Canidae Author Don E. Wilson Author Russell A. Mittermeier text 2009 2009-01-31 Lynx Edicions Barcelona Handbook of the Mammals of the World – Volume 1 Carnivores 352 446 book chapter http://doi.org/10.5281/zenodo.6331155 978-84-96553-49-1 6331155 12. Crab-eating Fox Cerdocyon thous French: Renard crabier / German: Savannenfuchs / Spanish: Zorro cangrejero Other common names: Savannah Fox Taxonomy. Canis thous Linnaeus, 1766 . Suriname . Five subspecies are recognized. Subspecies and Distribution. C. t. thous Linnaeus, 1766 — N Brazil , the Guianas, and SE Venezuela . C. t. aquilus Bangs, 1898 — N Colombia , N Venezuela . C. t. azarae Wied-Neuwied, 1824 — NE & C Brazil . C. t. entrerianus Burmeister, 1861 — Argentina , Bolivia , S Brazil , Paraguay , and Uruguay . C. t. germanus G. M. Allen, 1923 — Colombia ( Bogota region ). Descriptive notes. Head-body 57-775 cm and tail 22-41 cm ; weight 4-5-8-5 kg . Mediums-sized, tail moderately bushy, often with black tip and dark at base. No sexual dimorphism. Rostrum long and pointed, head relatively short and narrow. Pelage generally dark gray to black along dorsum down to midline; midline to ventrum including legs gray or black, sometimes with yellow to orange flecks; neck and underparts cream to buff white. Pelage notably bristly and coarse. Substantial inter- and intra-population pelage color variation including dark to almost black (e.g. northern Venezuela , Amazonia, central Brazil ), silver gray (e.g. Venezuelan Llanos), and pale gray-yellow rufous (e.g. Ceara , Brazil ). Continuous black dorsal line from neck to tail tip variably present. The dental formulais13/3,C1/1,PM 4/4, M 1/2 = 44. Habitat. Occupies most habitats including marshland, savannah, cerrado, caatinga, chaco-cerrado-caatinga transitions, scrubland, woodlands, dry and semi-deciduous forests, gallery forest, Atlantic forest, Araucaria forest, isolated savannah within lowland Amazon forest, and montane forest. Records up to 3000 m . Readily adapts to deforestation, agricultural and horticultural development(e.g. sugarcane, eucalyptus, melon, pineapples), and habitats in regeneration. In the arid Chaco regions of Bolivia , Paraguay , and Argentina , confined to woodland edge. Vegetative habitats generally utilized in proportion to abundance, varying with individual fox’s social status and climatic season. Radio-tagged foxes in seasonally flooded savannas of Marajo, Brazil , preferred wooded savannah and regenerating scrub. In the central Llanos of Venezuela , fox home ranges were generally located in open palm savannah (68% of sightings) and closed habitats (shrub, woodlands, deciduous forest, 32% of sightings). The foxes shifted to higher ground in response to seasonal flooding. In Minas Gerais , Brazil , two radio-tagged foxes were observed most often at the interface of livestock pasture and gallery forest “vereidas” and less frequently in eucalyptus/agricultural plantations (8%). Food and Feeding. Omnivorous: diet includes fruit, vertebrates, insects, amphibians, crustaceans, birds, and carrion. An opportunistic predator; diet at any one location varies according to availability, season, and probably social status. In areas of human disturbance, a large proportion of the diet may comprise foods such as cultivated fruits, domestic fowl, and refuse. In the Venezuelan Llanos, the percent volume of food items from the contents of 104 fox stomachs from four different locations included: small mammals (26%), fruit (24%), amphibians (13%), insects (11%); the dry season diet was predominantly small mammals, reptiles, and amphibians, with insect and fruit becoming more frequent in the wet season. In one Venezuelan location, land crabs (Dilocarcinus spp.) were the most frequently occurring dietary item in the rainy season, and in the Ibera Wetlands ( Corrientes , Argentina ), aquatic birds were identified in 87% of 23 fox scats collected in the vicinity of a bird breeding colony. Vertebrates were the most frequently encountered food item (69%) of 74 prey items identified in 22 scats collected at elevations of above 2600 m in the eastern Colombian Andes, but were the least favored food item (15%) in feces collected from the lowland wooded savannahs of Marajo ( Brazil ), where cultivated and wild fruit (57%) and insects (86%) were more frequently encountered. Crab-eating Foxes hunt individually, but most commonly as pairs; 1-3 adultsized offspring may accompany them. Cooperative hunting apparently is rare. They will tolerate close proximity when foraging on concentrated, easily available food items such as turtle eggs, fruit, insects (e.g. termites), and sizeable carrion (e.g. goat carcass). The young start to hunt with the parents at about six weeks of age. Hunting strategies include spring-pouncing to capture vertebrates, ground-level lateral head movements to snatch insects, and directional maneuvers in pursuit of land crabs. The foxes in Marajo deliver a series of shoulder blows, with face up-turned, to some food items (e.g. toads, eggs) prior to comsuming them. In the same region, foxes search for and consume small stones from specific open gravel sites, presumably as a source of minerals. Foxes cache food items but do not regularly urine-mark them. They probably act as seed dispersers of a range of wild and cultivated plant species, as indicated by the presence of germinating seeds in their scats. Examples include Acacia aroma and Celtis tala (montane Chaco , Argentina ), Butia capitata ( Uruguay ), Hovenia dulcis (Iguacu National Park, Brazil ), Ficus spp. (south-eastern Brazil ), Psidium guineense, Humiria balsamifera, and Anacardium occidentale (Amazonian Brazil ). Activity patterns. Primarily nocturnal and crepuscular. Movements, Home range and