By Travis Cooper
Geographic Range
Lycalopex gymnocercus, pampas foxes, are found in Paraguay, Uruguay, southern Brazil, eastern Bolivia and north of Rio Negro in Argentina. (Wilson and Reeder, 1993)
Biogeographic Regions:
neotropical 
(native ).
Habitat
These foxes are found in the pampas grasslands, hills, heath, ridges and deserts. They prefer plains and fields with tall grass, sierras, and small narrow wood areas along streams and occasionally forest areas. (Brooks, 1992)
Terrestrial Biomes:
desert or dune ; forest .
Physical Description
(9.24 to 14.3 lbs; avg. 11.77 lbs)
(24.41 in)
Lycalopex gymnocercus is a medium-sized fox which has a brindled grey back with paler grey underparts. The head, neck and large ears are reddish, as are the outsides of the legs. The muzzle is black as far as the corners of the mouth, a feature that distinguishes them from the similar culpeo fox (Lycalopex culpaeus). Like other species in the genus, the long, bushy tail of L. gymnocercus has two black spots: one on the upper side at the base and another at the tip. These animals weigh between 4.2 and 6.5 kg, and average 62 cm in length. The tail length for Pampas Foxes averages about 34 cm. Males are approximately 10% heavier than females. Those animals in the northern part of their range are more vividly colored. (Boccaceci, 1998)
Some key physical features:
endothermic ; homoiothermic; bilateral symmetry .
Sexual dimorphism: male larger.
Reproduction
Breeding occurs once yearly.
Mating occurs between July and October.
This species is monogamous. It is not known whether these foxes retain the same mate in subsequent breeding seasons, as they are solitary outside of the breeding season.
Mating systems:
monogamous .
Pampas foxes are usually solitary, but are seen in pairs during the mating season. Breeding is monogamous and occurs from July through October. Both parents care for the young. Gestation lasts from 55-60 days. Females bear three to five pups in a den among rocks, under bases of trees or in burrows made by other animals. Young are born almost black but gradually lighten as they grow. At two to three months, the young begin to hunt with their parents. Age at maturity is unknown. The male pampas fox brings food to the female and her pups, who stay within the den until the pups are about three months old. At this time, the pups begin to hunt with their parents. (Alderton and Sept. 10, 2001)
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous .
Females nurse the pups in the den. The male will provide food for the altricial pups and females at the den. Young stay at the den for the first three months, after which they hunt with parents. (Alderton and Sept. 10, 2001)
Parental investment:
altricial ; pre-fertilization (provisioning, protecting: female); pre-hatching/birth (provisioning: female, protecting: female); pre-weaning/fledging (provisioning: female, protecting: male); pre-independence (provisioning: male, female, protecting: male, female).
Lifespan/Longevity
Pampas foxes live about 13.6 years in captivity. (Grambo, 1995)
Behavior
Pampas foxes have a relatively solitary lifestyle, except during the breeding season and when caring for their young. They exhibit two particularly interesting behaviors. They are known to collect objects which apprear mostly useless to them, such as bits of cloth and leather, which are often found in their dens. They also appear to play dead when approached by humans. If they are startled, these foxes will throw themselves to the ground, rigid, with their eyes closed, and remain in this position until the perceived threat passes. Although primarily nocturnal, they may be active during day in areas with low human populations. (Boccaceci, 1998)
Food Habits
Lycalopex gymnocercus is omnivorous, but primarily eats meat. Approximately 75% of the diet is comprised of equal percentages of rodents, lagomorphs (rabbits, hares, and pikas), and birds. These foxes are known to eat frogs and lizards. Fruits and other vegetable matter, like sugar cane stalks, are sometimes consumed. Near human dwellings they are said to take domestic poultry. (Berta, 1988)
Primary Diet:
omnivore .
Animal Foods:
birds; mammals; amphibians; reptiles.
Plant Foods:
fruit.
Predation
- humans (Homo sapiens)
Information on predation is not available. Humans frequently hunt these foxes, thinking that they destroy livestock. The pampas fox may fall prey to eagles or larger carnivores. Lycalopex gymnocercus individuals remain motionless when humans make an appearance, and may continue to remain motionless if physically molested. This may be an antipredator behavior in which the fox tries to avoid being eaten by pretending not to be there at all. (Grambo, 1995; Nowak, 1999)
Ecosystem Roles
The decline in L. gymnocercus populations has had an adverse affect on agriculture in parts of their range due to increases in rodents and other crop pests. It can reasonably be inferred from this that fox predation plays an important role in regulating the populations of prey animals. (Boccaceci, 1998)
Economic Importance for Humans: Negative
Sometimes these foxes kill young sheep or take domestic poultry. (Alderton and Sept. 10, 2001)
Ways that these animals might be a problem for humans:
household pest.
Economic Importance for Humans: Positive
These foxes are hunted and trapped for fur in several countries, including Uruguay, Paraguay, and Argentina. They are captured most often with leg-hold traps, but also caught using bowls, box traps, and dogs. Because these foxes keep agricultural pest populations in check, they have a positive impact on agriculture. (Grambo, 1995)
Ways that people benefit from these animals:
body parts are source of valuable material; controls pest population.
Conservation Status
IUCN Red List: [link]:
Least Concern.
US Federal List: [link]:
No special status.
CITES: [link]:
Appendix II; Appendix III.
In Brazil, where the species enjoys complete protection, there is no market for fur. Pampas foxes are protected in Paraguay and Uruguay, but controlled hunting continues in these two countries. (Boccaceci, 1998)
Other Comments
These foxes were previously recognized in the genera Pseudalopex and Dusicyon. (Alderton and Sept. 10, 2001; Berta, 1988)
Contributors
Travis Cooper (author), University of Wisconsin-Stevens Point.
Chris Yahnke (editor), University of Wisconsin Stevens Point.
