Tuesday, November 6, 2012

No Floaties Required aka Mammal Profile Vol. 3: The Marsh Rice Rat

Despite Hurricane Sandy's best efforts, Eastern Shore of Virginia has survived the strong winds and the high waters. Power was only lost temporarily, and the flooding was minimal. To many this may be surprising, but the Virginian section of the Delmarva Peninsula still has many of its natural fortifications. Almost all of the barrier islands off the coast are wilderness, and there are expansive salt marshes between the shore and the islands--not to mention extensive oyster and shellfish beds. All of these reduce wave motion and act as a shield to hurricanes. This is a fine example of ecosystem services, processes which ecosystems perform that benefit humans.

Compared to Norway rats and black rats (the invasive beast and
the grungy city-dweller, respectively) The marsh rice rat is a rather handsome rodent.

But, the real reason we are here is because we want to learn about the robust, ever-versatile marsh rice rat (Oryzomys palustrus, "Marsh/Swamp Rice Mouse"). As it is semiaquatic, these mid-sized rodents flourish in marshes and the Atlantic coastal plains. Their distribution ranges from Texas through the Southeast and some parts of the Midwest, up to New Jersey.

Marsh, marsh edges, and the surrounding uplands all are likely
places to find this species. Here, my colleague J. Sparks works along
one of the trapping lines. 

As their name suggests, they are bountiful in all types of marshes (saltwater and freshwater), and are able to swim great distances, sometimes holding their breath underwater for long periods of time. The longest I have counted so far is 17 seconds. On the barrier island system they have been reported to swim distances greater than 50 meters across deep channels, no easy feat for an animal that is usually smaller than a soda can. Because they are a truly hardy species, the presence of the marsh rice rat is almost the "100% guarantee" of small mammal trapping on the barrier islands we are surveying. Even on islands that are constantly shifting or are barely an island at all, a rice rat will be present. Thus, they are important players in understanding biogeography, the discipline that tries to understand how populations of species vary and function over different landscapes.

After taking measurements, this guy went on a nice underwater swim and hid in the grasses.

Another rat wanted to demonstrate its swimming abilities for the camera. Given that water
causes rapid temperature loss, it is curious to think about how these rodents survive during
colder months after being submerged. It probably has significant energy consequences.

Marsh rice rats are true omnivores and will generally eat most things they come across: plants, seeds, snails, insects, fiddler crabs, mollusks, and some eggs of marsh-nesting birds. They also are an important food  for marsh hawks, owls, snakes, and mammalian predators such as fox and mink. Thankfully, they are not too much of a hassle for human beings. Because of their habitat preferences, they rarely infringe on human endeavors and become pests.

Unfortunately, these animals are quick, and this is the only natural picture I have been
able to capture. These species are also gutsy, inhabiting grassy dunes and making sprints
across open sand.

Linzey, D.W. 1998. The Mammals of Virginia. The McDonald & Woodward Publishing Company: Blacksburg, VA.
Moncreif, N.D. and R.D. Dueser. 1994. Island Hoppers. Virginia Explorer 10(4): 14-19.
Webster, WM. D., J.F. Parnell, and W.C. Biggs, Jr. Mammals of the Carolinas, Virginia, and Maryland. The University of North Carolina Press: Chapel Hill, NC.

Sunday, October 21, 2012

Mammal Profile Vol. 2: The White-footed Mouse

For those who do small mammal surveys, it is never unusual to get a white-footed mouse (Peromyscus leucopus, "Mouse with White-Footed Boots"). Both the white-footed mouse and its close relative the deer mouse (Peromyscus maniculatus "Agile Mouse with Boots") are the most populous mammals in North America. So, while they might not be the most exotic species to capture, they certainly play an important role in ecosystems.

White-footed mice are skilled climbers, sometimes caching food or making nests in
tree hollows. Here, a mouse avoids be weighed by climbing the Pesola scale.

Interestingly, the white-footed mouse has not colonized many of the barrier islands off the Eastern Shore, with the exception of four islands (Assateague, Wallops, Cedar, and Fishermans; Moncreif and Dueser, 1994). While there is certainly great habitat for them, they have not been documented on any of the other islands. This is surprising, as P. leucopus has great homing abilities and has well documented swimming abilities. It could be that the intercoastal water conditions are too prohibitive.

There is no scientific merit to this picture, except that the mouse looks funny while
trying to bite the Pesola scale so that it can escape. Actually, wriggling and biting, besides their speed,
is their only defense once captured by predators.

White-footed mice have also have become a public issue these days. Whether it is because of a change in predators, climate, or habitat composition, white-footed mice have come under increasing attention due to the higher incidence of Lyme disease and hantavirus--both of which they are carriers of. Even though their higher densities equate to human health concerns, the mice play an important role in linking food webs, as they their omnivorous diets are transferred to larger predators like foxes, bobcats and raptors (many of whom consume large amounts of the rodents). Economically speaking, mice consume large numbers of seeds from weed plants as well as insects and generally avoid cultivated areas. Despite this, the wildlife disease consequences of their current success is a central facet of current research.

