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Sylvilagus nuttalliimountain cottontail

By Alyce Dohring

Geographic Range

The mountain cottontail lives mostly in the western part of the United States. Its range is bordered in the east by Montana’s eastern border, in the west by the Sierra Nevada Mountains, in the south by the middle of New Mexico and Arizona, and in the north by the US/Canadian border; however a small area of Canada right above Montana and Washington is also included. (Chapman, 1975)

Habitat

The cottontail inhabits brushy or wooded areas on slopes or riverbanks that are often covered with grasses, willows, and most importantly, sagebrush. If vegetation is sparse, as on a rocky mountainside, these rabbits can hide in burrows or rock crevices. (Chapman, 1975) (Sibr, online)

Physical Description

The mountain cottontail is of medium to large size for its genus with long hind legs and a large tail that is dark on top and light below. The top of the body is covered in grayish brown fur, and the underbelly is white. The hind legs are covered with reddish brown hairs that are long and dense. The ears are rather short and rounded. They have black tips and long hairs on their inner surfaces. The animal's whiskers are usually white. The females have eight to ten mammae. In this species there is a single annual molt. The rabbits weigh between 0.7 kg and 1.2 kg and are between 35 cm and 39 cm in body length. Females are nearly five percent larger than males.

Skull characteristics of Sylvilagus nuttallii include a long rostrum, small supraorbital processes, and long and slender postorbital processes. The animal also has a rounded braincase, and a dental formula of 2/1, 0/0, 3/2, 3/3 with rather large molariform teeth.

(Chapman, 1975) (Chapman, 1999) (Enature, online) (Schneider, 1990)

  • Range mass
    0.7 to 1.2 kg
    1.54 to 2.64 lb
  • Range length
    35 to 39 cm
    13.78 to 15.35 in

Reproduction

These cottontails are normally solitary unless the habitat can support more than one animal. The animals mate between March and July and almost always at night. They do not form pair bonds. (Chapman, 1975) (Schneider, 1990) (Verts & Gehman, 1991)

The gestation period is 28-30 days and the female can have four or five litters per year. The litter size is usually 4-8 but in California it is not unusual for a litter to consist of just two babies. Female babies are slightly more abundant than male babies (1 male to 1.1 females).
The young are able to move around outside the nest when they weigh about 75 grams and are weaned after only one month. Sexual maturity appears to be at a minimum of 3 months but probably is actually later than that. (Chapman, 1999) (Chapman, 1975)
  • Breeding season
    March-July
  • Range number of offspring
    1 to 8
  • Average number of offspring
    5
  • Average number of offspring
    3.6
    AnAge
  • Range gestation period
    28 to 30 days
  • Range weaning age
    28 (high) days
  • Range age at sexual or reproductive maturity (female)
    90 (low) days
  • Range age at sexual or reproductive maturity (male)
    90 (low) days

Before the female gives birth she makes a nest that is shaped like a cup and lines it with grass, fur, and sticks. The young are altricial with no hair, and they are blind. (Schneider, 1990) (Sibr, online)

Lifespan/Longevity

  • Range lifespan
    Status: captivity
    7.4 (high) years
    AnAge

Behavior

The mountain cottontail is solitary perhaps because food is a limiting factor and shelter in their environment can be sparse. It is active and on the move all year long, looking for areas with an ample food supply. The animal is crepuscular and feeds in or near sheltering brush. Severe weather limits their ability to gather food. Because food and sometimes moisture is sparse, energy is very important. The animal uses less than ten percent of its energy during the reproductive season to mate. After the mating season, males often become more secretive and stealthy. Females, however, are equally active throughout the year.

When the animal is frightened it runs several meters to an area where it can hide and freezes with its ears erect to assess the situation of danger. If the cottontail is further disturbed, it rapidly hops away and tries to trick the predator by running in a semicircular path.

The animal spends more than half of its time, when out in open, feeding. (Chapman, 1975) (Verts & Gehman, 1991) (Sibr, online)

Communication and Perception

Food Habits

The rabbit feeds near water, in the cover of brush, or in the open near brush cover. Heavy wind and rain can reduce the likelihood that the animal will eat in the open. (Chapman, 1975) (Verts & Gehman, 1991)

Mountain cottontail prefer grasses when they are available above other food sources, but when grasses are sparse major foods are sagebrush, Western Juniper and the juniper berries. (Enature, online)

  • Plant Foods
  • leaves
  • fruit

Predation

The only antipredation techniques reported are rapidly running to a safe sheltered area and restricting activity to dusk and dawn.

(Chapman, 1975) (Bull, 2000) (Sibr, online)

Mammalian predators include coyotes, bobcats, and martens. Other predators include hawks, eagles, owls, and rattlesnakes.

Ecosystem Roles

This cottontail eats the grass on mountainsides and keeps the vegetation sparse.

Parasites include nematodes and cestodes.

Economic Importance for Humans: Positive

Their droppings serve as fertilizer and the rabbits are potentially food for endangered species of carnivorous birds, mammals, and snakes. Like other cottontails, the mountain cottontail is valued by humans for its beauty and grace.

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

They graze on grasses until the area is depleted, which can cause habitat change.

Conservation Status

The mountain cottontail is common in its geographic range but has rapidly declined in western North Dakota. (Chapman, 1999)

Other Comments

There are three subspecies of Sylvilagus nuttallii: S. nuttallii grangeri, S. nuttallii nuttallii, S. nuttallii pinetis. Another common name of this animal is Nuttall’s cottontail. (Chapman, 1999)

Contributors

Alyce Dohring (author), University of Michigan-Ann Arbor, Kate Teeter (editor), 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

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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.

chemical

uses smells or other chemicals to communicate

coprophage

an animal that mainly eats the dung of other animals

crepuscular

active at dawn and dusk

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.

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

forest

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

herbivore

An animal that eats mainly plants or parts of plants.

internal fertilization

fertilization takes place within the female's body

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

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

scrub forest

scrub forests develop in areas that experience dry seasons.

sexual

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

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

"Nuttall's Cottontail, sibr.com" (On-line). Accessed November 14, 2001 at http://www.sibr.com/mammals/M046.html.

Bull, E. Summer 2000. Seasonal and sexual differences in American marten diet in northeastern Oregon. Northwest Science, 74(3): 186-191.

Chapman, J. 1999. Smithsonian Book of North American Mammals. Washington, London: Smithsonian Institution Press.

Gordon, C. "Mountain Cottontail, enature.com" (On-line). Accessed November 14, 2001 at http://www.enature.com/guides.

Schneider, E. 1990. Grzimek's Encyclopedia of Mammals, Vol 4. New York: Mc Graw-Hill Publishing Co..

Verts, B., S. Gehman. Nov 1991. Activity and Behavior of Free-living Sylvilagus nuttallii. Northwest science, 65(5): 231-237.

Wilson, , Ruff, J. Chapman. 1975-78. Mammalian Speices 51-100. American Society of Mammalogists.

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