Spatial structure of woody cover affects habitat use patterns of ocelots in Texas

Tyler A Campbell,Michael E Tewes,Jason V Lombardi,Humberto L Perotto-Baldivieso,Jose M Mata

doi:10.1007/s13364-020-00501-2

Tyler A Campbell, Michael E Tewes + Show 3 more

Open Access

https://doi.org/10.1007/s13364-020-00501-2

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Abstract

About 80% of the known breeding population of ocelots (Leopardus pardalis) in the USA occurs exclusively on private ranches in northern Willacy and Kenedy counties in South Texas. These private ranches support several large contiguous undisturbed patches of thornscrub, which is preferred by ocelots. Past studies have indicated ocelots in South Texas select for woody patches that contain extremely dense thornscrub (i.e., 95% canopy cover and 85% vertical cover) and require large patches of woody cover to survive. Landscape metrics have been used to explain ocelot habitat use in fragmented areas, but their application in less-fragmented rangelands is lacking. From 2011 to 2018, we used camera traps on the East Foundation’s El Sauz Ranch to assess seasonal habitat use of ocelots relative to landscape structure, configuration, and complexity and other site-level factors in South Texas. Seasonal habitat use and detection were positively influenced by larger mean patch area and lower landscape shape index values. We also observed ocelots were less likely to be detected during periods of drought and exhibited a seasonal trend in detection. Ocelots used woody patches that were larger and more regularly shaped, indicating a preference for areas with a lower degree of fragmentation across the study area. As patches become larger, they will coalesce over time and form larger woody aggregates, which will promote ocelot habitat use. Brush management needs to be strategic as patch area and shape index are a limiting factor to promote ocelot habitat use on working rangelands in South Texas. These results demonstrate the ability to use landscape metrics to discern the effects of spatial structure of vegetation communities relative to ocelot occupancy parameters.

Highlights

About 80% of the known breeding population of ocelots (Leopardus pardalis) in the USA occurs exclusively on private ranches in northern Willacy and Kenedy counties in South Texas
Statistical approaches like occupancy modeling have become a useful technique for discerning species occurrence or habitat use at different temporal and spatial scales (Wang et al 2019). This statistical approach combined with robust long-term camera trap monitoring datasets, landscape metrics, and other site-level factors can aid in elucidating potential thresholds of habitat use and help guide recovery strategies, land stewardship, and management decisionmaking (Crooks 2002; Zemanova et al 2017)
We placed a 500-m buffer around each camera site and we examined six class-level metrics to quantify the spatial structure of woody and herbaceous cover types using Fragstats 4.2 (McGarigal et al 2015): patch density (PD; number of patches/100 ha), landscape shape index (LSI), mean patch area (MPA; ha), percent landscape (PLAND; %), Euclidean distance to nearest neighbor (ENN; m), and edge density (ED; m/ha) (Perotto-Baldivieso et al 2011; Zemanova et al 2017; Lombardi et al 2020a)

Summary

Introduction

About 80% of the known breeding population of ocelots (Leopardus pardalis) in the USA occurs exclusively on private ranches in northern Willacy and Kenedy counties in South Texas. Though studies have been conducted examining ocelot habitat use patterns in fragmented landscapes, habitat use patterns in the larger working rangelands where there are likely larger patches and a greater degree of spatial heterogeneity in the structure, configuration, and complexity of woody cover are poorly known (Lombardi et al 2020b).

Results

Conclusion