This species favors hardwood forests as well as the edges of forests and fields. On the shore, they are found in myrtle shrublands and marshes. While typically not hallmarked for their presence in coastal areas, they also seem to abound in drier mixed hardwood-pine forests.

Linzey, D.W. 1998. The Mammals of Virginia. The McDonald & Woodward Publishing Company: Blacksburg, VA.
Moncreif, N.D. and R.D. Dueser. 1994. Island Hoppers. Virginia Explorer 10(4): 14-19.
Webster, WM. D., J.F. Parnell, and W.C. Biggs, Jr. Mammals of the Carolinas, Virginia, and Maryland. The University of North Carolina Press: Chapel Hill, NC.

Saturday, October 6, 2012

Mammal Profile Vol. 1: The Least Shrew

Whum chakka um chakka chumchakka whum!
Guosim dig yore paddle deep,
Hurly-burly river wide'n'curly,
There's no time to sleep.
Whum chakka um chakka chumchakka whum!
Rapid wild and fast do go,
Hurly-burly river wide'n'curly,
Bend yore backs an' row.
Whum chakka um chakka chumchakka whum!
Keep her bows up in the foam,
Hurly-burly river wide'n'curly,
Logboat take us home.
Whum chakka um chakka chumchakka ...

-Paddling Song, Guerrilla Union of Shrews In Mossflower, Marlfox by Brian Jacques

I'm not sure if you have read any of the books in the Redwall series by Brian Jacques, but as the main characters are mostly small mammals, you can bet I will shamelessly make references to the series during these mammal profiles (If you haven't heard of the series, it is similar to Watership Down).

So far during our trapping endeavors, we have captured 5 different species of small mammals. One of my favorites, the least shrew (Cryptotis parva, Greek and Latin for "small hidden-ear" shrew), is the first animal I'm going to discuss. The least shrew is in the diverse and complicated order Insectivora (insect-eating and carnivorous mammals). Within that order, they are classified in the Soricidae (shrew) family, a group containing some of the smallest mammals. Characterized by their small eyes, pointed teeth, and long tapered snout, this species relies mostly on its sense of smell and hearing to move and locate prey.

Least shrews are very vocal, using clicks and squeaks to communicate.
In this case, they are mostly communicating, "Stop weighing me and let me go."

The mammals are very small, growing up to 92 mm in length--including tail--and weighing up to 5.7 grams, the weight of a nickel. Although small, they are voracious eaters and busy critters. They are almost always active and only have short periods of rest. Part of this arises from an incredible metabolism: having to eat 50% of their weight or more every 24 hours. The least shrew consumes large amounts of arthropods, worms, and other insects. For some insects that are too large to consume whole, the shrew will eat out the insides. They also are a food source for many other animals, including snakes, raptors, foxes, and skunks.

While the least shrew is often confused with members of the short-tailed shrew genus (Blarina), the least shrew is distinguishable by its tail, which is less than half the length of its body and head. Behaviorally, the least shrew also is rather social, as nests can have up to two dozen individuals. These nests are usually found near logs, rocks, and debris, and they are made out of shredded grass and leaves.

 Unfortunately, due to their energetics, it is not rare to have shrew mortality.
Sometimes the shrew cannot survive the time in the trap, but all possible measures are taken to avoid it.

The old-field habitat in which we surveyed and found the majority
of our least shrews.

The least shrew is mostly found in dry, open grasslands, but they also are found in saltwater marshes.  Typically, the Sherman live trap is not the best method to capture shrews, but we set the trap's trigger to close at a lighter weight.

Linzey, D.W. 1998. The Mammals of Virginia. The McDonald & Woodward Publishing Company: Blacksburg, VA.
Webster, WM. D., J.F. Parnell, and W.C. Biggs, Jr. Mammals of the Carolinas, Virginia, and Maryland. The University of  North Carolina Press: Chapel Hill, NC.
Schemnitz, S.D., 2005. Capturing and Handling Wild Animals. In C. Braun (Ed.).Techniques for Wildlife Investigations and  Management (pp.239-285). Sixth Edition. The Wildlife Society: Bethesda, MD.

Tuesday, September 25, 2012

Settling Down and Shoring Up

Well, it has taken me a while to write another post, but I am back! My position at the refuge in New Jersey wrapped up nicely, and I have settled into a new job on the Eastern Shore of Virginia.

The Eastern Shore, formally known as the Delmarva Peninsula, has the Chesapeake Bay 
to the West and the Atlantic Ocean to the East. Note the barrier islands. Image from Google Earth.

