Darwin's fox

Darwin's fox[1]
CITES Appendix II [3]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Genus: Lycalopex
Species:
L. fulvipes
Binomial name
Lycalopex fulvipes
(Martin, 1837)
Darwin's fox range
Synonyms
  • L. lagopus (Molina, 1782)

Darwin's fox or Darwin's zorro (Lycalopex fulvipes) is an endangered canid from the genus Lycalopex. It is also known as the zorro chilote or zorro de Darwin[2] in Spanish and is endemic to Chile, where it lives in the temperate rainforests of Nahuelbuta National Park, the Cordillera de Oncol, Cordillera Pelada, and Chiloé Island.[4] This small, dark canine weighs 1.8 to 3.95 kg (4.0 to 8.7 lb), has a head-and-body length of 48 to 59 cm (19 to 23 in) and a tail that is 17.5 to 25.5 cm (7 to 10 in).[5] Darwin's fox displays no key differences between male and female other than the fact that the male has a broader muzzle.[6] Males display no territorial behavior and are not aggressive towards other males roaming around their territory.[6]

Darwin's fox is adapted to life in southern temperate rainforests, with characteristics that differentiate it from other Lycalopex species. Darwin's fox has shorter legs, a darker coat, and broader head than its closest relative South American gray fox (L. griseus).[7] Its pelage has a mottled coat with black and gray fur tinged by reddish tones on its ears and lower legs.[8] White markings are found under the chin, along the lower mandible, on the underbelly, and inner portions of the legs.[8] The short, busy, dark gray tail is a diagnostic characteristic used to distinguish from other related species.[9]

Darwin's fox was first collected from San Pedro Island off the coast of Chile by the naturalist Charles Darwin in 1834, after whom the species is named.[10] It was long held that Darwin's fox was a subspecies of L. griseus; however, the discovery of a small population of Darwin's fox on the mainland in Nahuelbuta National Park, in 1990.[9] and subsequent genetic analysis has clarified the fox's status as a unique species.[11]

The species is thought to number under 1,000 mature individuals, with most found on Chiloé Island and smaller populations on the mainland.[12] Once considered critically endangered, it was reclassified as endangered in 2016.[2] Its main threats come from domestic and feral dogs, which spread diseases and attacks foxes, along with ongoing habitat loss from agriculture and forestry.[7] Conservation efforts focus on managing disease risk through dog vaccination near protected areas.[2]

Taxonomy and evolution

Lycalopex is a South American genus of canine, which is distantly related to wolves and is technically not a fox. When Charles Darwin collected a specimen from San Pedro Island in Chiloé Archipelago in December, 1834, during the Beagle survey expedition, he observed that this "fox (of Chiloe, a rare animal) sat on the point & was so absorbed in watching [survey work], that he allowed me to walk behind him & actually kill him with my geological hammer."[13] In the 1839, publication of his Journal and Remarks, Darwin said "This fox, more curious or more scientific, but less wise, than the generality of his brethren, is now mounted in the museum of the Zoological Society." He said it was "an undescribed species,"[14] indicating that it was distinct from the species (L. culpaeus and L. griseus) that occur on the mainland. Later, Darwin's fox was classified as a subspecies (Lycalopex griseus fulvipes) of the latter.

Darwin's fox does not interbreed with the other Lycalopex species, only lives in forests, and is smaller and darker-colored than the other species. In 1990, a small population of Darwin's fox was found on the mainland in the forested Nahuelbuta National Park, indicating that the fox was not endemic to the island. Analysis of mitochondrial DNA of Darwin's fox and the gray fox showed two patterns, indicating Darwin's fox was a new species, closely related to the Sechuran fox.[11] The present restricted range is a relic of a much wider former range. Zoologists noted the distinctiveness in the ecological niche, appearance, and behavior of this species.[11] Darwin's fox is differentiated from the gray fox in being darker; having shorter legs; a broader, shorter skull; smaller auditory bullae; a more robust dentition; and a different jaw shape and style of premolar occlusion.

