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).
Biogeographic Regions:
neotropical 
(native ).
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).
These animals are found in the following types of habitat:
tropical .
Terrestrial Biomes:
forest .
Physical Description
(11 to 17.6 lbs)
(25.31 in)
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.
Some key physical features:
endothermic ; homoiothermic; bilateral symmetry .
Reproduction
Peak breeding occurs in November and December.
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).
Mating systems:
monogamous .
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).
Key reproductive features:
iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (internal ); viviparous .
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).
Parental investment:
altricial ; male parental care ; female parental care .
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).
Key behaviors:
nocturnal ; crepuscular ; motile ; sedentary ; territorial ; social .
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).
Primary Diet:
carnivore (eats terrestrial vertebrates, insectivore , eats non-insect arthropods).
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: 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).
Economic Importance for Humans: Positive
Although the pelt is worth little, the crab-eating fox is hunted intensively (Berta, 1982).
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).
For More Information
Find Cerdocyon thous information at
Contributors
Amanda Hover (author), University of Wisconsin-Stevens Point.
Chris Yahnke (editor), University of Wisconsin Stevens Point.