The project I am working on is part of the Virginia Coastal Reserve Long-term Ecological Research (VCR-LTER) initiative. While this initiative has a variety of components, I am specifically working on small mammal surveys (voles, mice, shrews, rats) with a professor who has researched the shore's ecosystems for many years.

The project will take place across the shore: 2 mainland sites and 19 or so barrier islands. Part of the study will compare small mammal diversity to surveys conducted approximately 20 years ago. Having a benchmark of the species currently found on the islands will also provide good reference for similar studies conducted in the future. The barrier islands provide many ecosystems services, and they are rapidly changing in habitat composition and size. Thus, the small mammal work will help in understanding the biogeography and ecology of the greater barrier island ecosystem.

My colleague, J. Sparks, working on reinforcing trap boxes, attaching straps,
and soon to be waterproofing them. Each box holds 32 folded traps.

Before trapping can occur though, the equipment had to get arranged. As some sites will have upwards of 200 traps, solid preparation is key. The type of traps used are collapsible Sherman live-traps, which are are effective at capturing small mammals and also are a survey method that have relatively high capture rates.

Getting everything together involves preparing trap boxes to carry them in, cleaning the traps, making sure all parts of the traps function, and creating the baits for the traps. Normally, baits for these traps are peanut butter and a grain (like rolled oats); however, our trap baits are a combination of shortening (Crisco) and cracked corn, both of which are easy to digest by the animals and also reduce trap mortality during cold temperatures.

Extra baits will be used for trick-or-treaters on Halloween.
They look close enough to candy. Just kidding.

 Using a GPS to mark the beginning of a transect and to
set a bearing. Then the line is laid and flagged.

Before traps are armed and ready for critter abduction, they are laid in transects (lines) that run through multiple habitat types to survey all small species at a location. Traps are then fixed open and baited to attract but not capture the mammals. Once they have acclimated to the presence of the traps (~48 hours) the arming of the traps ensues (and the results of those endeavors will be shared later!). All animals captured are released after measurements are taken.

 The bait is hung inside the trap from the back door, forcing the animal
to walk generously on the treadle which trips the front door. For baiting,
a tongue depressor is used to prevent the closing of the front door.

 Complete with holly and pine-straw landscaping, here is what the
Sherman trap looks like all set up.

On the next post I will begin the first of many species accounts from the animals we capture during the surveys.

Dueser, R. D., W. C. Brown, G. S. Hogue, C. McCaffrey, S. A. McCuskey, and G. J. Hennessey. 1979. Mammals on the                       Virginia barrier islands. Journal of Mammalogy 60:425-429.
Dueser, R. D. and W. C. Brown. 1980. Ecological correlates of insular rodent diversity. Ecology 61:50-56.
Schemnitz, S.D., 2005. Capturing and Handling Wild Animals. In C. Braun (Ed.).Techniques for Wildlife                                                 Investigations and Management (pp.239-285). Sixth Edition. The Wildlife Society: Bethesda, MD.

Saturday, July 21, 2012

A Stick in the Mud

            In 1973, the Endangered Species Act (ESA) was passed by the Nixon administration in order to protect rare and declining wildlife across the country. Without this legislation, many species would undoubtedly be in more trouble than they already are. Since its passing, 28 species have been delisted due to recovery, including the bald eagle, the grizzly bear, and the american alligator (USFWS, Delisting Report, 2012.

As the bane of developers, the ESA stipulates that there cannot be any actions taken to harm populations of threatened (T) or endangered species (E)—threatened meaning is likely to become endangered, endangered meaning in danger of extinction—or the ecosystems in which they reside. It is a rather involved process to get a species listed under federal protection via the US Fish and Wildlife or NOAA, but once protected, there are serious consequences for harming a T&E species.

An adult bog turtle with the mud rinsed off. Notice the orange cheeks.                  

            A current threatened species that I have gotten to work with is the bog turtle (Gleptemys muhlenbergii “Muhlenberg’s Carved Turtle”), which has separate populations in the Southern Appalachian Mountains and the Northeast. Occupying bogs, swamps, and wet meadows, the bog turtle requires slow-flowing rivulets and mucky, organic soil. Their habitat has some of the richest plant diversity, with small bogs or wetlands having over 150 plant species. Because of their habitat requirements, this species has declined as wetlands have been drained, cultivated, and developed.

      A bog turtle nest (above) is usually laid right in the middle of a tussock sedge, so that it can incubate.      
Between predators, weather, and other factors, only about 27% of eggs make it to hatchlings (below).

             Considering bog turtle habitat, it is no wonder the species are declining. Walking through the bogs, one can sink two feet into muck while trying to avoid poison sumac. Surveying for turtles can involve trapping with wire boxes, or, more commonly, probing in the mud. You would never guess that poking around in deep mud will yield turtles. The trick is learning to discern the “thud” of hitting a submerged root from the “thwok” of a rock from the hollow “thunk” of hitting a bog turtle carapace.

