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. 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.

Sources:

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.