Organism to Ecosystem Sample

The Dusky-Footed Woodrat, Part 1

           The dusky-footed woodrat (Neotoma fuscipes) lives in the temperate region of western North America (Ingles 1961). Its range excludes mountainous areas and areas of very high and very low rainfall. This is a Mediterranean-type climate (Bailey 1996). Average rainfalls are generally around 50-100 cm per year, but there is a lot of variation. Summers tend to be hot and dry, while winters are cool and moist. The dusky-footed woodrat probably encounters snow very rarely. The soil in its range has been classified as mountain and desert soil, but a variety of soil types are present. Fire is a natural part of this system.

            The genus Neotoma consists of more than ten species of woodrats. The dusky-footed woodrat is a medium-large woodrat of 230-400g (Carraway and Verts 1991). Males tend to be slightly larger than females. All woodrats belong to the family Muridae, the "Old World" mice and rats, even though they are native to North America (Carraway and Verts 1991). The murids are in the order Rodentia in the class Mammalia, phylum Chordata, kingdom Animalia.

Literature Cited

Bailey, R. G. 1996. Ecosystem Geography. Springer, New York. 204 pp.

Carraway, L. N., and B. J. Verts. 1991. Neotoma fuscipes. Mammalian Species No. 386:1-10.

Ingles, L. G. 1961. Mammals of California and its Coastal Waters. Stanford University Press, p 232.

 

 

The Dusky-Footed Woodrat, Part 2

            Dusky-footed woodrats (Neotoma fuscipes) can breed 1-3 times a year and give birth to an average of 2.6 young per litter (Linsdale and Tevis 1951). There are no good longevity data available, but N. floridana can live over 3 years in the wild (Fitch and Rainey 1956). If we assume N. fuscipes live an average of 2 years, half will die each year. If they have 2 litters per year on average, and half are female, their intrinsic rate of increase is about 2.1/individual/year (2.6 born - 0.5 dying). Young are only allowed to nurse for about three weeks. They are a moderately r-selected species.

            The dusky-footed woodrat lives in large dens constructed of sticks which protect it from its many predators. Therefore, the ability of predators to limit population size may depend on den availability (Linsdale and Tevis 1956). Populations decrease during drought (Spevak 1983). Good acorn crops lead to higher densities (Kelley 1989).

Literature Cited

Fitch, H. S. and Rainey, D. G. 1956. Ecological observations on the woodrat, Neotoma floridana. Univ. of Kansas Publications of the Museum of Natural History 8:499-533.

Kelley, P. A. 1989. Population ecology and social organization of dusky-footed woodrats, Neotoma fuscipes. Ph.D. Dissertation. Univ. of California, Berkeley.

Linsdale, J. M., and L. P. Tevis Jr. 1951. The Dusky-footed wood rat. University of California Press, Los Angeles.

Linsdale, J. M., and L. P. Tevis Jr. 1956. A five-year change in an assemblage of wood rat houses. Journal of Mammalogy 37:371-374.

Spevak, T. A. 1983. Population changes in a Mediterranean scrub rodent assembly during drought. The Southwestern Naturalist 28:47-52.

 

 

The Dusky-Footed Woodrat, Part 3

            Dusky-footed woodrats live in areas with dense vegetation, which provides both food and protection from predators. They eat oak (both leaves and acorns), poison oak, sage, and grasses (Meserve 1974). They will eat insects and other foods opportunistically. They store food in their dens. Their major predators are foxes, coyotes, bobcats, long-tailed weasels, mountain lions, spotted owls, barn owls, great-horned owls, red-tailed hawks, rattlesnakes, and feral dogs and cats (Carraway and Verts 1991).

A variety of insects, spiders, reptiles, shrews, small rodents, and amphibians may live in woodrat dens (Carraway and Verts 1991). Deer mice (Peromyscus maniculatus) often live in woodrat dens (Cranford 1982). The mice may occasionally steal food from but can not eat some of the toxic foods that woodrats eat. Desert woodrats (N. lepida) are a competitor for oak and dens. They are smaller than the dusky footed woodrats, which can dominate them behaviorally (Cameron 1971). A variety of parasites live on and in N. fuscipes, including fleas, trematodes, nematodes, protozoa, mites, and botflies (Carraway and Verts 1991). Woodrats can suffer from plague and some carry hantavirus. Mutualistic intestinal protozoa may help woodrats eat toxic plants.
Woodrat Ecological Relationshiops

Literature Cited

Carraway, L. N., and B. J. Verts. 1991. Neotoma fuscipes. Mammalian Species No. 386:1-10.

Cameron, G. N. 1971. Niche overlap and competition in woodrats. Journal of Mammalogy 52:288-296.

Cranford, J. A. 1982. The effect of woodrat houses on population density of Peromyscus. Journal of Mammalogy 63:663-666.

Meserve, P. L. 1974. Ecological relationships of two sympatric woodrats in a California coastal sage scrub community. Journal of Mammalogy 55:442-447.

 

 

The Dusky-Footed Woodrat, Synthesis

            The dusky footed woodrat (Neotoma fuscipes) lives in Mediterranean-type environment, which has hot, dry summers and mild, moist winters. Plants in this climate tend to senesce in the summer or have waxy leaves that resist desiccation. Grasses, sagebrush and oak trees are major components of North American Mediterranean communities. Fires are common in this climate. Grasses are not generally harmed by fire because fires usually burn off tissue that has already senesced, returning nutrients to the soil and leaving roots and seeds intact. Grass fires rarely produce enough sustained heat to cause damage to the oaks. Oaks, sages, and poison oak produce secondary compounds that can be toxic to herbivores and reduce digestibility of their tissues. This may offer some protection from herbivory.