Imagine trying to hit that shell through a foot of mud without knowing what exactly you
are hitting. A sometimes frustrating, but rewarding, treasure hunt.

            Once found, the turtles are notched, measured and released so that the overall population can be estimated with mark recapture analysis. If a turtle is lucky, it will get decked out with a radio transmitter. I can’t decide if the transmitter is poorly respected (like a dog with a head-cone), or highly prized (like a geek with the newest gadget). Anyways, tracking and recording the locations of the turtles using radio telemetry help scientists understand how much habitat is required to sustain a population and what type of sub-habitat, or microhabitat, the individuals prefer.

An adult bog turtle with a radio transmitter attached to the carapace.
The transmitter is placed on the side of the posterior so that it does not hinder movement or mating.

            All in all, the bog turtle is a very neat species, burrowing and moving around underneath mud and adding a little character to a rare and unique habitat.

Information on bog turtles taken from studies reported in Turtles of theUnited States and Canada by Ernst and Lovich

Saturday, July 14, 2012

On the Road Again

(Disclaimer, if you don't like animal guts, skip this post).

Also, double post this weekend, so don't miss “Quoth the Marsh”

Most normal people would not consider any road kill all that special, particularly if it is a snake. Even though I am human, I most likely wouldn't fit the bill for being normal. Naturally, when I saw a Eastern Common Garter Snake (Thamnophis sirtalis sirtalis) dead on the road, I had to pull over and snag it.

 The specimen in question. Depending on the subspecies,
it can take two the three years before females can reach reproductive maturity

Now, even further from being normal, I decided to dissect the snake so that I could try and get a whole snake skeleton to put together as a model. It was also a unique opportunity because she was gravid, and you could feel the embryos in her gut.

Common Garters are not having too hard of a time compared to most snakes, but it is still sad to see a gravid female killed by a car. There were a total of five embryos inside her. Garters are ovoviviparous, meaning that they produce offspring within an amniotic sac and give live birth. It takes 80 to 90 days for gestation to occur (depending on environmental temperature), and a female can birth between 1 and 101 offspring depending on size and maturity. Females will only breed bi-annually or tri-annually. 

One of five embryos inside the snake. It's rare to get to see offspring
mid-development. The top picture shows the developing snake inside its own membrane.
The second shows it outside of the membrane.

Interestingly, the Common Garter snake is the northernmost snake species in North America. This is because it can tolerate a wide range of temperatures and can even survive being frozen for brief periods of time. Found in a variety of different habitats, the snake is most commonly found near wet areas. As there are many subspecies of this snake, coloration, diet, and behavior can vary drastically.

The Common Garter Snake is also the most deeply studied snake in North America.

For more info, see Snakes of the United States and Canada by Ernst and Ernst

Quoth the Marsh

As the main research branch of the United States government, the US Geological Survey (USGS) does a lot more than look at rocks. They produce many of the research protocols that the National Wildlife Refuge system follow, and this includes the monitoring of many different taxa: streamside salamanders, vernal pool amphibians (see post), songs birds, waterfowl, and many more.

These guidelines for wildlife monitoring mean that nationwide, there are standardized surveys going on, giving the USGS significant insight as to how wildlife populations and species distributions are changing. One of the surveys that we have conducted as part of these protocols include “Secretive Marsh Bird” surveys.

Walking to the first marsh for surveying. Multiple marsh locations are done within
a 4-5 hour window of time during specific weeks of the year.

Like many bird surveys, early morning hours are required, and in this case, they are required along with a portable speaker system. Many of the birds that are obligate marsh birds—meaning they are only found in marshes—are extremely hard to see. In order to survey for them, we play a sequence of bird calls with hopes that these birds will return the call. As with many birds, secretive marsh birds are territorial. Thus, they think the call we play is an obnoxious intruder, and it is their duty to let the intruder know that turf (or surf?) is already taken.

 Clapper Rail. Photo by L. Meyers

 Green Heron. Photo by M. Godwin.

Some of the species that are targeted include the Least Bittern, American Bittern, Sora, Green Heron, Virginia Rail, and Moorhens, and Clappers. While many people think of Great Blue Herons when they think of marsh birds, Great Blues are not considered obligate marsh species, as the herons can be found along streams and other habitats as well.

Least Bittern. Photo by 50birds.com

Saturday, June 16, 2012

A Bear of a Time

Two weeks at the refuge so far and things are going smoothly. I put out a camera trap almost as soon as I got here and so here is my pull from the first week. Given that the refuge is along ten miles of river corridor, I'm hoping for some good results this summer.

This is my first picture of a bear so I'm pretty excited. Here in New Jersey, there are bears everywhere, and it is not uncommon to see sows with four or five cubs (that's unusually high). This year there is going to be another bear hunting season, but hunting bears has been a fairly political issue in the state in the past. From what I've gathered, the American Black bear (Ursus americanus) is overpopulated here.

