Torpor Affects Us All

Despite the unusually warm winter (2012 being the hottest year on record for the continental U.S.), even I succumbed to winter torpor. Good thing I stocked up some energy with all of the holiday treats!

Diverging from our small-mammal accounts from my time on the Eastern Shore of Virginia, I wanted to provide a quick glimpse at some of the herpetofauna I found while island hopping. It is surprising to think how these animals made it to the islands via saltwater (predators and dehydration) and how they have been able to survey on dynamic ecosystems that are constantly flooding and changing habitat types.

This Eastern Box turtle (Terrapene carolina carolina) was found on Smith Island, which is one of the southernmost barrier islands off of the Delmarva Peninsula. At it's closest point, the island is approximately 2.2 km from the mainland. That is a long way for a terrestrial turtle to go in a harsh environment. Given the number of storms that occur though, it is possible it got blown or swept there. Conant et al (1990) also hypothesized that the turtles might have been brought to the island when it was inhabited by humans up until the 1930s. It seems the population has been able to survive in the wooded areas.

I also came across a rather feisty Black Rat snake (Elaphe obsoleta now Pantherophis obsoletus) while on Mockhorn Island. Mockhorn and Smith occur close together, and the snakes have been documented on Smith Island in the past. Interestingly, this individual was sunbathing on a rather cold and cloudy day. Perhaps it had planned poorly, for it was stranded on a small tump of high ground during high tide. For an instant I expected it to ask for a Marsh Rice rat from one of the Sherman live-traps.

While doing surveys on the mainland, I was also able to glimpse this speedy Ground skink (Scincella lateralis)  "dancing" through the pine needles. These skinks are unusual in that they rarely climb, and they wriggle their body back and forth to move. They can grow up to five inches, so the one in my hand is not all that large.

Switching gears to our amphibian friends, I came across two frog species while working around the field station. The first (above) is a Green Tree frog (Hyla cinerea). The second (below) is a Southern Leopard frog (Lithobates sphenocephalus). The fun thing about the Green Tree frog was that I watched it turn from a bright green to the olive green you see in the picture. This may have been due to an effort to camouflage or because it moved from the sun to the shade. The Southern Leopard frog is simply a nice looking creature.

Sources
Conant, R., J.C. Mitchell, and C.A. Pague. Herpetofauna of the Virginia Barrier Islands. Virginia Journal of Science 41: 364-280.

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.

Sources
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.

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.



Sources:
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.

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.

Sources
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.