Differential effects of habitat on the occupancy of jaguars, pumas and sympatric carnivores in Sonora, Mexico
Borrego, Charles Steven
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Declines in wild cat populations across the world have led to international efforts to conserve the remaining, declining populations of some species. The Sierra Madre Occidental in Sonora, Mexico is a remote region containing a diverse guild of carnivores: jaguars, pumas, bobcats, ocelots, coyotes and gray foxes. Jaguars are not only rare, cryptic and wide ranging, but also an endangered species that is emblematic of an umbrella species for conservation. To study the effect of habitat type, elevation and roads of jaguars and sympatric carnivores, I set 288 remote cameras (14-49 days) across 250 square km during August-December in 2008-2009 across a consortium of 11 ranches in northeastern Sonora. I placed cameras along roads, trails and arroyos to generate binary photographic "detection" encounter histories. I used species-specific detections in conjunction with likelihood-theory based occupancy modeling to estimate species specific detection probabilities and occupancy rates across the carnivore guild. Seven jaguars (4 F, 3 M) were detected on 33 occasions at 21 stations (jaguar detection = 0.11, (SE= 0.04)). Elevation of jaguar detections ranged from 633-1273 m, corresponding with thorn scrub vegetation. Small sample size resulted in the null constant occupancy model as the best model, however the competing model distance to active roads provided predicted jaguar habitat occupancy was lower directly on active roads (psi= 0.04, (SE= 0.04)) and substantially greater (psi=0.92 (SE= 0.32)) when ?7.4 km from an active road. Pumas were more ubiquitous, with 162 detections at 112 stations, and habitat occupancy ranging from 0.11-0.20 psi across various habitat conditions. Ocelot occupancy was highest at stations lacking recorded human activity (psi= 0.54, (SE= 0.13) and declined to nearly zero at stations with the highest amounts of human activity. Bobcats, coyotes and gray fox were also ubiquitous, and used sites with high human activity, including active roads. Coyote and human detections were moderately correlated (r =0.41), and coyotes readily used active roads (psi=1). Jaguars, ocelots and pumas exhibited patterns of use farther from high human activity, indicating the potential for human impacts on the spatial distribution and abundance of these species inhuman-fragmented landscapes.