Two Coyotes (Canis latrans) made a run through, and a brave white-tailed deer
followed only a few minutes behind.

And to finish things off, a comical picture of the woodchuck (Marmota monax): also
known as the land beaver, whistle-pig and groundhog.

Saturday, June 9, 2012

Snake, Rattle, and Roll

These past couple of weeks have been fairly busy (and it wasn’t the Avengers movie this time, although Men in Black 3 was entertaining); instead, I have recently returned from an adventure to the northern Midwest. Shortly upon returning home, I packed everything and moved up to New Jersey. I will be in the Garden State for the summer, working at Wallkill River National Wildlife Refuge.

While on my adventure, I had the pleasure of exploring some great prairie bluffs with a variety of folks. Without them, my trip would have not been nearly as fascinating or rewarding.

We looked a few different places for the snakes, and it looking through brush and under shelf-rocks.
Venomous snakes should never  be handled with bare hands, so snake hooks were used hold them and
release them.

Perhaps my favorite one of my favorite experience was finding my first wild rattlesnake. In this case it was the timber rattlesnake (Crotalus horridus “The horrid rattle tail”). Like many of the world’s critters, these snakes are declining across their range in the Midwest, South, and Northeast. Besides its loss of habitat, snakes receive a fair amount of persecution.

 The famous rattle of the rattlesnake. This individual had a surprisingly large rattle,
as they can often break.

The timber rattlesnake, which can grow up to almost 6 feet, has been exterminated by shotgun, by car (snakes are an easy target on the road), and by yearly roundups in some locales (killings of almost entire snake populations). Historically the snake was considered for our national animal (think “Don’t Tread On Me”), and Benjamin Franklin considered the timber rattlesnake to be of higher character than the bald eagle.

Timbers are relatively rare, are secretive, and are mild-mannered compared to other vipers (like many other venomous snakes, timbers have infrared sensing “pits” nears their eyes and nostrils”). They like south-facing woodlands, montane regions, rock shelf, pine savanna, and swamps.

A brief video of one of our encounters. This dude suprised us while he was basking,
and then he headed straight for his home under the boulder.

While timbers are often killed because of the fear they impose, they rarely bite humans unless greatly provoked. Sometimes they will strike defensively with a closed mouth. Mostly, timbers use their potent venom to hunt small mammals—namely mice (38%) and chipmunks/squirrels (25%). Interestingly, timbers only eat 6-20 meals annually, and over a year, they eat twice their body weight mass. I have to say, I would love my grocery bill if I could eat that little. Unfortunately, I will never have the metabolism of an ectotherm.

All facts were from publications found in Snakes of the United States and Canada authored by Ernst and Ernst.

Monday, May 14, 2012

Land of Ghosts

Whew, so between finishing my thesis, taking exams, and having to see the Avengers movie, I haven't been able to update in a while. To compensate, I've got a longer post today that I wrote similar to an article you would find in the magazine Natural History. I hope you enjoy!

           What would the African savanna look like without the lion? What if, when visiting the great parks like Yellowstone, there were no grizzly bears, wolves, or mountain lions? How intriguing would the ocean be without sharks or whales? What magic would be lost if the jungle was tiger-less? While these questions spark the imagination, there is a real danger of a world without the great predators.
            Since humanity’s beginning large carnivores have played an important role in human psyche and cultures around the globe. Perhaps it is their size, or the fear they inspire in us, that makes them charismatic and mystical. In the Himalayan Mountains, the snow leopard is central in the Buddhist and indigenous beliefs. In North America, the Yukon Indians believed they attained their knowledge of how to live from the bears. Yet, as time went on, the fate of large predators changed. The animals that transfixed us soon became enemies of progress.

           Top predators have played a significant role inculture and religion. A Tibetan illustration of 
the snow leopard mythically depicts the elusive leopard of the Himalayas.

            That sentiment survives until today. As more and more research is being done, it is clear that our great carnivores are beginning to disappear. The loss of the large predators is not merely an exercise in imagination. Wild tigers are likely to be extinct in the next ten years. Lions have witnessed a 95% decline in the last fifty years. Wolves precariously balance on the edge, but are fortunately protected by the federal Endangered Species Act. Almost a third of all shark species are on the brink of extinction. Needless to say, large carnivores are on the decline, and the conservation efforts to save them are slow-going.
            Bringing the large carnivores back is a tricky process. The public can be scared of them, they often conflict with agricultural live-stock interests, and they have large habitat requirements. Cougars, for instance, need 85 km2 in order to have enough resources to survive. As human populations grow, the large tracts of land needed for the terrestrial carnivores are being transformed into subdivisions and are being fragmented by roads and highways.
            But, what is really the problem of losing the large carnivores? Kids dream of sabre-tooth tigers and dinosaurs, so it would be tragic for them to yearn for sharks and other predators too. Yet, the loss of important predators has larger impacts than nostalgia, though. A new paradigm has been emerging in the scientific world. Its momentum has been slowly increasing since the 1960s. This novel concept is called trophic cascades, and it means apex predators do a lot more to shape the world around us than we realize.