Social organization. Social groups comprise a breeding pair and 1-5 offspring (older than one year). Family members usually travel around their home ranges in pairs or,if offspring are present, in loosely knit family groups. Separated foxes maintain contact by long distance, high-pitched, bird-like trill vocalizations. In Marajo, Brazil , territorial breeding pairs were located less than 100 m apart on a mean 54% (n = 7) of occasions during the period of activity, whereas close proximity of breeding adults and their adultsized offspring varied from 7-2% to 93-3% between given pairings. In Marajo, Brazil adult foxes occupied stable territories of 5- 3 km ? (range 0-5-10- 4 km ?), whereas in pasture/eucalyptus habitats in Minas Gerais ( Brazil ), an adult male’s range was 2- 2 km ? In dry forest sites in Santa Cruz , Bolivia an adult female and two adult males occupied mean home ranges of 2- 2 km * (range 1-1-2- 8 km ?). In the central Venezuelan Llanos, three adult foxes and three adult fox pairs showed dry season home ranges (mean 0-7 km ?*range 0-5- 1 km ?) to be generally larger than wet season home ranges (mean 0-7 km ? range 0-3- 1 km ?). Shrinkage of fox range sizes in the wet season is thought to be in response to changes in the availability of dry habitats and/or prey density. Dispersing offspring established territories adjoining their natal range. The average distance between range centers was 2-4 km (range 1-9- 2-9 km ). After dispersal, these foxes interacted amicably with kin members both inside and outside their natal ranges. Four male foxes returned to their natal range 3-13 months after their dispersal, in two cases following the death of their mate and in one case after breeding. Group latrines are not usual features of Crab-eating Fox society; however, a latrine comprising over 72 scats visited by at least four adultsized individuals was observed in Maraca Ecological Station, Brazil . The use of scat latrines located near resting sites has also been reported. Breeding. In the wild, litters are produced once per breeding year. Litters were observed in Brazil in the months ofJune to December. In the Venezuelan Llanos,litters were recorded between December and February and lactating females were seen in June. Elsewhere in Venezuela litters were observed year round (January, May, July, and October), and lactating foxes were recorded in August. On emergence from the natal den at 2-3 months, the mean littersize is 2:6 (range 2-3). It is not known whether the presence of a dominant female inhibits ovulation in subordinate females. In captivity, births have been recorded in January, February, March, June, and October, and foxes may breed twice annually at intervals of 7-8 months. Gestation period is 56 days (range 52-59 days), and neonatal weight is 120-160 g . Cub rearing is the responsibility of both breeding adults. Additional helpers have not been observed directly in the wild. However, the strong social affiliations between adults and dispersed returning offspring during subsequent breeding periods are strongly suggestive ofsibling helpers. In captivity, both sexes bring solid food (they do not regurgitate) to the young who consume solids from day 16-20. Pups first leave the den around day 28, but more regularly from day 45, at which time they develop the adult pelage. Lactation lasts for approximately 90 days. Post-weaning dependency lasts for up to five months, until sexual maturity, which occurs at approximately nine months. Offspring disperse when they are 18-24 months old. Crab-eating Foxes do not regularly excavate burrows, but rest aboveground in dense undergrowth (including when rearing pups), and also occasionally adopt abandoned burrows of other animals such as armadillos ( Dasypodidae spp.). Status and Conservation. CITES Appendix II. Classified as Least Concern on The [UCN Red List. Crab-eating Foxes are considered common in most range countries, and populations are probably stable. The species is currently listed as “potentially vulnerable” in the Argentine Red Data Book, but not listed as threatened in Bolivia , Brazil , and Colombia . There is little documentation for populations in Suriname , French Guiana, and peripheral areas of lowland Amazon forest. No specific protective legislation exists for this species, though hunting wildlife is officially forbidden in most range countries. Crab-eating Foxes are potentially threatened by pathogens from domestic dogs. The Crab-eating Fox is also perceived as a pest of poultry throughout much ofits range (and in Uruguay as a predator of lambs), and consequently is often shot, trapped, and poisoned indiscriminately. In some countries, pest control is limited by specific quotas (without official bounties), although the system is often ignored, abused, or not enforced. Trapping occurred extensively in dry forest regions in Bolivia before the early 1980s, when single pelts were worth US $ 30, but the species currently has little commercial value as a furbearer. Crab-eating Foxes are also often killed by vehicles on roadways in some areas. Bibliography. Biben (1982, 1983), Bisbal (1988), Bisbal & Ojasti (1980), Brady (1978, 1979), Cabrera (1931, 1958), Cordero-Rodriguez & Nassar (1999), Courtenay (1998), Courtenay & Maffei (2004), Courtenay, Macdonald et al. (1994), Courtenay, Quinnell & Chalmers (2001), Courtenay, Quinnell, Garcez & Dye (2002), Courtenay, Santana et al. (1996), Cravino, Calvar, Berruti et al. (1997), Cravino, Calvar, Poetti et al. (2000), Eisenberg et al. (1979), Facure & Monteiro-Filho (1996), Hill et al. (1997), Macdonald & Courtenay (1996), Maffei & Taber (2003), Montgomery & Lubin (1978), Motta-Junior et al. (1994), Parera (1996), Paz et al. (1995), Sunquist et al. (1989).