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Cerdocyon thouscrab-eating fox

By Amanda Hover

Geographic Range

The crab-eating fox (Cerdocyon thous) is distributed from Colombia and Venezuela south to Paraguay, Uruguay and Northern Argentina (Eisenberg, 1999).

Habitat

The habitat of C. thous includes mostly savannahs and woodlands, however this species is known to inhabit a variety of other areas including edge and forested areas (Eisenberg, 1999). These foxes may use higher ground during the rainy season, and lowlands during the dry season (Nowak, 1999).

Physical Description

Generally, the crab-eating fox resembles the size and shape of most foxes. The coat is gray-brown on dorsally, with the face, ears, and legs reddish. The throat and underside of C. thous is white. The tips of the ears, tail, and legs are black. C. thous has short, robust legs. The head and body length averages 643 mm and the average tail length is 285 mm (Berta, 1982). These foxes weigh between five and eight kg.

  • Range mass
    5 to 8 kg
    11.01 to 17.62 lb
  • Average length
    643 mm
    25.31 in
  • Average basal metabolic rate
    8.502 W
    AnAge

Development

See Reproduction.

Reproduction

Captive crab-eating foxes are monogamous and often breed twice per year in intervals of 7 to 8 months with a possible peak in births during January or February (Berta, 1982).

Breeding in C. thous takes place throughout the year, but peaks November or December (Canid Specialist Group, 1998). The gestation period of C. thous averages 56 days, leading to a peak of births in January and February (Nowak, 1999). Females produce between 3 and 6 pups per litter (Medel, 1988). Captive females have been known to reproduce twice annually, although information for wild crab-eting foxes is not available. At birth, C. thous pups weigh between 120 and 160 grams. They are born without teeth, and their eyes and ears closed (Berta, 1982). The eyes of the newborns open at 14 days, and they start digesting solid food at 30 days. Pups are weaned at 90 days (Nowak, 1999). The pups' coats are charcoal grey with a yellowish-brown patch on the lower abdomen. Twenty days after birth the pelage starts to change, and by the 35th day pups show adult pelage (Berta, 1982). Sexual maturity is reached by the first year. Raised leg urination (in both sexes) is indicative of sexual maturity in C. thous (Berta,1982; Medel, 1988).

  • Breeding season
    Peak breeding occurs in November and December.
  • Range number of offspring
    3 to 6
  • Average number of offspring
    4
  • Average number of offspring
    4
    AnAge
  • Range gestation period
    52 to 59 days
  • Average gestation period
    56 days
  • Average weaning age
    90 days
  • Average age at sexual or reproductive maturity (female)
    9 months
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    274 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    9 months
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    274 days
    AnAge

The female nurses the young for about 90 days. When solid food is ingested (around 30 days) both parents bring the young food. Both parents guard the young (Nowak, 1999).

Lifespan/Longevity

In captivity the crab-eating fox has been known to live up to eleven years six months (Nowak, 1999).

Behavior

The crab-eating fox is nocturnal and lives in monogamous pairs (Eisenberg, 1999). They travel in pairs but hunt individually (Berta, 1982). Their home range varies between 0.6 to 0.9 km2 (Eisenberg, 1999). During the dry season, they tend to be more territorial than during the wet season, however overlap of territories is common (Nowak, 1995).

Communication and Perception

Food Habits

The crab-eating fox is omnivorous. In one study their diet included 25.3% small mammals, 24.1% reptiles, 0.6% marsupials, 0.6% rabbits, 10.3% birds, 35.1% amphibians, and 5.2% fish (Medel, 1988). However, in other studies (see Berta, 1982) the porportion of animals consumed is different, suggesting an opportunistic feeding behavior, and they may shift their food habits seasonally. During the wet season in the low llanos, crabs and other crustaceans are consumed, whereas during the dry season their diet contained more insects (Berta, 1982).

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • fish
  • insects
  • terrestrial non-insect arthropods
  • aquatic crustaceans

Predation

Predation upon this species has not been reported.

Ecosystem Roles

Because of its role as a predator, C. thous may help to control populations of small mammals, insects, fish, and crabs.

Economic Importance for Humans: Positive

Although the pelt is worth little, the crab-eating fox is hunted intensively (Berta, 1982).

Economic Importance for Humans: Negative

There is little evidence that C. thous impacts the local livestock, however the animal is often shot by local farmers and ranchers (Canid Specialist Group, 1995).

Conservation Status

C. thous is listed in CITES Appendix II (CITES, 2000), but the Argentine Wildlife board has declared the crab-eating fox out of danger (Canid Specialist Group, 1998).

Other Comments

C. thous was formerly known as Dusicyon thous. C. thous is a monotypic species but formerly the subgenera Atelocynus and Speothos were included in Cerdocyon.

Cerdocyon thous is derived from three Greek words kerdo (fox), cyon (dog) and thoos (jackel). The word 'zorro' is spanish for fox. Other common names include Zorro del Monte, Azara's Fox and Zorro Perro (Berta,1982; Canid Specialist Group, 1998).

Contributors

Amanda Hover (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor), University of Wisconsin-Stevens Point.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

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.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

forest

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

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

monogamous

Having one mate at a time.

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.

nocturnal

active during the night

sedentary

remains in the same area

sexual

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

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

viviparous

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

year-round breeding

breeding takes place throughout the year

References

Berta, A. 1982. *Cerdocyon thous*. Mammalian Species, No: 186: 1-4.

CITES, 2000. "Appendices I and II" (On-line). Accessed October 24, 2001 at http://www.cites.org/eng/append/appendice12.shtml.

Canid Specialist Group, 1998. "Crab-eating Zorro (*Cerdocyon thous*)" (On-line). Accessed August 27, 2001 at http://www.canids.org/SPPACCTS/cthous.htm.

Eisenberg, J., K. Redford. 1999. Mammals of the Neotropics: the Central Neotropics. Volume 3.. Chicago, IL: University of Chicago Press.

Medel, R., F. Jaksic. 1988. Ecología de los c·nidos sudamericanos: una revisiόn. Revista Chilena de Historia Natural, 61: 67-79.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore and London: John Hopkins University Press.

Nowak, R. 1995. "Crab-eating Fox" (On-line). Accessed October 24, 2001 at http://www.press.jhu.edu/books/walker/carnivora.canidae.cerdocyon.html.

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