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Sylvilagus graysoniTres Marias cottontail

By Lata Viswanathan

Geographic Range

Sylvilagus graysoni is restricted to the Tres Marias Islands, 100 km west of the coast of Mexico.(Nowak, 1999)

Habitat

The habitat of Sylvilagus graysoni consists of dense vegetation, including trees and bushes. This species thrives in areas that provide cover, and does not prefer to be in open fields.

These rabbits seek shelter in burrows made by other animals, under piles of brush, or within the vegetation. (Schneider, 1990)

Physical Description

The Tres Marias cottontail is a medium to large-sized rabbit, with gray, brown, and red fur. Its underside is generally pale brownish-red, and the species is characterized by a brown patch of fur on its throat. Its tail is brown above and white below. These rabbits do not turn white during the winter.

The average head and body length ranges from 215-471 millimeters, while tail length varies from 15-60 millimeters. Compared to other species of cottontails, Sylvilagus graysoni has relatively short ears that are approximately 57 millimeters long. The average length of the rabbit's hind foot is 95 millimeters.

Females in the species have four or five pairs of mammae. There are no significant sexual dimorphism except that adult females tend to be slightly larger than adult males. (Cervantes, 1997; Schneider, 1990)

  • Range mass
    0.24 to 2.7 kg
    0.53 to 5.95 lb
  • Average mass
    1.47 kg
    3.24 lb

Reproduction

There is very little information on the reproduction of this species. The gestation period, number of young per birth, and number of litters per lifetime are unknown.

There is no mention of when in the year births are most likely to occur, the degree of development of the neonate, or the weight and length of the newborn rabbit.

There is no information regarding the estrous cycle of females, or of the mating systems of Tres Marias cottontails. (Cervantes, 1997; Nowak, 1999; Schneider, 1990)

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

Behavior

Tres Marias cottontails are generally nocturnal, but are often seen during the daytime also. They are almost exclusively terrestrial, and are active throughout the year. This species of cottontails moves around using a characteristic "bunny hop."

It is not known whether these rabbits are a social or a solitary species. However, it is known that during breeding season, several males pursue estrous females together.

Females excavate a special protective shelter for the sake of rearing their young. The mother digs a hole approximately 150 millimeters deep and 120 millimeters wide. She then lines it with soft plants and fur from her underside. This nest is to ensure that the baby rabbits stay warm and safe. The female sits above the hole (not in it), and the newborns climb to the top to feed on her milk.

Tres Marias cottontails are able to protect themselves through their ability to remain almost completely still and silent for up to 15 minutes. This adaptive trait enables them to be undetected even when closely approached.

(Nowak, 1999; Schneider, 1990)

Communication and Perception

Food Habits

Tres Marias cottontails feed on a wide variety of plant material and herbaceous species. Their diet consists of bark and twigs during the colder months of the year.

This species, like other rabbits, excrete two kinds of fecal matter. The soft, green pellets are reingested in order to absorb vitamin B that can only be extracted after food is digested once. (Nowak, 1999; Schneider, 1990)

Economic Importance for Humans: Positive

Tres Marias cottontails are hunted by humans. They benefit humans by providing game for hunters and valuable furs. (Cervantes, 1997; Nowak, 1999)

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

Economic Importance for Humans: Negative

There is no evidence of Tres Marias cottontails adversely affecting humans. There is documentation of other species of cottontail rabbits damaging crops, forest plantations, and shrubs.

(Nowak 1999; Schneider, 1990)

Conservation Status

Sylvilagus graysoni flourished throughout the Tres Marias Islands at the beginning of the century, but in the last survey of this species (1976) it was shown that its population has significantly dropped. In the last 10 years, the number of Sylvilagus graysoni has been reduced by 50 percent. This trend is anticipated to continue.

This species has evolved in an environment that is relatively predator-free, and therefore it is not prone to run away if approached by humans. Hunters kill these rabbits with minimal difficulty. Other threats to its survival include modification of its habitat by clearing of vegetation, newly introduced species such as pigs and goats, and human settlements.

Surveys have been recommended to determine the present status of the species. Research is being initiated with hopes of preserving the remainder of the species. (Cervantes, 1997; Hoffman, 1993)

Contributors

Lata Viswanathan (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

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

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.

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.

island endemic

animals that live only on an island or set of islands.

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.

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

tactile

uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Cervantes, F. 1997. Sylvilagus graysoni. Mammalian Species, 559: 1-3.

Hoffmann, R. 1993. Mammal Species of the World: A Taxonomic and Geographic Reference, Second Edition. Washington: Smithsonian Institution Press.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition; Volume 2. Baltimore: The John's Hopkins University Press.

Schneider, E. 1990. Grzimek's Encyclopedia of Mammals; Volume 4. New York: McGraw-Hill Publishing Company.

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