Effects of habitat suitability and minimum patch size thresholds on the assessment of landscape connectivity for jaguars in the Sierra Gorda, Mexico

Abstract

Maintaining habitat and its connectivity is a major conservation goal, especially for large carnivores. Assessments of habitat connectivity are typically based on the output of habitat suitability models to first map potential habitat, and then identify where corridors exist. This requires separating habitat from non- habitat, thus one must choose specific thresholds for both habitat suitability and the minimum patch size that can be occupied. The selection of these thresholds is often arbitrary, and the effects of threshold choice on assessments of connectivity are largely unknown. We sought to quantify how habitat-suitability and patch-size thresholds influence connectivity assessments for jaguars (Panthera onca) in the Sierra Gorda Biosphere Reserve in central Mexico. We modeled potential habitat for jaguars using the species distribution modeling algorithm Maxent, and assessed potential habitat connectivity with the landscape connectivity software Conefor Sensinode. We repeated these analyses for 45 combinations of habitat suitability based thresholds and minimum patch sizes. Our results indicated that the thresholds influenced connectivity assessments greatly, and different combinations of the two thresholds yielded vastly different map configurations of suitable habitat for jaguars. We developed an approach to identify the pair of thresholds that best matched the jaguar occurrence points based on the connectivity scores. Among the combinations that we tested, a threshold of 0.3 for habitat suitability and 2km2 for minimum patch size produced the best fit (area under the curve=0.9). Surprisingly, we found low suitable habitat for jaguars in most of the core areas of the reserve according to our best potential habitat model, but highly suitable areas in the buffer zones and just outside of the reserve. We conclude that the best and most connected potential areas for jaguar habitat are in the central eastern part of the Sierra Gorda. More broadly, landscape connectivity analyses appears to be highly sensitive to the thresholds used to identify suitable habitat, and we recommend conducting sensitivity analyses as introduced here to identify the optimal combination of thresholds.