Crab-Eating Fox

The crab-eating fox is extremely adaptable, living in all sorts of habitats and eating almost any available food!

Based on its name, you might think the crab-eating fox eats only crabs. That assumption would be wrong. This South American fox is actually one of the most adaptable canids. It is an omnivore, and quite the opportunist, eating whatever is most readily available at any given time throughout its range. In the rainy season, foxes living near muddy floodplains do indeed eat a lot of crabs. But during other seasons, or in other locations, they are much more likely to prey on mammals, reptiles, birds, fish, or other invertebrates. These gray-brown foxes with black markings are mostly active at night, and travel in monogamous pairs. Their population is considered stable, but their greatest threats come from human activity.

Incredible Crab-eating Fox Facts

• The crab-eating fox eats a lot more than just crabs, including grasses and fruits.
• These foxes form monogamous pairs that care for their cubs equally.
• No one knows how many crab-eating foxes exist.
• There are five recognized subspecies that range across much of South America.
• The pelts of crab-eating foxes are too short and coarse to make them desirable for fashion.
• This species is sometimes called the forest fox, savanna fox, wood fox, bushdog, common zorro, common fox, or maikong.

Where to Find Crab-eating Foxes

Crab-eating foxes are native to South America. They inhabit much of Colombia and Venezuela, and parts of Ecuador, Guyana, and Suriname in the northern part of the continent. They are also found in Brazil, mainly along the coast and to the south of the Amazon basin. Their range extends west into Bolivia and Paraguay, and south throughout Uruguay and the northern part of Argentina. There is also some indication that these foxes may be found in French Guiana.

The crab-eating fox is a highly adaptable species. These foxes make use of many types of habitats within their range, and they adapt well to disruptions in their habitat. They may be found in montane forests, along the coasts, in marshlands and in tropical and subtropical savannas. They also inhabit desert-like shrublands such as the Caatinga and the dry and mostly uninhabited Gran Chaco region.

Areas of agricultural development and deforestation don’t seem to bother crab-eating foxes. They are found frequently around areas used for livestock or crops. They tend to move between elevations to avoid floods, moving to higher ground during the rainy seasons and returning to low-lying habitat during the dry seasons. Thanks to their highly varied diet, they are able to adapt to almost any sort of habitat within their range, and although they don’t seem to migrate seasonally, the species does seem to be expanding its range over time.

Scientific Name

The crab-eating fox is known by many names. It is sometimes called the forest fox, savanna fox, wood fox, bushdog, common zorro, common fox, or maikong. Its scientific name is Cerdocyon thous, which is derived from Greek words meaning fox and dog. It is the only living species in the Cerdocyon genus, named by Charles Hamilton Smith, a British soldier, spy and naturalist, in 1839. The crab-eating fox had previously been named Canis thous by Linnaeus in 1766.

Today, there are five recognized subspecies of crab-eating foxes. There are differences in coat colors and size, and the various subspecies range over different parts of South America. The nominate subspecies, C. t. thous, lives in Venezuela, Guyana, Suriname, northern Brazil and perhaps French Guiana, although the recorded sightings in that country have not been confirmed. The other northernmost subspecies, C. t. aquilus, ranges through northern Venezuela and Colombia. The subspecies with the smallest range, C. t. germanus, lives only in the Bogotá region of Colombia. Meanwhile, C. t. azarae ranges in northern Brazil while C. t. entrerianus is found further south, in Brazil, Bolivia, Uruguay, Paraguay and Argentina.

Appearance

The crab-eating fox is similar in size and shape to more familiar foxes. It has a long, bushy, mostly black tail. Its large ears are pointy, but more rounded than many other canids. They are also tipped in black. Its snout is pointed, but a bit shorter than similar canids. Its legs are relatively short, compared to other members of the Canidae family, and the lower portions are black. Crab-eating foxes have a gray-brown coat with white undersides. Their coats vary from dark to lighter in shade, often tinged with red around the face, ears and upper legs. Except for the tail, their fur is short and coarse.

These foxes average about 22 to 30 inches from nose to rump. Their tails add close to another foot to their length. They weigh between 10 and 18 pounds. This is very close to the size of the familiar red fox, Vulpes vulpes, found throughout much of the northern hemisphere and in Australia. The crab-eating fox is also virtually the same size as the pampas fox, Lycalopex gymnocercus, which shares much of its southern range. The pampas fox, however, is lighter in color, has a longer snout, and lacks the black tips on its ears and black legs.

