Domestic dogs and associated diseases are likely the main threats for Darwin’s Foxes (Jiménez and McMahon 2004). Dogs are a common problem in Chilean protected areas, including each of those where the Darwin’s Fox is present. Domestic dogs would represent a risk for foxes through intra-guild killing, as well as through disease transmission (Jiménez and McMahon 2004, Cabello et al. 2013a,b). The death of Darwin’s Foxes due to dog attacks has been reported both on the mainland (D’Elia et al. 2013) and in Chiloé (Espinosa 2011, J. Jiménez pers. obs.). Moreira-Arce et al. (2015a) found a negative correlation between the areas used by dogs and foxes in Nahuelbuta. Accordingly, in Chiloé Island, Darwin’s Foxes are rare or absent from old-growth forests frequently visited by dogs, while they are frequently recorded at camera traps in scrublands when dogs are absent (A. Farías pers. obs.), suggesting spatial displacement. It is important to note that the dog problem that affects Darwin’s Foxes, is caused in most, if not all, cases by poorly managed free-ranging dogs and not feral dogs (D. Moreira pers. obs., E.A. Silva-Rodríguez et al. pers. obs.).
The risk of disease spillover from dogs (mainly Canine Distemper Virus, CDV) is considered a major threat for Darwin’s Fox populations (e.g., Jiménez and McMahon 2004, Silva-Rodríguez et al. 2015). Exposure of dogs to CDV has been shown in the proximity of Nahuelbuta National Park (Acosta-Jamett et al. 2015b) and Valdivian Coastal Reserve-Alerce Costero National Park (Sepúlveda et al. 2014). Furthermore, exposure to CDV has been reported for invasive American minks (Neovison vison) in areas were the Darwin’s Fox is present (Sepúlveda et al. 2014), as well as for Chilla (Lycalopex griseus) and Culpeo (Lycalopex culpaeus) in other regions (Acosta-Jamett et al. 2015a). Additionally, Jiménez et al. (2012) reported the death of three radio-collared foxes in Chiloé in sympatry with free-ranging dogs, suggesting that mortality could have been caused by CDV, although conclusive evidence was not available. CDV epizootics in canids have been reported worldwide (e.g., Goller et al. 2010, Di Sabatino et al. 2014), and CDV was implicated in a major decline in the population of the Island Fox (Urocyon littoralis) in Santa Catalina Island (Timm et al. 2009). In South America, Megid et al. (2009, 2010) reported CDV-related mortalities in wild canids in Brazil, and in Chile, Moreira and Stutzin (2005) reported the death of 27 Chilla and Culpeo foxes due to CDV in Coquimbo Region. The lack of conclusive evidence of declines due to CDV in the Darwin’s Fox may be well explained by lack of information, rather than by the absence of outbreaks.
Darwin’s Foxes can also be subject to human-caused mortality. According to J. Jiménez (pers. obs.) and Espinosa (2011), local people in Chiloé reported killing foxes because they attack domestic animals and to obtain their fur. Foxes rescued from traps as well as captured and translocated after predation on poultry have also been reported in Chiloé (J. Cabello pers. obs.). Stowhas (2012) also indicated that local people reported killing foxes (undetermined species) in an area that included the surroundings of Oncol Park, Alerce Costero National Park, and Valdivian Coastal Reserve, as a response to predation on poultry. In Nahuelbuta range, foxes (without distinguishing to the level of species) are often considered as problem animals (Sánchez et al. 2014). However, Darwin’s Fox is not commonly persecuted or killed by local people (but see McMahon et al. 1999) and its conservation would show a high social support (D. Moreira pers. obs.).
Forest loss is an important threat. The highest rates of forest loss occur in the coastal range of the Araucanía Region, where Nahuelbuta is located. There, the annual loss rate observed for the 1999-2008 period reached 4.8%, the second highest reported for Chilean temperate forest (Miranda et al. 2015). For the Valdivian Coastal Range, the net forest loss between 1985 and 2011 was 5.1% (and the gross loss reached 30%), but the loss rate was higher for the 1985-1999 period than for the 1999-2011 period (Zamorano-Elgueta et al. 2015). In northern Chiloé and Maullín, the annual rates of forest loss was close to 1% (1985-2007), although in the case of Chiloé this rate rose to 1.4% for the 1999-2007 period (Echeverría et al. 2012). Both in the Araucanía and Valdivian cases, cleared native forest was frequently converted to forestry plantations (Miranda et al. 2015, Zamorano-Elgueta et al. 2015). Although Darwin’s Fox has been recorded in plantations (Farías et al. 2014, J. Jiménez pers. obs.), evidence from the population in Nahuelbuta shows that foxes select for native forest (Moreira-Arce et al. 2015a). However, if managed through an increase of native understory cover, commercial plantations may provide complementary habitats and food resources for this species (Moreira-Arce et al. 2015b). Human-induced fires are an always-latent threat, especially for the Nahuelbuta range (D. Moreira pers. obs.). On the other hand, deforestation may favour other (larger sized) fox species (i.e. Lycalopex griseus and L. culpaeus), better adapted to open areas (e.g., Silva-Rodríguez et al. 2010), which can displace Darwin’s Foxes (Jiménez et al. 1991). The indirect effects of changes in land cover through alteration of interaction webs are still insufficiently known.
Indirect threats that need to be considered include the construction of bridges, highways and roads. Of major concern is the projected construction of the bridge connecting Chiloé to the mainland. This bridge, if barriers are not implemented, may facilitate the invasion of the island by other species such as congeneric foxes and Pumas (Puma concolor), with unknown, but potentially serious consequences for these populations. Road construction and improvement is an additional concern, given that they facilitate dog (Moreira-Arce et al. 2015a, Sepúlveda et al. 2015) and human movement, and can lead to land cover change (Wilson et al. 2005). Existing roads, as well as the construction of new roads and/or the improvement of existing public roads, is a concern for Nahuelbuta (Sánchez et al. 2014), the Valdivian Coastal Range (Silva-Rodríguez et al. 2015) and for Chiloé (J. Cabello pers. obs.).
Other threats that need to be taken into account include the translocation of rescued and problem animals (J. Cabello pers. obs.) and illegal tenure of foxes as pets (J. Jiménez pers. obs.).