their diet. In some cases, owls will have eaten so many skunks that they and their nests give off the skunk musk. The skunk in the picture above appeared dead on the road after one night. It is hard to see in the picture, but on one side of the skunk, there were two sets of three puncture holes, and on the other side, there were two sets of one puncture hole each. It was clear talons had pierced it. Since skunks are mainly nocturnal, it was most likely a great-horned owl that struck it. Other candidates include red-tailed hawks.  While skunks can become pests in urbanized areas because of available food (trash) and shelter (crawl spaces), they are great consumers of rodents, insects, lizards, frogs, salamanders, fungi, roots, and nuts in their natural milieu.

As seen by its small eyes, skunks have poor vision and instead rely upon
strong senses of smell and hearing.
In the superfamily of Musteloidea, skunks are close relatives of weasels, badgers, otters, and mink.
Thus, it is no surprise that they spend a lot of time in burrows that they have dug.

I'm not sure what exactly happened between the skunk and its owl predator--maybe the owl got spooked by something else and abandoned its kill--but I prefer to think it was an epicurean owl, disappointed by its foul smelling catch.

Sunday, November 3, 2013

Two Forms, Same Plant

What about fossil fuels is fossil? Some might say the "fossil" part comes from the fact that it is a rather outdated source of energy. Driving past the exhausted oil fields of Texas, it could certainly be said that it leaves fossils. Yet, as many of us know, they are fossil fuels because they are the organic, compressed remains of living things from ages past.

The Carboniferous Period. Image courtesy Mark Ryan.

Specifically, most of our fossil fuels come from the Carboniferous Period, which occurred between 359 million years ago (mya) and 299 mya. Appropriately name, "carboniferous" means "coal-bearing". It was a time when arthropods and amphibians dominated terrestrial ecosystems, and it was a time when giant ferns, mosses, scale trees, and ancient gymnosperms densely forested the land. Interestingly by the late Carboniferous the amniotic egg had arisen which opened the door for modern birds, reptiles, and mammals to evolve

Reconstructions of Lepidodendron (far left, Late Carboniferous, ~50 m tall), Sigillaria (left, Late Carboniferous, ~40 m,), Valmeyerodendron (middle top, Early Carboniferous, 0.6 m), Protolepidodendron (top right, Middle Devonian, 0.2 m), Chaloneria (bottom middle, Late Carboniferous, 2 m), Pleuromeia (bottom right, Triassic, 2 m) and Isoetes (bottom far right, extant, 30 cm). Courtesy of Devonian Times and Dennis Clark (c.)
While all of those ancient animals and plants give us electricity, I want to focus on one group of species that are commonly found as the other types of fossils. Lepidodendron, also known as scale trees, grew over 100 feet tall and are most closely related to quillworts and club mosses. The largest fossil found was a plant ~6 feet in diameter. Despite its name, it was not what we would botanically consider a tree today. Considering its height, the plant did not contain much wood at all, and it was supported by an extremely thick, scale-like bark/skin. The scales of the giant tree herb provide for rather iconic fossils--just like the one I came across in the western Appalachian foothills of Ohio.

From what can be gathered from the fossil record, these trees were tightly packed wetland plants. Because of their growth pattern, 1000 to 2000 trees could squeeze into a single hectare. Imagine a giant trunk with a large clump of grass at the top, and you essentially have a Lepidodendron in mind. It wasn't until the plants reached a mature stage that they had branches. It is estimated that these plants reached maturity in 10 to 15 years and would disperse their spores from cone-like structures.

If you want to enjoy Lepidodendron as a fossil and a fossil fuel, you have the best chances of looking near shale rock.

Want to learn more? Take a look at
Stewart, W.N and G.W. Rothwell. 1993. Paleobotany and the Evolution of Plants. Cambrige: Cambrige Univ. Press.
Taylor, T.N and E.L. Taylor. 1993. The Biology and Evolution of Fossil Plants. New York: Prentice Hall.