Evaluating population connectivity and targeting conservation action for an endangered cat

Abstract

Dispersal of animals among populations helps to increase genetic variability and population viability. The endangered ocelot (Leopardus pardalis) in south Texas persists in two small populations separated by 30 km and cutoff from populations in northeastern Mexico. Despite the relatively short distance separating the two south Texas populations, movement between them has been limited, leading researchers to believe landscape connectivity is poor in the region. We developed habitat suitability maps using remote sensing and GPS-collared ocelots and ran connectivity analyses to assess current habitat linkages, important areas for conservation, and areas where connectivity could be improved through habitat restoration. First, we developed a resource selection function using random forest models and GPS data from ten ocelots collared at Laguna Atascosa National Wildlife Refuge combined with spatial layers derived from LiDAR and remotely sensed imagery. We then used these results as the basis for a cost surface layer. Using this layer, we examined habitat connectivity using least-cost and circuit theory methods. We evaluated linkages by cost of movement, identified areas important for maintaining existing connectivity, and ranked areas where restoration would have the greatest benefit to connectivity. We found that core habitats within the two populations were relatively well connected but connectivity between the two populations was poor. By identifying areas currently important for connectivity and areas with the greatest benefit to ocelots if restored, these results will help inform land acquisition and restoration planning to improve ocelot conservation in south Texas.

Landscape Structure of Woody Cover Patches for Endangered Ocelots in Southern Texas

“…These results contradict findings by Haines et al [36] and more recently Lehnen et al [40]) in southern Texas. Haines et al [36] predicted 11 patches of suitable habitat in the areas where ocelots are known to exist, based solely on canopy cover.…”

“…Haines et al [36] predicted 11 patches of suitable habitat in the areas where ocelots are known to exist, based solely on canopy cover. Lehnen et al [40] used GPS data from 2012 to 2017 with coarse (50 m) resampled LiDAR and satellite imagery to predict suitability for ocelots at the second-order (home range; [63]) for each population in Texas. Each study did not account for the potential of ocelots to occur in forested cover in addition to thornshrub and used data from Laguna Atascosa National Wildlife Refuge without forested cover to extrapolate their results across larger areas.…”

“…We used Fragstats (Fragstats 4.2, [53]) to obtain landscape metrics of woody cover that have been previously shown to characterize the spatial distribution and structure of woody cover related to ocelot occurrence and space use across their geographic range (including southern Texas) (Table 1) [31][32][33][34][39][40][41]54]. We estimated the size (mean patch size [MPA; ha]), patch density (PD; the number of patches/100 ha), and complexity of woody cover patches (landscape shape index (LSI), which yield an index of patch fragmentation.…”

“…Ocelots are endangered (<80 individuals) in the United States [36,37] and exist in two populations in southern Texas. The "ranch population" occurs on large private ranchlands in Kenedy and Willacy counties with at least 80% of resident ocelots [31,38], and a smaller "refuge population" occurs on Laguna Atascosa National Wildlife Refuge in eastern Cameron County [32,36,[39][40][41]. In southern Texas, ocelots have been observed in semi-arid thornshrub communities with dense and mixed canopies, and live oak forests (Quercus virginiana) with thornshrub understories [31,[36][37][38]40,41].…”

“…The "ranch population" occurs on large private ranchlands in Kenedy and Willacy counties with at least 80% of resident ocelots [31,38], and a smaller "refuge population" occurs on Laguna Atascosa National Wildlife Refuge in eastern Cameron County [32,36,[39][40][41]. In southern Texas, ocelots have been observed in semi-arid thornshrub communities with dense and mixed canopies, and live oak forests (Quercus virginiana) with thornshrub understories [31,[36][37][38]40,41]. Population declines in southern Texas have been linked to road mortality, loss of genetic diversity, and large-scale woody cover loss in the early to mid-20th century [32,35,[42][43][44].…”