In the late Pleistocene, Chiloé Island was connected to mainland Chile by a land bridge. The land bridge was severed about 15,000 years ago when the sea level rose following the last glaciation.[15] This created two isolated populations of Darwin's fox.[16]

Diet

Darwin's fox is an opportunistic omnivore and has a varied diet. In general, most of its diet is believed to come from insects, however, small mammals, birds, reptiles, fruits and seeds also make up its diet.[17]

Scat analysis of Darwin's fox populations in Nahuelbuta National Park consisted mostly of mammals, including Akodon, Monito del monte, Southern big-eared mouse, and long-clawed mole mouse, although it also contained birds, reptiles, insects, arachnids, and plants.[18] Scat analysis of populations on Chiloé Island consisted mostly of invertebrates, especially arthropods and Cratomelus armatus, rodents, and fruits, but also contained fish, reptiles, birds, and Monito del monte.[19] Intake of specific dietary items varies seasonably in this population, with a greater intake of rodents and lesser intake of invertebrates in winter.[19]

Ecology

Darwin's fox inhabits temperate rainforest ecosystems of southern Chile.[20] Field studies in Nahuelbuta have documented individuals occurring in areas characterized by dense native forest vegetation.[21] Radio-telemetry research further indicates use of Araucaria–Nothofagus forest, evergreen forest, and, less frequently, open pasture habitats.[5] In the Valdivian Coastal Range, the species has been recorded in old-growth and secondary evergreen forests as well as unmanaged eucalyptus plantations.[20] Occupancy of Darwin's fox increases in areas with greater native forest cover and declines where road density is higher.[2]

They only occur in areas of primary forest on Chiloé and on the mainland, where habitat use includes second-growth forest and shrubland, with occasional use of coastal dune systems.[6] Home ranges vary between approximately 103 and 488 hectares, with substantial overlap among individuals.[6] In 2012 and 2013, the presence of the Darwin's fox at Oncol Park, Alerce Costero National Park and the Valdivian Coastal Reserve was confirmed through camera trapping.[20]

They are most active at twilight and before sunrise.[5] Status surveys reported that past populations on Chiloé Island had a stable size of 250 individuals in protected areas and a decreasing population of 250 individuals in other areas of Chile.[5] While the mainland contained about 78 individuals in protected areas and a decreasing population of 10 individuals in other areas.[5] In a 2012 annual report by The Mohamed bin Zayed Species Conservation Fund, the total population is less than 250 mature individuals with at least 90% of the population occurring in one subpopulation on Chiloé Island.[22] Results also showed that Darwin's fox populations exist both inside the Nahuelbuta National Park and in the surrounding region up to 30 km north and northwest of its borders.[22]

A 2016 IUCN assessment estimated a minimum of 412 mature individuals on Chiloé Island and 227 mature individuals in mainland areas, for a total of approximately 639 mature individuals.[2]

Although the species is protected in Nahuelbuta National Park, substantial mortality sources exist when foxes move to lower, unprotected private areas in search of milder conditions during the winter.[5] The population was considered as critically endangered because its main population occurred in one island and their habitat was declining due to human impact.[23]

Conservation status

The species was previously classified as Critically Endangered by the IUCN, but in 2016 was downlisted to Endangered, as its area occurrences is apparently substantially larger than originally believed. Current estimates of the total population are still low, with an estimated minimum 227 individuals on the mainland and 412 on Chiloé Island. Fragmentation of forest adjacent to the national park and on the island is a concern for their conservation, and feral dogs may pose the greatest threat to their survival by spreading disease or directly attacking. Persecution by people who think that the foxes attack domestic fowls, though they pose little threat, is also a potential problem.[2] Since rural dogs are believed to spread diseases to the Darwin's fox, such as canine distemper and rabies, free vaccines are provided for domestic dogs by a group of scientists in Chile in an effort to prevent spillover between populations.[24]

The only known captive population is maintained by Fauna Adina near Villarrica, Chile, where the species has successfully reproduced.[25]

In September 2023, the "Plan for the Recovery, Conservation and Management of Darwin's fox" highlights the importance of address major knowledge gaps regarding Darwin's fox. The plan was submitted to the Chilean Ministry of Environment.[12] In 2025, the Darwin's fox was added to the Government of Chile's RECOGE plan, allowing greater protections for the species and its habitats.[26]

Future conservation efforts for Darwin's fox could integrate genomic technologies with traditional conservation strategies. High-throughput sequencing (HTS) can address the knowledge gap on species' genetic diversity and pathogen exposure. The molecular data can be essential for developing effective management plans. However, in South America, the application of HTS in conservation research is still limited, mainly because of funding shortages. The availability of advanced genomic equipment and analytical expertise is limited as well.[12]

Diseases

The species is often plagued by Mycoplasma haemocanis. The already endangered fox is prone to this infection because the infection's bacteria attach themselves to surface red blood cells of many mammals, and although the species is believed to be no major threat to human life it can spread to humans, dogs, cats, and other wildlife species. The bacteria also seem to spike when located close to any major habitat inhabited by humans as well as where there is a large population of wild dogs present near the species. Researchers are testing RNA subunits of RNase P gene and out of 10 foxes, nine were infected. Even though they are considered "sick", they have no external symptoms (Cabello, 2013). Studies show that many foxes risk of catching the deadly bacteria inclines as they age leaving many older foxes vulnerable. Although the disease is prevalent in this species, little to nothing is known about this disease.[27]

