Pseudalopex fulvipes (Martin, 1837) Burmeister, 1856

Don E. Wilson & Russell A. Mittermeier, 2009, Canidae, Handbook of the Mammals of the World – Volume 1 Carnivores, Barcelona: Lynx Edicions, pp. 352-446 : 429-430

15.

Darwin’s Fox

Pseudalopex fulvipes

French: Renard de Darwin / German: Darwin-Fuchs / Spanish: Zorro chilote

Taxonomy. Vulpes fulvipes Martin, 1837 ,

Chile.

Known until recently only from the Island of Chiloé, Chile. Taxonomic status previously uncertain and confusing; was considered to be an island form of the South American Gray Fox ( P griseus ). However, the discovery of a mainland population in sympatry with the South American Gray Fox and the analysis of mitochondrial DNA of the three Chilean foxes (including P. culpaeus ), provides strong evidence for considering the Darwin’s Fox as a legitimate species. It is now accepted that current populations of Darwin's Fox are relicts of a former, more widely distributed species. Similarities in pelage coloration between P. fulvipes and P. sechurae from the coastal desert of Peru (2000 km to the north) support speculations of a phylogenetic relationship between these two species. Monotypic.

Distribution. Endemic to Chile, with a disjunct distribution in the forests of Chiloé Island, and on the mainland coastal mountains in Nahuelbuta National Park. Evidence of a new population was foud recently at Punta Chan Chan, N of Valdivia.

Descriptive notes. Head-body 48-2-56- 1 cm for males and 48-59- 1 cm for females, tail 19-5-25- 5 cm for males and 17- 5-25 cm for females; weight 1-9- 3-95 kg for males and 1-8- 3-7 kg for females. A small, stout fox with an elongated body and short legs. Muzzle short and thin, extending into a rather rounded forehead. The agouti hair on the torso contributes to its dark appearance. Rufous markings on the ears and along the legs below the knees and elbows. White markings under the chin, along the lower mandible, on the underbelly and on the upper and inner part of the legs. The tail is dark gray, relatively short and quite bushy—all useful traits for distinguishing this species from congenerics. The skull is shorter and the auditory bulla smaller than the South American Gray Fox, but the dentition is heavier. Dental formulais 13/3, C 1/1, PM 4/4, M2/3=42.

Habitat. Generally believed to be a forest obligate species found only in southern temperate rainforests. They inhabit dense Valdivian forest, which is very moist all year round. The forest is dominated by fruit-bearing trees in the family Mirtaceae ; there are a few native conifers and several species of broad-leaved evergreens. Radio-tracking along a gradient of disturbance on Chiloé indicated that, in decreasing order, foxes use old-growth Valdivian forest followed by secondary forest followed by pastures and openings; about 70% of home ranges comprised old-growth forest. However, when compared to the availability of each forest gradient, foxes showed preference for secondary forest and avoided old growth. On the Pacific coast of Chiloé, Darwin’s Foxes live in a fragmented environment of coastal sand dunes and dense evergreen forest. On the northern part of the island, they use a relatively flat, fragmented landscape of broadleaf forest and cow pasture. The mainland population uses dense forest; animals are found with decreasing frequency in dense monkey-puzzle tree-southern beech (Araucaria-Nothofagus spp.) forest, open Nothofagus forest and open pasture, respectively.

Food and Feeding. Omnivorous, with a broad diet, and highly opportunistic. These traits facilitate its survival in a highly fluctuating environment with low prey availability. Fecal analysis showed that the mainland population ate primarily small mammals, followed, in decreasing levels of importance, by reptiles, insects, birds, and arachnids. The proportions of these prey classes fluctuated strongly according to season. Berries were also included in the diet, occurring in about. 20% of the feces. On the mainland Darwin’s Foxes rely heavily on the seeds of monkey-puzzle trees from March to May. On Chiloé,fecal analysis revealed that insects were the most abundant food item in the diet during the warm season, followed by amphibians, mammals, birds, and reptiles; 49% offeces contained seeds. During late summer and fall, the diet was almost entirely fruits of Mirtaceae trees. Foxes may be considered a key species because of their role in dispersing the seeds of forest plants. An experiment indicated that a high percent age of the seeds of one tree species ( Amomyrtus luma ) collected from feces germinated underfield conditions. Darwin’s Foxes also eat carrion in small amounts, as evidenced by the remains (e.g. hair) of sheep, pigs, cattle, and horses in feces. Local settlers reported that lone foxes also kill Southern Pudu deer (Pudu puda; about 10 kg in weight) by biting their ankles and then the throat. In addition, coastal foxes feed on shellfish and shorebirds, and have been observed feeding on large brown algae on the beach.

