Volen't You Leave My Plants Alone

Voles. While there are 32 species found in North America, there are two primary species in the east that are commonly found in grasslands, woodlands, and your garden. This includes the meadow vole (Microtus pennsylvanicus) and the woodland vole (Microtus pinetorum). While these two relatives occupy different habitats, they play a vital role in ecosystems, and they can have serious effects on habitats when they reach high densities.

The meadow vole is generally larger, reaching almost up to 8 inches. Voles can be distinguished from other rodents by their noticeably short tails. As long as there is dense vegetation at the ground level, meadow voles can be found in most grass dominated habitats north of South Carolina--marshes, fields, meadows, orchards. Interestingly, meadow voles create elaborate tunnel systems in the vegetation called runways. The meadow vole can burrow, but its runways are its hallmark. Along these runways they forage for herbaceous material, seeds, insects, and fungi. Meadow voles exhibit very unstable populations. They can be very abundant one year but barely detectable the next.

I believe a friend of mine put it best: "Meadow voles are like giant ground sloths, man."

Of the rodent world, of course.

Its conifer-named cousin, the woodland vole is a different creature by nature. Unlike the appropriate name of its cousin, the woodland vole, also called the "pine vole" (pinetorum afterall), is rarely found in pine dominated forests.  For the woodland vole, underground tunnels and burrows are the main mode of transportation and food storage. Woodland voles are much more cryptic, as they spend the majority of their time underground. Oftentimes, woodland voles can be found in colonies, but the reasons for formation and disintegration are little understood.

A smaller creature in stature, this species has larger forepaws adapted for digging. 

Both of these species are staple foods for many predators: foxes, coyotes, raptors, and snakes. In some areas, they may be the dominant small mammal and therefore play a significant role in ecosystem energetics. However, these species are probably most notorious for their multi-million dollar destruction of orchards, farm fields, and nurseries. Particularly during the winter, diets in both species shift to bark and root consumption. Sometimes this can lead to the girdling of trees. Gardeners also loath the vole, for their shallow tunnels are often seen leading to dead plants or consumed vegetables. Moles are often blamed for the damage, but moles are carnivorous. 

Even though the meadow vole and woodland vole are important species in their natural habitats, they provide a good example of how wildlife can cause conflict when natural habitats and human habitats meet.

Sources

National Audubon Society. Field Guide to North American Mammals. Alfred A. Knopf: New York, New York.

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.