Spatial capture-recapture and LiDAR-derived vegetation metrics reveal high densities of ocelots on Texas ranchlands

Abstract

Reliable estimates of population density and size are crucial to wildlife conservation, particularly in the context of the Endangered Species Act. In the United States, ocelots (Leopardus pardalis pardalis) were listed as endangered in 1982, and to date, only one population density estimate has been reported in Texas. In this study, we integrated vegetation metrics derived from LiDAR and spatial capture-recapture models to discern factors of ocelot encounter rates and estimated localized population estimates on private ranchlands in coastal southern Texas. From September 2020 to May 2021, we conducted a camera trap study across 42 camera stations on the East Foundation’s El Sauz Ranch, which was positioned within a larger region of highly suitable woody and herbaceous cover for ocelots. We observed a high density of ocelots (17.6 ocelots/100 km2) and a population size of 36.3 ocelots (95% CI: 26.1–58.6) with the 206.25 km2 state space area of habitat. The encounter probability of ocelots increased with greater canopy cover at 1-2 m height and decreasing proximity to woody cover. These results suggest that the incorporation of LiDAR-derived vegetative canopy metrics allowed us to understand where ocelots are likely to be detected, which may aid in current and future population monitoring efforts. These population estimates reflect the first spatially explicit and most recent estimates in a portion of the northernmost population of ocelots in southern Texas. This study further demonstrates the importance of private working lands for the recovery of ocelots in Texas.

Selection in the third dimension: Using LiDAR derived canopy metrics to assess individual and population‐level habitat partitioning of ocelots, bobcats, and coyotes

“…We found consistent selection among ocelots for dense vegetation 0–2 m in height, supporting the idea that ocelots strongly select for dense thornshrub cover (Horne et al., 2009; Jackson et al., 2005; Sergeyev et al., n.d.). While Shindle and Tewes (1998) suggested a minimum of 2 m canopy height to be considered ideal habitat for ocelots, our results emphasize a strong selection for lower story vegetation, likely to allow for denning (Laack et al., 2005), resting, foraging or movement forays (Lombardi et al., 2022; Sergeyev et al., 2022). We observed selection for areas of greater percent vertical canopy cover throughout the diel cycle, supporting prior findings of ocelots selecting dense canopy cover (Horne et al., 2009; Sergeyev et al., n.d.; Sergeyev et al., 2022; Shindle & Tewes, 1998).…”

“…There are diverse woody communities in these areas across different seral stages. This region contains the largest patches of native woody cover along the southern Texas Gulf Coast (Lombardi, Perotto‐Baldivieso, et al., 2020) and canopy structure within these patches varies along a north‐to‐south gradient (Lombardi et al., 2022). In the northern parts of the study area, live oak ( Quercus virginiana ; 18–24 m height) is the dominant tree species, often reaching climax seral stages in different portions of the study area.…”

“…The understory of live oak forest ranges from open‐ to closed‐canopy thornshrub species such as lime prickly ash ( Zanthoxylum fagara ; 6–7 m height) and huisache ( Acacia farnesiana ; 8–9 m height), stands of palm ( Sabal spp. ), and invasive guinea grass ( Megathyrsus maximus ; 1–3 m height; Lombardi et al., 2022). However, closed‐canopy live oak forests are characterized by open understories, with palms, and other shade‐tolerant woody and herbaceous plant species and are often located near parabolic inland dunes (>30 m height).…”

“…In the southern portion of the study area, the habitat transitions to primarily mesquite ( Neltuma glandulosa ), huisache, lime prickly ash, and Texas ebony ( Ebenopsis ebano ; 10 m height) dry thorn forests with varying densities of guinea grass, cordgrass ( Spartina sp.) and diverse woody plant species (Lombardi et al., 2022). Similarly, closed canopy mesquite woodlands have more open understories, while open mesquite‐ebony woodlands are characterized by dense mixed woody and herbaceous cover.…”

Climate envelope modeling for ocelot conservation planning: peering inside the black box

“…Although listed as "Least Concern" by the International Union for Conservation of Nature, in the United States and Mexico, the ocelot is listed as federally endangered, and it is listed as critically endangered within several states of Brazil, as well as vulnerable in Colombia and Argentina. Consequently, there are regions within the ocelot's range that are actively implementing conservation measures for the species, including efforts to reintroduce ocelots in southern Texas (Lombardi et al, 2022) and northeastern Argentina (Donadio et al, 2022) in what is believed to be their historic range. As with any species recovery plan, identification of suitable current and future habitats is key to conservation efforts.…”