The loss of sabre-tooth tigers were thought cause trophic cascades during
the Pleistocene.

           Trophic levels are an ecological concept that help elucidate how energy flows through an ecosystem. Plants and plankton are at the bottom of the trophic pyramid, and they produce all energy and matter in an ecosystem through photosynthesis. Herbivores eat the plants, and they comprise the next tier. Add on different levels of predators and you eventually make it to the top, where apex predators reside. The animals are the top of the food chain, but because of their energy (trophic) requirements, only a certain amount of them can reside in an individual habitat.
            Ecologically, there are always a variety of patterns between predator and prey. Most simply, when predators increase, prey decrease, and a dynamic balancing act ensues. But, dramatic changes can occur when predators are removed altogether. Top-down control of an ecosystem is removed, and this relieves pressure off of prey populations, sometimes allowing their numbers to increase dramatically. I think about where I live, in the Piedmont of North Carolina. Our large predators have been missed for quite some time—the wolf, the mountain lion—and those important ecological roles have been passed down to animals who can’t handle the work load—black bears, coyotes, and bobcat.
As a consequence, populations of white-tailed deer and rodents have exploded, and the effects of their new hegemony are not beneficial. Of course, we don’t like the increased chances of deer-related car accidents or the higher prevalence of tick-borne illnesses, but their effects are even more wide-ranging than that. Deer are constant grazers, and they will graze any area to where they can no longer reach. This leaves a dramatically altered understory for the rest of the animal community. It is as if someone moved into the neighborhood, bought all of the nice homes, and left all of the lower quality homes for everyone else. Deer not only over-consume plants that comprise other animal’s shelter, but they also only leave plants untouched that are unsuitable to be eaten by other organisms.

White-tailed deer can be found in overabundance throughout much of the eastern
parts of the US.

For the Piedmont, and for other areas of the United States where this problem occurs, the effects can be ecologically staggering. Researchers have discovered that these irruptions of white-tailed deer are depleting herbaceous plants and reducing the recruitment of oaks and hemlocks. This changes the resources available to other wildlife, such as song birds and mast consumers. Because the predators are gone, there is not much else to keep the deer in check year-round.
While the white-tailed deer are the consequences of predator loss in my backyard, trophic cascades are occurring around the world. It wasn’t until the 1960s that the idea even took hold in the ecologist community, and since then, the evidence of trophic cascades has been mounting. Originally, ecologists thought that ecosystems are structured by plant or plankton productivity. The types of plants, and how quick they grow, determine what lives where. However, in 1960, Hairston, Smith, and Slobodkin (HSS) developed the “green world” hypothesis: the planet is green because there are predators that prevent herbivores from eating everything.
It wasn’t until Robert Paine began a study on the Olympic Peninsula of Washington State that ecologists began to tentatively accept HSS. In a study on rocky coastal communities, Paine elegantly discovered that the ochre sea star (Pisaster ochraceous) played a key role in stabilizing the ecosystems on the rocky outcrops of the coast. Paine visited different rocky outcroppings each month, and at one site, he would toss all of the sea stars he found back out into the sea. He left the other site alone.

The ochre sea star has a variety of colors and can dominate
habitats on the rocky, tidal coasts of the Pacific Northwest.

As the ochre sea star is the top predator in those habitats, they consume all sorts of marine invertebrates. It did not take long for Paine to realize what effect removing the top predator was having. Whereas the plot he had left untouched retained a diverse cast of characters—various species of limpets, barnacles, snails, and mussels—the plot without the sea star had changed dramatically. The California mussel (Mytilus californianus) had nearly taken over the whole rock. With its top predator gone, the ecosystem collapsed from a diverse assemblage to a habitat dominated by one species.
By removal of the apex predator, Paine showed that changes cascaded down through all trophic levels in the ecosystem. Marine filter feeders (herbivores) and low-level predators were all lost due to the dominance of one species. Perhaps the California mussel is like the white-tailed deer in that sense. Without apex predators, ecosystems diminish in biodiversity for both plant and animal communities, and these alterations to a habitat can change the face of the landscape.
Unfortunately for ecologists, not all ecosystems and trophic interactions are as simple as the ochre sea star and its coastal rocky habitat. Especially in terrestrial habitats, top predators move from one community to another, often becoming a temporary resident where conditions are favorable. Thus, they can be a stabilizing influence for more than one community. Terrestrial ecosystems also have many players filling many niches, and the more complicated a system is, the more difficult it is to discern distinct trophic relationships.
            In 1995, from a combination of blood, sweat, and tears, scientists and conservationists provided the opportunity of a lifetime. In 1926, the last two wolves were killed in Yellowstone National Park, and in 1995, eight wolves from Canada were re-introduced. A lot had changed in those seventy years in the wolf’s absence. The riparian habitat had been degraded, for the cottonwoods, aspens, and willows had failed to flourish. The streams were eroding away. The culprit was the elk (although ecologists didn’t realize it), whose populations swelled so high that even staff of the National Park Service could not cull the herds well enough to restore the ecosystem’s balance.

