Large-scale assessment of the presence of Darwin’s fox across its newly discovered range
Introduction
The Darwin’s fox (Lycalopex fulvipes) is an Endangered canid, endemic to Chile (Silva-Rodríguez et al., 2016). Up to recently this fox was known to occur in just two areas: a single site in mainland Chile (Nahuelbuta mountain range) and an island (Chiloé) located a few kilometers away from mainland, but nearly 500 km south of Nahuelbuta (Jiménez and McMahon, 2004). The lack of Darwin’s fox records in the coastal areas between Nahuelbuta and Chiloé Island was intriguing, because there were still areas of native forest where undiscovered populations could persist (Vilà et al., 2004). To address this gap, Vilà et al. (2004) surveyed several sites along the Coastal Range between Nahuelbuta and Chiloé Island. Their efforts led to the finding of a pelt in Punta Chanchán (39°21′ S, 73°14′ W). In addition, local people reported foxes that matched Darwin’s fox in Chaihuín (40°1′ S, 73°25′ W) and Punta Chanchán (Vilà et al., 2004). Unfortunately, these surveys did not provide evidence of living foxes. This situation changed with the recent finding of a fox killed by a dog (Canis familiaris) in Lastarria, Gorbea (39°11′ S, 72°46′ W; D’Elía et al., 2013) and camera trap records in three protected areas in the Valdivian Coastal Range (Farias et al., 2014). These findings provided strong evidence that the area occupied by Darwin’s foxes in mainland was much larger than previously thought (D’Elía et al., 2013; Farias et al., 2014; Silva-Rodríguez et al., 2016).
In addition to the new distributional insights, in the last decade there have been important advances in the understanding of the ecology of the Darwin’s fox. Recent research on habitat use in the Nahuelbuta mountain range has shown that Darwin’s fox is positively associated to native forest and negatively associated to the occurrence of domestic dogs (Moreira-Arce et al., 2015), and understory appears to play an important role in the presence of this species (Moreira-Arce et al., 2016). In Chiloé Island, this canid uses a wider diversity of land cover types and associated food resources (e.g., fruits, terrestrial and intertidal invertebrates, vertebrates; Jiménez, 2007), but in fragmented areas of the island it is associated to large forest fragments (Farias and Jaksic, 2011). Home range size varies between 103 and 488 ha, and core areas (50% fixed Kernel) range between 30 and 130 ha (based on seven foxes, Jiménez, 2007). Threats such as diseases are little understood (e.g., Cabello et al., 2013). However, seroprevalence to pathogens such as canine distemper virus is high in domestic dogs (Sepúlveda et al., 2014; Acosta-Jamett et al., 2015) and invasive American minks (Neovison vison) (Sepúlveda et al., 2014), suggesting an important risk for the species (Silva-Rodríguez et al., 2016). Several studies—that did not target the species—provide important information that is relevant to understand the drivers of the threats affecting Darwin’s fox. For example, there is ample information on land cover change (e.g., Echeverría et al., 2012; Miranda et al., 2015; Zamorano-Elgueta et al., 2015; Otavo and Echeverría, 2017) and domestic dogs (e.g., diet, habitat use, interactions with wild animals, exposure to pathogens, etc.; see Silva-Rodríguez et al., 2010; Silva-Rodríguez and Sieving, 2012; Sepúlveda et al., 2014, 2015; Acosta-Jamett et al., 2015). The information available suggests that domestic dogs and associated pathogens as well as forest loss are the main threats for the conservation of the Darwin’s fox (Silva-Rodríguez et al., 2016).
In the Valdivian Coastal Range, other than the fact that they are present (Farias et al., 2014), little is known about the ecology of the Darwin’s fox and how it compares to other populations. Using data from survey efforts conducted along the Coastal Range and Chiloé Island, as well as the results of monitoring efforts in two protected areas, we aimed to address three specific objectives. First, we aimed at determining if the detection rates—the quotient of detection events and sampling effort (see Carbone et al., 2001; Rovero and Marshall, 2009)—of Darwin’s foxes differed between the mainland and the insular population. Furthermore, given that we expected foxes to be negatively associated to human disturbance—as reported for the northern population in Nahuelbuta (Moreira-Arce et al., 2015)—we asked whether differences in fox detection rates between mainland and the island held at different levels of human disturbance. For this purpose, we used two proxies of human disturbance: forest cover and domestic dogs. Second, we aimed to quantify the proportion of sites occupied by Darwin’s foxes where domestic dogs are also present (i.e., the scope of a threat; see Foundations of Success, 2009). The scope of the dog threat was considered high for the IUCN Red List (Silva-Rodríguez et al., 2016), but has not been formally quantified. Finally, our third objective was to quantify the area used by Darwin’s foxes in two neighboring protected areas, thus providing an early baseline for the newly discovered population of this endangered species.
Section snippets
Study sites
Our study area extends for over 400 km from Los Ríos region to the southern end of Chiloé Island (Fig. 1). Most of the surveyed sites are located in the Coastal Range of Los Ríos and Los Lagos administrative regions. The area is characterized by high precipitations, and is dominated by Valdivian evergreen forests (mainland) and Chiloé evergreen forests (Smith-Ramírez, 2004).
In addition to the surveys, we conducted intensive work in two neighboring protected areas located in the Valdivian
Darwin’s fox surveys along the coastal range
Darwin's fox was recorded at 14 out of 30 sites (Fig. 1), including 42.1% of the sites surveyed in mainland and 54.5% in Chiloé Island. Records were distributed throughout Chiloé Island, but were less common at the most intervened and densely populated northeastern portion of the island (Fig. 1). On the other hand, Darwin's fox records in mainland were mostly concentrated in the northern portion of the sampled Coastal Range and a single locality at the southern extreme (Fig. 1). Domestic dogs
Discussion
Our results support our previous findings concerning the presence of the Darwin’s fox in the Valdivian Coastal Range (Farias et al., 2014) and provide evidence of its presence approximately 160 km to the south of the previously described mainland locations (site 19, Fig. 1). The information on this new record was previously used to assess the Darwin’s fox conservation status (see Silva-Rodríguez et al., 2016). We did not obtain Darwin’s fox records in six locations between the Bueno River and
Acknowledgements
This article is dedicated to the memory of our friend and colleague Don Omar Ponce, a great park ranger, and a better person.
Work in the Valdivian Coastal Reserve and Alerce Costero National Park is part of the Monitoring Programs of both protected areas. The use of the monitoring datasets was authorized by The Nature Conservancy and CONAF, respectively. Monitoring in the Valdivian Coastal Reserve was funded by Parc Zoologique de Paris, Museum National d'Histoire Naturelle; The Nature
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Equal contributors.