Date Published: February 28, 2018
Publisher: Public Library of Science
Author(s): Galo Zapata-Ríos, Lyn C. Branch, Bi-Song Yue.
Although the Andes have long been occupied by people, habitat loss, fragmentation through deforestation, and other human activities such as introduction of invasive species have increased drastically during the past century. The Ecuadorian Andes are considered a biodiversity hotspot. However, the fauna and threats to the region are poorly studied, and understanding of factors that shape the distribution of species in habitats disturbed by human activities is needed to identify and mitigate region-wide threats to wildlife. We evaluated factors associated with patterns of occurrence of Andean carnivores in landscapes of the northern Ecuadorian Andes, particularly habitat loss, fragmentation, and occupancy of domestic dogs, and determined whether thresholds occurred for these factors beyond which carnivore occurrence declined markedly. Five study areas (each 20 x 20 km) were surveyed with a total effort of 2,800 camera trap nights. Occupancies of four of the eight carnivores known from the region were best predicted by occupancy of domestic dogs rather than measures of habitat loss and fragmentation [Andean fox (Pseudalopex culpaeus), puma (Puma concolor), striped hog-nosed skunk (Conepatus semistriatus), and Andean bear (Tremarctos ornatus)]. The two largest carnivores, puma and Andean bear, demonstrated significant threshold responses to the presence of domestic dogs at two sites. Four smaller carnivores were recorded too infrequently to model occupancy, and at least two of these species appear to be in decline. The magnitude of domestic dog impacts on native species in tropical areas like the Ecuadorian Andes currently are not recognized. Results of our study indicate that small and large carnivores are in urgent need of conservation and clearly point to dogs as a significant threat to a broad range of native species.
Mammalian carnivores are thought to be particularly vulnerable to local extinction in disturbed landscapes because of their large home ranges, low population sizes, and direct persecution by humans [1,2]. Habitat loss and fragmentation often lead to decreased population size, increased isolation, and edge effects that increase extinction risk [3–5]. Landscape change also often is accompanied by other human disturbances such as hunting and introduction of domestic animals and other invasive species that affect carnivores [6,7]. For example, retaliation killing of carnivores that prey on livestock is common in human-dominated landscapes across the globe [8,9]. Substantial evidence also indicates that domestic dogs (Canis lupus familiaris) are a significant threat to wildlife [10,11]. Domestic dogs are the most abundant carnivore on Earth and have the potential to have large impacts on native carnivores because they can function as predators and competitors, as well as spread diseases [10,11,12–16]. Despite the long history of research on carnivores, particularly in temperate regions, the ecology of the vast majority of carnivore species and their responses to human-caused disturbances are poorly known, resulting in a significant gap for design of strategies to mitigate threats to these species.
Domestic dogs were common in all five study areas. The Andean fox and striped hog-nosed skunk, which occur in a broad array of native and disturbed habitats, were the most commonly detected native carnivores (S2 Table) and the only species recorded frequently in all study areas. The Andean bear and puma were recorded in three and four study areas, respectively, but we only had enough data to construct models for Filo Curiquingue and San Marcos. The long-tailed weasel and mountain coati were detected only occasionally in two study areas (Filo Curiquingue and San Marcos), and the pampas cat and Colombian weasel were not detected. These four species were not included in analyses.
Current occupancy of four native Andean carnivores, including three habitat generalists (puma, Andean fox, and striped hog-nosed skunk) and one specialist (Andean bear), was best predicted by the presence of domestic dogs rather than habitat loss and fragmentation. These models provide significant evidence that both free-ranging and feral dogs negatively influence occupancy of Andean carnivores. Dogs affect populations of native wildlife by direct predation, through exploitative competition (asymmetric competitive abilities in obtaining limited resources), interference competition (interactions such as spatial exclusion, harassment, and intraguild predation), and by acting as vectors of disease such as canine distemper, parvovirus, and rabies [10,12,13,15,16]. Free-ranging domestic dogs usually occur in close proximity to human-dominated areas, rely heavily on human sources of food for subsistence, and do not respond numerically to potential declines of native prey [39,62,63]. Thus, free-ranging domestic dogs represent a substantial threat to Andean carnivores and other native species because they have the potential to maintain predation pressure and competition levels as native prey and native carnivores decline. Models for our most central study sites (Filo Curiquingue and Fuya-Fuya) provide support for this scenario, as occupancy of domestic dogs declined as distance from roads and houses increased, and occupancy of native carnivores was negatively related to the presence of dogs. In contrast, at remaining sites in the north and south of our study region, the negative relationship between occupancy of dogs and native carnivores was maintained but occupancy of domestic dogs increased with distances from houses and roads, likely reflecting the presence of feral dogs in these study sites. Local people report observations of feral dogs in these areas. Also, camera trapping studies in Cayambe-Coca National Park (Fig 1) in undisturbed habitats with and without feral dogs documented reduced abundance of medium and large mammals and changes in their activity patterns where feral dogs were present . The results we report here suggest that the impacts of feral dogs on wildlife are widespread in the Ecuadorian highlands and, similarly, that free-ranging dogs are a significant threat.