Disease spread from rural, domestic dogs is considered a threat in Darwin's fox populations.[28] Rural dogs often roam free in Chile and are not provided with any veterinary care. Interactions with these dogs is thought to lead to pathogen transmission.[29] A 2022 study determined dietary overlap in rural dogs and Darwin's foxes despite differences in habitat use by analyzing carbon and nitrogen isotopes in hair samples, concluding shared food resources in human-modified landscapes can be detrimental to the Darwin's fox due to pathogen spillover.[30] Canine distemper and rabies are believed to be able to spread to Darwin's foxes from rural dogs, however, there is little evidence of either disease being present in Darwin's fox populations.[31][12]

Darwin's foxes are plagued by the Mycoplasma bacteria although it does not cause obvious symptoms. While it is known that the Mycoplasma haemocanis can transmit through brown dog ticks and attach themselves to the surface of red blood cells of many mammals, including humans, dogs, and cats, the specific mode of transmission in the Darwin's fox is unknown as Chiloé island is not known to harbour any canine ticks. Despite this, screening for the Mycoplasma characteristic 16S rRNA gene showed M. haemocanis prevalence is higher in Darwin's foxes than rural dogs and risk of contracting M. haemocanis inclines with age.[29] In 2013, Mycoplasma haemofelis was detected in Darwin's fox populations, marking the first time a feline hemoplasmic pathogen had be detected in a canid. There is no clear geographical relationship for Mycoplasma prevalence in Darwin's fox populations and it is largely unknown how it affects the species.[32]

There is also evidence of Toxoplasma gondii and Leptospira in Darwin's fox populations which may pose threat to the species. Specifically, T. gondii was widespread in Darwin's fox populations that were living in non-anthropized areas. T. gondii exposure in Darwin's fox has no correlation with specific risk factors such as sex, age, season, or degree of anthropization. Darwin's foxes were reported to have one of the highest prevalence of T. gondii antibodies in Chilean wildlife and foxes worldwide, potentially a sign of frequent infections.[28]

Due to the lack of intraspecies interaction, Darwin's fox has limited pathogen spillover from members of its own species but also limited acquired immunity.[32] Because of this, some researchers believe they may be particularly vulnerable to epidemics. For instance, Canine distemper virus (CDV) is considered as a potential threat to Darwin's foxes. Among the samples collected from Darwin's fox, no sign of exposure to CDV was found. Due to the lack of immune exposure to this virus, a spillover of CDV from domestic dogs could result in significant population mortality.[31]

References

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  10. ^ Medel, Rodrigo G.; Jiménez, Jaime E.; Jaksić, Fabian M.; Yáñez, JoséL.; Armesto, Juan J. (1990). "Discovery of a continental population of the rare Darwin's fox, Dusicyon fulvipes (Martin, 1837) in Chile". Biological Conservation. 51 (1): 71–77. Bibcode:1990BCons..51...71M. doi:10.1016/0006-3207(90)90033-L.
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  28. ^ a b Hidalgo-Hermoso, Ezequiel; Cabello, Javier; Verasay, Juan; Moreira-Arce, Dario; Hidalgo, Marcos; Abalos, Pedro; Borie, Consuelo; Galarce, Nicolas; Napolitano, Constanza; Sacristán, Irene; Cevidanes, Aitor; Ramírez-Toloza, Galia; Farias, Ariel; Cataldo, Sophia Di; Lagos, Rocio (2022-01-04). "Serosurvey for Selected Parasitic and Bacterial Pathogens in Darwin's Fox (Lycalopex Fulvipes): Not Only Dog Diseases Are a Threat". Journal of Wildlife Diseases. 58 (1): 76–85. doi:10.7589/JWD-D-21-00024. ISSN 0090-3558. PMID 34714909.
  29. ^ a b Di Cataldo, Sophia; Hidalgo-Hermoso, Ezequiel; Sacristán, Irene; Cevidanes, Aitor; Napolitano, Constanza; Hernández, Claudia V.; Esperón, Fernando; Moreira-Arce, Darío; Cabello, Javier; Müller, Ananda; Millán, Javier (2020-06-02). Dudley, Edward G. (ed.). "Hemoplasmas Are Endemic and Cause Asymptomatic Infection in the Endangered Darwin's Fox (Lycalopex fulvipes)". Applied and Environmental Microbiology. 86 (12) e00779-20. Bibcode:2020ApEnM..86E.779D. doi:10.1128/AEM.00779-20. ISSN 0099-2240. PMC 7267207. PMID 32276983.
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  • Media related to Pseudalopex fulvipes at Wikimedia Commons
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