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Neotoma fuscipesdusky-footed woodrat

By Christopher Bonadio

Geographic Range

The range of the dusky-footed wood rat is restricted to the Pacific coastal area of the United States and Lower California. The range specifically extends from the Columbia River in Washington southward through the Sierra San Pedro Martir of northern Lower California. Toward the east, the dusky-footed wood rat's range reaches the Cascade-Sierra Nevada mountain system and the Mojave and Colorado deserts. In terms of altitude, this species lives at elevations of around 9,000 feet in the southern areas of its range.

Habitat

The dusky-footed wood rat, although found on hillsides, usually select valleys and lives very close to small streams and water. Since this species likes areas that are covered, they tend to avoid open grassland and open oak woods with small amounts of underbrush. The plant species in the area affect the wood rat through the nature of the cover and screening it offers. Plants such as Arroyo Willow, Red Willow, and Coast Live Oak provide good protection.

Besides the biotic features of a habitat, there are also abiotic features which contribute to the nature of the dusky-footed wood rats' habitat. Light is avoided even when it is as weak as moonlight. Cold air is more suitable than extreme heat. When temperatures approach one hundred degrees fahrenheit, wood rats move to cooler places. Dryness of a wood rat's coat is important for maintaining good health, but low humidity is unfavorable. Within their habitats, rats live in colonies of three to fifteen or more nests (homes).

Physical Description

The fundamental pelage color of dusky-footed wood rats is cinnamon with variations toward tints of buff and pink. Every dusky-footed wood rat has vibrissae (whiskers) that are disposed in six parallel, evenly spaced rows. The ears are thin, large, rounded, and broad as well as hairy. The claws are short, sharp, curved sharply downward and almost equal in length. The claws are also colorless. There is some sexual dimorphism in this species. Females are about 38.5cm in length (including the 18.7cm tail). Males are about 44.3cm (including a 21.5cm tail). Males usually also weigh more than females.

  • Range mass
    230 to 300 g
    8.11 to 10.57 oz
  • Average mass
    275.50 g
    9.71 oz

Reproduction

Reproduction by a male dusky-footed wood rat depends on its proximity to other male conspecifics. In the presence of many male rats, individual male rats may not reach full sexual maturity or physical size. However, when a male wood rat is isolated it immediately increases its weight and becomes sexually mature. At this time, the testes increase in size dramatically.

The reproductive period of this species usually begins in late September and continues until mid-June or mid-July. This coincides with the onset of the rainy season and the growth of plants. The inactive reproductive period arrives in the dry season when much of the vegetation is not growing.

Females also show seasonal changes in reproductive activity. The months of April and May are when most females are reproductively active. Females mate with a single male, and there is no evidence of polygamy. During the breeding season, males move about changing nests in search of sexually receptive females. Males pair with the most accessible female, which is usually the one closest to their nests. The fewer females present in an area, the more a male will move.

Females remain in their original nests and may raise a succession of litters. Some females may experience reoccuring oestrous cycles without becoming pregnant. This occurs when there are fewer males than females in an area, and each of these males limits its attention to a single female. The result is that some females are without a male for a long time.

Once gestation begins, the female is intolerant toward the male and somtimes will attack the male. If a male approaches an intolerant female, and if he has not mated yet, he will leave the vicinity and find another receptive female. Once a male mates, he lives alone in a separate nest which he builds himself. By spring, most females begin producing young. The suckling young, about 2.8 per litter, are dependent to the mother until the time of weaning. Weaning begins three weeks after the young are born. After weaning, the young begin to eat the same greens as their parents. Females protect suckling young by hovering over them and attempting to bite an animal who tries to touch them.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual

Behavior

The dusky-footed wood rat is a nocturnal animal, although some have been observed during the daytime. Individual wood rats vary in the times they become active in the evening. The time of the day, the season of the year, and the weather determine the length of time of activity.

The posture of a wood rat indicates the feeling or mood of an individual of the species. When a dusky-footed wood rat sits quietly but on alert, the hind feet and one or both forefeet bear the weight while one or both forepaws may be raised against the breast with the paw flexed. The tail is sometimes extended over the more or less humped back. When annoyed, angered, or fighting, a dusky-footed wood rat pulls its ears back.