Activity patterns. Darwin’s Foxes seem to concentrate their activity during the daytime in forested areas. In Nahuelbuta, they forage mainly at night, when the sympatric and larger South American Gray Fox is less active. They have also been observed hunting ducks at midday in a coastal marsh.

Movements, Home range and Social organization. In Chiloé¢, radio-tracking indicated that Darwin’s Foxes are solitary when not breeding, but will congregate at food sources, such as carcasses and seaweed stranded on beaches. A pair appears to be the basic social unit during the breeding season. Home ranges average about 1-6 km * for males and 1-5 km? for females. Given the very large range overlaps among neighboring foxes, and that individuals share their home range with an average of 4- 7 males and 3- 3 females, Darwin’s Fox appears to be non-territorial. On the mainland, pairs persist throughout the year, and are often found in close proximity. In contrast with the Chiloé population, mainland pairs have been known to share their home ranges with offspring from previous years. All family members associate closely with each other, showing very little aggressive behavior towards one another. To date, no evidence has been reported of oldersiblings serving as helpers to new litters. The maintenance of a large family group may be influenced by a paucity of suitable territories for potentially dispersing juveniles. Dispersal appears to be delayed and may be opportunistic.

Breeding. On the mainland, lactating females have been caught in October and pups have been documented leaving the den area and venturing out with both parents in December. Litter size is estimated to be 2-3 pups. Weaning occurs in February. During this period the female spends relatively less time with the pups, and a greater proportion of their interactions are agonistic, whereas the male spends more time playing with and grooming the pups. A den was located in a rock cavity (2 m deep) in Araucaria—Nothofagus forest with a bamboo understory, and a small pup was found denning in a hollow rotten log. During mating, males and females are together for a few days. During the first few weeks after parturition, females move little and apparently stay in the den.

Status and Conservation. CITES Appendix II. Classified as Critically Endangered on The IUCN Red List. Population size is currently estimated as less than 250 mature individuals with most of the foxes occurring in Chiloé Island. Protected by Chilean law since 1929, but enforcement is not always possible and some poaching occurs. The conservation status is “rare” on the mainland and “vulnerable” on Chiloé Island. More recently, Darwin’s Fox has been considered as “critical”, becoming the second most urgent Chilean terrestrial mammal conservation priority. The mainland population is reported to be vulnerable and its survival uncertain if current environmental trends continue. Although the species is protected in Nahuelbuta National Park, foxes are exposed to substantial mortality risks when they move to lower, unprotected private areas in search of milder conditions during the winter. Some foxes even breed in these areas. Unleashed dogs are common both on Chiloé and in Nahuelbuta and represent a significant conservation threat. Dogs have been reported to attack and kill foxes and are also vectors of potentially fatal diseases. The island population, being protected in Chiloé National Park, appears to be relatively safe. This 430 km ® protected area encompasses most of the pristine rainforest on the island. However, although the park appears to have a sizable fox population, foxes also live in the surrounding areas where substantial forest cover remains. These areas are vulnerable and continuously subjected to logging, forest fragmentation, and poaching by locals.

Bibliography. Armesto et al. (1987), Cabrera (1958), Cofré & Marquet (1999), Glade (1993), Iriarte & Jaksic (1986), IUCN (2008), Jaksic et al. (1990), Jiménez (2000), Jiménez & McMahon (2004), Jiménez et al. (1990), Mc-Mahon (2002), McMahon et al. (1999), Medel et al. (1990), Miller et al. (1983), Osgood (1943), Pine et al. (1979), Redford & Eisenberg (1992), Spotorno (1995), Yahnke (1995), Yahnke et al. (1996).

Figures

On following pages: 16. South American Gray Fox (Pseudalopex griseus); 17. Pampas Fox (Pseudalopex gymnocercus); 18. Sechuran Fox (Pseudalopex sechurae); 19. Hoary Fox (Pseudalopex vetulus); 20. Northern Gray Fox (Urocyon cinereoargenteus); 21. Island Fox (Urocyon littoralis).

Distribution. Endemic to Chile , with a disjunct distribution in the forests of Chiloé Island, and on the mainland coastal mountains in Nahuelbuta National Park. Evidence of a new population was foud recently at Punta Chan Chan, N of Valdivia.