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The Marvelous Dusky-footed Woodrat

Eek had her first acorn recently. She was so very excited. She hasn't previously experienced acorns because her re-identification as a Dusky-footed Woodrat happened in the Spring, well after our acorn season. Our local squirrels had already efficiently gathered up the last acorn crop. Eek's acorn must have been a squirrel reject, yet she still enthusiastically ate it all.

Many aspects of the Dusky-footed Woodrat species are unexpected and wonderful. Long ago I used to lead trail building crews in the Santa Cruz mountains, and when we came across huge woodrat nests, never actually seeing the occupants, it was easy to envision the owners as multiple large, dark, hostile, scary rodents. They felt dangerous and, because we encountered nests regularly but never saw the rodents, mysterious. Little did we know that the occupant and builder was, incredibly, likely to be just one single, shy female, with soft buff colored fur, a curious yet gentle disposition, and a strong aversion to daylight.

A Dusky-footed Woodrat HouseDusky-footed Woodrats, sometimes termed "nature's architects", are most known for the especially elaborate and large stick houses that they build and live in. A typical home is a conically shaped complex structure, often built against or around protective rocks or stout trees, with internal passageways and "rooms", at least one soft nest chamber protected deep inside, storage spaces for food, multiple entrances, and a midden or refuse pile. Woodrats of all kinds (there are 22 different species, 8 reside in North America) sometimes also use human constructs, like abandoned vehicles and old buildings, as a basis to begin building a home. Woodrat houses are effective at regulating temperature and protecting from the elements, as well as serving as excellent food caches. Unlike the common perception of a "rat", Dusky-footed Woodrats are fastidious in their housekeeping, as well as with their grooming, licking their fur similar to a cat. Some have theorized that the sometimes use of bay leaves in nest chambers helps repel fleas. It is not uncommon for Dusky-footed Woodrat homes to reach six feet in height - pretty amazing when considering the size of little Eek. Note that it is illegal in California to dig up a woodrat den without a permit.

Dusky-footed Woodrats are known to be generally tolerant both of other woodrats and other species. They range about 50-100 feet around their house, often overlapping with other nearby woodrat houses and home ranges. A variety of snakes, birds, salamanders, spiders, lizards, frogs and especially mice, among other animals and insects, also use Dusky-footed Woodrat houses for shelter and protection. Loss or reductions in the woodrat population has a drastic effect on these commensal species, making the Dusky-footed Woodrat what is called a "keystone species".

Usually only one adult at a time lives in a Dusky-footed Woodrat home, though mother woodrats share their homes with their young for the first two months of life. Sadly, woodrats are short-lived, yet their homes may be re-used, generation after generation. Litters contain 1-4 young, who are suckled by their protective mother until they begin to be weaned at about three weeks. Sometimes the young travel with their mother by hanging onto one of her teats. The breeding season is late Winter through Spring, and gestation lasts about 33 days.

If there are an abundance of males in the population, young males may not reach full sexual maturity or physical size. However, once isolated, a previously underdeveloped male woodrat immediately increases its weight and becomes sexually mature. Once a male successfully mates with a receptive female, he builds a separate smaller nest for himself nearby, sometimes, though not typically, in a tree. Once mated, they typically remain together monogamously.

As discussed briefly in an earlier Eekosphere post, herbivorous Dusky-footed Woodrats eat a wide variety of plant matter consuming as much or more than 40 grams nightly, but a few plants, mainly live oak and California laurel, are particular staples. Other mammals, including lab rats (meaning Norwegian rats like Scribble), are unable to handle digesting the toxic tannins in oak foliage, yet these woodrats thrive on it. Researchers at the University of California’s Hastings Reservation in the Carmel Valley tallied 73 plant species in Dusky-footed Woodrat larders. Woodrats climb trees and shrubs nightly to nip off branch tips, then climb down to move the fallen snippets into their food caches within their homes. This pruning seems to have a beneficial effect on native shrubs and plants, encouraging new growth with more flowers and berries. The pruning, foraging and storing habits of the Dusky-footed Woodrat make it one of the dominant propagators of native plants.

Hooray for the marvelous Dusky-footed Woodrat! The more I learn about these wonderful little rodents, the more impressed and fascinated I become. My hope is that you are too.

References:
Dusky-footed Woodrats at Hastings: A Research Tradition: http://www.hastingsreserve.org/mammals/Woodrats/DFwoodrats.html
Dusky-footed Woodrat Neotoma fuscipes (Animal Diversity Web): http://animaldiversity.ummz.umich.edu/accounts/Neotoma_fuscipes/
Neotoma fuscipes, originally published 1991 in The American Society of Mammalogists (Smith College website): http://www.science.smith.edu/departments/Biology/VHAYSSEN/msi/pdf/i0076-...
North American Mammals: Dusky-footed Woodrat (Smithsonian National Museum of Natural History): http://www.mnh.si.edu/mna/image_info.cfm?species_id=214
Neotoma species (San Diego Natural History Museum Field Guide): http://www.sdnhm.org/archive/fieldguide/mammals/neot-lep.html
Woodrats (Internet Center for Wildlife Damage Management): http://icwdm.org/handbook/rodents/Woodrats.asp

The Coast Packrats - the first in a series of fantastic posts about Dusky-footed Woodrats, including amazing camera-trap photos: http://natureofaman.blogspot.com/2012/01/coast-packrats.html

Photo Credit: Dusky-footed Woodrat House by Bob Sutherland, posted in the San Jose Mercury News (http://www.mercurynews.com/gary-bogue/ci_20101404)

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Blog_post | by Dr. Radut