The impacts of cattle grazing on arboreal reptiles

Abstract

Habitat disturbances, such as grazing by livestock, can have major direct and indirect impacts on the structure and complexity of both vegetation and faunal communities. Changes to habitat structure and resource availability often lead to changes in biodiversity. While the impacts of livestock grazing has been well studied in vegetation communities, fewer studies have focused on wildlife. Further, terrestrial (ground-dwelling) communities have generally been the focal group of interest, whereas the impacts of grazing on arboreal systems have often been overlooked. Arboreal reptiles are generally difficult to capture due to their cryptic nature and tendency to flee when encountered. Further, they often shelter under loose, peeling tree bark, or in hollows, making them difficult to capture without damaging their microhabitat. I implemented and used arboreal cover boards (ACBs) as artificial made from closed-cell foam cover boards to try and increase the capture rate of arboreal lizards. I tested the difference in capture success using standard visual encounter surveys (VES) and the use of arboreal cover boards as survey methods to sample small, cryptic arboreal lizards. Diurnal and nocturnal (spotlight) VES resulted in lower capture success compared to ACB surveys. While nocturnal VES showed a bias towards adult geckos, the use of ACBs captured individuals from all age classes. Further, ACBs were successful in monitoring non-target species, and even broad taxonomic groups. The use of ACBs extends beyond just a useful survey technique, but also provides the potential for long-term monitoring and restoring damaged or degraded microhabitats. Domestic livestock alter ground-level vegetation structure due to grazing, but little is known about the effects on arboreal habitats. Similarly, the effects grazing has on ground-dwelling wildlife populations has been examined to some extent, yet the potential impacts to arboreal groups have received little attention. I examined the responses of arboreal and terrestrial reptile communities and their respective habitats to domestic livestock grazing. Terrestrial reptiles were generally negatively associated with heavy grazing, as their primary habitat (ground-level) was heavily impacted. Terrestrial reptiles were strongly associated with ground-level habitat complexity, which was greatly reduced in areas with heavy grazing. Alternatively, arboreal reptiles were generally resistant to the impacts of even heavy grazing, and were positively associated with arboreal tree structures, such as peeling bark and tree hollows. While terrestrial and arboreal reptiles showed opposing trends (negative and positive association with grazing, respectively), individual species within these groups showed varied responses. I highlight the importance of retaining trees in rangelands as an overarching management guideline, as trees provide primary habitat for arboreal species, but also provide shade, leaf litter, and woody debris for terrestrial species. Two species that showed resistance…