Scientists and members of federal agencies carry a
wolf to release for reintroduction.

            What Aldo Leopold had suggested 50 years earlier finally came to being with the introduction of the eight wolves (Canis lupus).Yellowstone once again regained one of its most important members. Currently, the wolves have reached a population of 98 individuals, and the changes that have occurred in the Greater Yellowstone System are dramatic. Coyote populations have been reduced by half, so their thieving of newborn pronghorn antelope dropped and the pronghorn entered a revival. Fear of predation allowed the riparian trees to thrive as elk shifted their foraging patterns to avoid the wolves. With the trees came songbirds and beavers.

The presence of wolves have dramatically influenced the landscape
of the Greater Yellowstone System.

            The two scientists who have led the research on wolves and trophic cascades, Bob Beschta and Bill Ripple, have also replicated the Yellowstone reintroduction with many other national parks in the West. While many scientists were slow to accept that the wolves could be having an effect to such a large extent, Beschta and Ripple continued to press on in their studies, and now it is well accepted the canid pack-hunters are essential architects of the ecosystem.
            Trophic cascades are a concept that originally started as the revolutionary green world hypothesis of HSS. Today, it is a well established fact that top predators and producers are equally significant in how they affect the composition of an ecosystem; although, there are still some last redoubts who resist this new paradigm. Nonetheless, in the quest for conservation, protection of biodiversity, and responsible stewardship, top predators cannot be ignored. While we have only discussed the dynamic between predator and ungulate herbivores, there are a variety of other detrimental effects absent predators can cause.
            Without the apex predators, mesocarnivores can explode in abundance. This includes North American mammals like raccoons, opossums and the feral housecat. With the larger populations of mesocarnivores, local extinctions of plants and small animals (herpetofauna, birds) can occur. Disease can also become a larger issue. I wonder if trophic cascades haven't led, in part, to the rabies epidemic that has occurred throughout the Southeast.
            The dynamic of trophic cascades are not strictly tied to terrestrial systems either. Large marine vertebrates have also declined dramatically. Some of the great whales, sharks, and tunas have declined dramatically. Those that remain have been scattered into small nomadic groups or failing fisheries. James Estes found that sea otters (Lutra lutra) regulated sea urchin populations, allowing the giant kelp forests (Macrocystis pyrifera) to grow. Kelp forests are one of the richest marine ecosystems. However, with primary food sources for killer whales (Orcinus orca) declining, the killer whales have shifted to consuming otters. The existence of Pacific kelp forests hangs in-between. Other studies done in the ocean have also shown that losses in apex predators alter the productivity of algae, the abundance of fish, and even the patterns of ocean currents.

Without their normal food sources, killer whales could cause
the collapse of kelp forests.

            So, what do we do now? The decline of top predators at the hands of society leaves us with a duller world to say the least. Their absence also leads to severe economic problems for agriculture, forestry, fisheries, etc. Thus, when we think about what must be protected, the apex predators of the sea and land must be a top priority. Otherwise, in combination with climate change and the myriad other environmental issues looming ahead, the loss of top carnivores could cause ecosystems worldwide to shift to alternate states that leave something to be desired. If the top predators are lost for good, then we will see a world of broken ecosystems manifest, and only we will be able to see the ghosts of mighty creatures that once roamed.

(Because it was written as an article, there are no citations, but all information was gathered from "Where the Wild Things Were" by William Stolzenburg and from "Trophic Cascades" edited by Terborgh and Estes. Also, I do not have rights to any images used in this post except the deer).

Tuesday, April 17, 2012

Birds and the Bees, Sallies and the Streams

Well, not streams per se. But, with it being the season of pollen, green-up, and breeding comes the great breeding migration of the Spotted Salamander (Ambystoma maculatum) and the hatching of the Marble Salamander (Ambystoma opacum). Since the winter was so warm, breeding came early. In February, larvae of both species were swimming around in the vernal pools of Piedmont.

 A Spotted Salamander egg mass floating and hidden among vegetation.

The Marbled and Spotted Salamander have larvae that are deposited as eggs into vernal pools throughout the Southeast,  parts of the Midwest, and parts of New England. The Spotted Salamander's distribution also reaches into areas of Canada (Conant & Collins, 1998). Vernal pools, sometimes called ephemeral ponds, are seasonal wetland depressions found in woodlands. They fill during the winter and spring, and they dry during the summer and fall. Because they dry out, no fish can inhabit them--perfect breeding grounds for amphibians.