Behavior

Crab-eating foxes are mostly nocturnal and crepuscular in nature. According to one study, they were most active in the early half of the night, before midnight, and again in the hours close to dawn. They appeared to share the same habitat with the similar pampas fox by dividing the hours of each day in shifts, with the pampas fox being more active in the late-night hours between about midnight and 4:00 am, and again during the daylight hours.

Crab-eating foxes generally form monogamous pairs that inhabit a relatively small territory, smaller than five square miles. The pairs travel together over their territory, sometimes accompanied by their offspring, but they tend to hunt alone. They communicate through high pitched barks that can be heard over long distances. The territories of rivals may overlap, and if food is abundant interlopers may be tolerated. However, crab-eating foxes have been observed aggressively defending their territory against others, particularly during the dry season.

These foxes spend most of the day resting. They usually find places to rest above ground, within dense cover if they are in the midst of raising a litter. They do not excavate their own burrows like some other foxes. However, they do sometimes utilize holes made by other animals, such as the armadillos that are common within their range.

Diet

Contrary to the name of this species, the omnivorous crab-eating fox eats much more than just crabs. In fact, the diet of Cerdocyon thous is quite varied and these foxes tend to favor whatever food is most readily available. Grasses constitute a large portion of their diet, and according to research may be necessary to aid in their digestion of other foods. These foxes also frequently consume fruits, such as murici, mess apples, and gooseberries. They may be instrumental in dispersing the seeds of these plants within their range.

In addition to vegetation, crab-eating foxes consume a wide variety of different animals and even insects, although these may be ingested accidentally when individuals eat infested fruits or carrion.

Although the crab-eating fox does hunt for land crabs and other crustaceans in low-lying flood plains during the rainy season, crabs are not always the most significant part of their diet. These foxes are highly opportunistic feeders and will eat almost any type of small animal. They eat mammals, including rodents, opossums, and armadillos. They eat reptiles, including lizards, snakes and tortoises. Amphibians and fish often make the menu, as well as birds and their eggs. Invertebrates of all sorts, carrion, and even human garbage are regular parts of the crab-eating fox’s diet.

Reproduction

Crab-eating foxes form monogamous pairs that live and travel together across a relatively small territory. In the wild, pairs have one litter per year, although they may have up to two litters per year in captivity. Their offspring are usually called cubs, but they may be referred to as kits or pups.

These foxes have between two to six cubs per litter. The cubs are born after a gestation period of 56 days. Both parents care for the cubs together, bringing them whole prey after they reach about 16 to 20 days old. The cubs are weaned after about 90 days, but stay with the parents for many months after that, until they are between 18 and 24 months old. They may even return to live in the same vicinity as their parents if their presence is well tolerated.  

Predators & Threats

Adult crab-eating foxes have no common predators. Human activity is the greatest threat to these foxes, primarily through the introduction of diseases via domestic dogs. Dogs and crab-eating foxes frequent the same food sources, garbage dumps created by humans. At these feeding locations, dangerous introduced pathogens are spread to the wild foxes.

Persecution by humans is another threat to crab-eating foxes who wander too near livestock. These foxes are known to take chickens, eggs, and possibly lambs, and humans often retaliate by killing the foxes. Although hunting of wildlife is illegal in many areas, and quotas exist in others to prevent overharvesting, limits and restrictions are often ignored.

Lifespan

The IUCN Red List for Threatened Species lists the crab-eating fox as a species of least concern. Although the exact population is not known, based on surveys, researchers believe that the population is stable across its range. The lifespan of this fox in the wild is not known, but in captivity it has been recorded at 11.5 years. There are currently no conservation plans in place for the crab-eating fox, but its commercial trade and use is prohibited by law.  

1. Canids: Foxes, Wolves, Jackals and Dogs, Available here: https://www.carnivoreconservation.org/files/actionplans/canids.pdf
2. Journal of Mammalogy/Mario S. Di Bitetti, et. al., Available here: https://academic.oup.com/jmammal/article/90/2/479/900072
3. Brazilian Journal of Biology/F. M. Dutra-Vieira, et. al., Available here: https://www.scielo.br/j/bjb/a/TPBQFkVCJNxcpGHRKXkT5Ht/?lang=en
4. IUCN Redlist, Available here: https://www.iucnredlist.org/species/4248/81266293#conservation-actions