Sometimes males fight when they encounter each other. Usually, one male rushes at the other and bites his opponent. They both beat their tails against the ground and open and shut their mouths. Face washing is characteristically seen following a disturbance, but only when the rat feels safe. Tooth chattering and biting are used against and by intolerant conspecifics.

It is more common, however, for members of this species to be tolerant of one another. Friendliness between individuals, both males and females, is usually seen when they live in adjacent houses.

Locomotion is another behavior studied by scientists. It was found that this species travels equally well through bushes and trees and over ground, as long as the path is free of impediment close to the surface. However, they need a path with overhead cover. When a wood rat travels across leaves, it walks slowly, lifting one leg at a time. In contrast, it will run across branches. This difference in locomotion probably occurs because running across leaves causes a crackling noise which may attract predators.

When a dusky-footed wood rat runs, its tail is normally held straight out behind and parallel with its substratum. It has also been observed that rats use their tails as a warning device against predators.

Although males travel among different houses looking for a mate, they eventually find a mate and live in a permanent residence. As a result, this species has well-developed sanitation habits. Excrement is carefully kept from their homes. Some wastes do accummulate in the house, but they are placed in areas that do not interfere with continuous living in the house.

Dust bathing is a common practice of the dusky-footed wood rat. This process involves spreading the four legs and drawing and pushing the abdomen against the dry soil. After this process, according to one scientists observation, the rats seem to be relaxed. Fecal matter was found in the area, and this may explain why the wood rats push their abdomans against the soil.

Dusky-footed wood rats also lick their pelage for cleanliness. Analyzing the behavior of captive rats has proved to be difficult because only fleeting glimpses are seen of certain spects of behavior. Therefore, many observations of wood-rat behavior have been made on captive wood rats.

Wood rats prefer using trees, branches and limbs to travel. Among trees, the dusky-footed wood rat uses a ground trail or route. These trails eliminate uncertainty about where to go when the wood rat is being pursued by an attacker, and they also provide a quieter path over what could be a litter-strewn area. The trail will not have any obstacles on it, and often represents a straight line connecting two sites of rat activity. These trails are maintained both accidently through use and deliberately.

Communication and Perception

Food Habits

The dusky-footed wood rat feeds on seventy-two different types of plants. Some of these include Blackberry, Maul Oak, Valley Oak, Soap plant, Gold fern, and Bracken. This was determined by analyzing food specimens in homes of dusky-tailed wood rats. The plants consumed by the dusky-footed wood rat are utilized for nutrients as well as their water content. This species derives moisture from eating the vegetation. However, the availibility of certain plants varies with the seasons. This species has a tendency to store a large amount of food in its nests. In one nest, for example, there were one hundred and thirty-two cuttings of fresh material. The dusky-tailed wood rat eats food throughout the night. In one feeding period, they consumed 44.2g on average.

Economic Importance for Humans: Positive

In coastal areas of California, feces from the dusky-footed wood rat can be found in large quantities in the inner base of the rat houses. These feces have be used as garden fertilizer. The commercial use of fertilizer in California has led to the removal of one to three sacks of feces per wood rat nest.

Conservation Status

This species can be found abundantly within its geographgic range. It is not endangered or threatened.

Other Comments

The dusky-footed wood rat and its relatives in the genus Neotoma are sometimes called pack rats, trade rats, bush rats, and cave rats. This species is known to have many animal associates. These associates have been placed into three groups: predators, parasites, and commensals. Predators of this species are skunks, hawks, owls, and wild cats. The wood rat carries parasites such as ticks, mites, and fleas. Many other animals are commensals with the wood rat, using its nest for shelter. The King Snake is one such animal.

Contributors

Christopher Bonadio (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

References

Donat, F. 1935. Notes on the breeding behavior and fertility of Neotoma fuscipes macrotis in captivity. Journal of Mammalogy, 14: 105-109.

Donat, F. 1933. Notes on the life history and behavior of Neotoma fuscipes. Journal of Mammalogy, 14: 19-26.

English, P. 1923. The dusky-footed wood rat(Neotoma fuscipes). Journal of Mammalogy, 4: 1-9.

Howell, A. 1926. Anatomy of the wood rat. Baltimore: The Williams and Wilkins Co..

Linsdale, J., L. Tevis. 1951. The Dusky-footed Wood Rat. Berkeley and Los Angeles: University of California Press.

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