            All woodrats species are very good at dealing with plant chemicals that harm other animals. The dusky footed woodrat has metabolic adaptations that allow it to live on a diet of pure oak leaves. It can also eat poison oak, sage and grasses (Meserve 1974). Mutualistic intestinal protozoa may help woodrats digest toxic plants. There is little competition for this low-quality food, so starvation will generally not limit dusky-footed woodrat populations. This food may take a while to digest, so there is not unlimited energy available to the woodrat. Years of good acorn crops increase woodrat density (Kelley 1989). This may be because acorns are rich in nutrients, so a woodrat can get more energy in a day of feeding on acorns than in a day of eating oak leaves. Populations decrease during drought (Spevak 1983). This could be the result of lack of water itself, rather than a lack of food. Woodrats store food in their dens, so they are probably not affected by temporary food shortages. They get their water from living plants.

The major predators of woodrats are foxes, coyotes, bobcats, long-tailed weasels, mountain lions, spotted owls, barn owls, great-horned owls, red-tailed hawks, rattlesnakes, and feral dogs and cats (Carraway and Verts 1991). Woodrats live in large dens that are constructed of sticks and are often located in patches of poison oak and thorny plants. Only one woodrat lives in each den, but the dens are often the product of several decades of work by successive inhabitants. While it is trying to build a new den a woodrat is vulnerable. Therefore, predation may limit population size, but its effect may depend on den availability (Linsdale and Tevis 1956). Woodrat seem to select areas with over 90% canopy cover (Vogl 1967). This could protect them from large predators.

Woodrat dens provide a cool moist microhabitat. Animals such as invertebrates, reptiles, small mammals, and amphibians seem to take advantage of this (Carraway and Verts 1991). Fungi and plants may also grow there. Deer mice (Peromyscus maniculatus) often live in woodrat dens (Cranford 1982). The mice may occasionally steal food but can’t eat the toxic species.

Desert woodrats (N. lepida) compete with dusky-footed woodrats for oak products and dens. They are smaller, so N. fuscipes can dominate them behaviorally (Cameron 1971). Woodrats are territorial and will steal food from their neighbors’ unoccupied dens (Post and Reichman 1991).

A variety of parasites live on and in N. fuscipes, including fleas, mites, botflies, trematodes, nematodes, and protozoa. Woodrats can suffer from plague, and some carry hantavirus. Epizootics do not seem to cause die-offs in woodrat populations, perhaps because the animals are so solitary. Some fires do not disturb woodrats (Tevis 1956), while others cause heavy fatalities (Chew et al. 1959). Recolonization of badly-burned areas may be slow because of a lack of existing dens and building materials.

Dusky-footed woodrats can breed 1-3 times a year (Linsdale and Tevis 1951). Females give birth to an average of about 2.6 young per litter. Young are only allowed to nurse for about three weeks. Woodrats are a moderately r-selected species. Like all mammals, they get maternal care. They do not get prolonged provisioning, but a mother may tolerate her young living nearby. There is no paternal care. In years when water and acorn conditions are good, populations can expand. In poor years, individuals can supplement their diets with stored food, but may not be able to reproduce. Carrying capacity is greatly affected by the presence of oaks. Woodrat densities may be only 7/ha in chaparral habitats, but get as high as 37/ha if there are also oaks in the area (Vogl 1967).

Woodrats are active mainly at night, when they venture out to collect food (Carraway and Verts 1991). A nocturnal lifestyle allows them to avoid high daytime temperatures and makes them more difficult to see. Their use of a central food storage site means that animals must make several trips to a food source. Woodrats can also climb and they may use trees to escape mammalian predators.

Dusky-footed woodrats do not have many direct interactions with humans. They may be a nuisance if they occupy garages and other buildings. As a prey item of the endangered spotted owl, they may soon receive more public attention.

 Woodrat Ecological Relationships

Literature Cited

Bailey, R. G. 1996. Ecosystem Geography. Springer, New York. 204 pp.

Carraway, L. N., and B. J. Verts. 1991. Neotoma fuscipes. Mammalian Species No. 386:1-10.

Cameron, G. N. 1971. Niche overlap and competition in woodrats. Journal of Mammalogy 52:288-296.

Chew, R. M., B. B. Butterworth, and R. Grechman. 1959. The effects of fire on the small mammal populations of chaparral. Journal of Mammalogy 40:253.

Cranford, J. A. 1982. The effect of woodrat houses on population density of Peromyscus. Journal of Mammalogy 63:663-666.

Ingles, L. G. 1961. Mammals of California and its Coastal Waters. Stanford University Press, p 232.

Kelley, P. A. 1989. Population ecology and social organization of dusky-footed woodrats, Neotoma fuscipes. Ph.D. Dissertation. Univ. of California, Berkeley.

Linsdale, J. M., and L. P. Tevis Jr. 1951. The Dusky-footed wood rat. University of California Press, Los Angeles.

Linsdale, J. M., and L. P. Tevis Jr. 1956. A five-year change in an assemblage of wood rat houses. Journal of Mammalogy 37:371-374.

Meserve, P. L. 1974. Ecological relationships of two sympatric woodrats in a California coastal sage scrub community. Journal of Mammalogy 55:442-447.

Post, D. M., and O. J. Reichman. 1991. Effects of food perishability, distance, and competitors on caching behavior by eastern woodrats. Journal of Mammalogy 72:513-517.

Spevak, T. A. 1983. Population changes in a Mediterranean scrub rodent assembly during drought. The Southwestern Naturalist 28:47-52.

Vogl, R. J. 1967. Wood rat densities in southern California manzanita chaparral. The Southwestern Naturalist 12:176-179.

[9/4/2001]