In the Piedmont of North Carolina, the hatching of the eggs for both species occurs simultaneously, and it can be difficult to distinguish between the two larvae. However, the Marbled Salamander larvae have black pigment on their throats and are typically larger (Mitchell & Gibbons, 2010). Both species have bushy external gills, tails for swimming, and two well developed forelimbs. Hind limbs develop during the larvae stage.

 Two Marbled Salamander larvae. 
Notice the tiny hind limbs and external gills.

The fascinating thing about these two species is not their aquatic larvae. Instead, it is the amazing journey the adults undergo in order to mate every year to two years. Both species are the only salamanders to mate on land. Marbled Salamanders migrate after mating occurs in October or November, and they lay their eggs in the dried ephemeral ponds. The eggs will only hatch after being inundated (Petranka, 1998).

 A Salamander larvae in its natural habitat, 
unaware of the looming net about to scoop it up!

Even more dramatic than that, Spotted Salamanders will migrate to breeding grounds during moist nights in late winter and early spring and will lay their eggs in flooded pools. It is unknown as to how salamanders orient themselves directionally, but they can travel great distances (200m-500m) to meet for the mating season (Petranka, 1998). For something only 22cm, that is a long way to go! Imagine having to go 900 to 2250 times our body size to find a mate.

 An adult Spotted Salamander. Found under a log
next to the vernal pool.

Unfortunately, given the migration patterns of the salamanders, there are great concerns for the survival and conservation of the two species. Besides the loss of ephemeral pools, habitat fragmentation by roads has isolated adult habitats from breeding grounds. With the small size and slow movement of salamanders, it is easy for them to be killed by motorists.

Hopefully you will have the chance to see one of these fantastic creatures! The best part is that they can be as far away as your backyard or local park.

Works Cited

Conant, R. and J.T. Collins. 1998. Reptiles and Amphibians of Eastern/Central North America. Houghton Mifflin Company, Boston, MA.

Mitchell, J.M. and W. Gibbons. 2010. Salamanders of the Southeast. University of Georgia Press, Athens, GA.

Petranka, J.W. 1998. Salamanders of the United States and Canada. Smithsonian Institution Press, Washington D.C.

Saturday, March 3, 2012

The Clown in the Forest

Sometimes there are animals that do the most silly of things. Maybe its because it reminds us of the foolish side inside ourselves. Maybe the humor arises from astonishment ("That animal is doing WHAT?"). From my experience, raccoons seem to be clever, mischievous, and rather comical. From cameras that I've used to study mammals in central North Carolina, I've gotten some great pictures of raccoons up to nothing less than shenanigans. Raccoons, Procyon lotor, are perhaps familiar to most folks as the annoying critter that stalks the bird feeder at night or harasses your neatly tied trash bags.

Raccoon tracks (both adult and kit). The hand-like forelimbs correspond
with highly sensitive pads, giving the raccoon one of the most acute
senses of touch compared to other carnivores (Iwaniuk & Whishaw, 1999).

In this sense, raccoons deserve some respect, for not many species are able to adapt to and take advantage of the encroachment of civilization on their natural habitat. Raccoons are smart, and because they are generalists, their distribution ranges across almost all of North America. Whether on the ground or in the trees, raccoons are adaptable to a variety of habitats.

Yes, even raccoons have to deal with paparazzi. Interrupting some acorn foraging
where raccoons will dig through leaf litter to find goodies.

Primarily, raccoons feed on acorns and other plants, but they are also avid fishers, bird hunters, insect stalkers, and mollusk consumers (Stuewer, 1943). The raccoon does not tread freely however. Being a mesocarnivore (an intermediate predator in the larger food web), raccoons have to be particularly wary of coyotes (Canis latrans), bobcats (Lynx rufus), owls, and alligators (Alligator mississippiensis) (Gehrt, 2003).

Nonetheless, and pardon my anthropomorphizing, here are some entertaining pictures of the coon finding time to have fun.

Don't be embarrassed by your offspring. This cub tries to show off some gymnastic skills,
or it it merely overestimated the size of the branch. It's mom can only be so proud.

And for my favorite, here is the ninja raccoon (he's got a mask and everything!). Enjoy his clumsiness stealthy expertise in navigating the tricky way of the woods.

Works Cited
Gehrt, S.D. 2003. Raccoons (Procyon lotor and Allies). In G.A. Feldhamer, B.C. Thompson,  & J.A. Chapman (Eds.). Wild Mammals of North America: Biology, Management, and Conservation 2nd Edition (pp 661-634). John Hopkins University Press. Baltimore, Maryland. 
Iwaniuk, A.N. and I.Q. Whishaw. 1999. How skilled are the skilled limb movements of the raccoon (Procyon lotor)?  Behavioral Brain Research 99: 35-44.
Stuewer, F.W. 1943. Raccoons: Their habits and management in Michigan. Ecological Monographs 13: 203-257.