Texas Tortoises (Gopherus berlandieri) are understudied compared to federally protected congeners. Despite important early studies on the basic ecology of G. berlandieri, quantitative identification of habitat associations with specific environmental conditions has been limited. Gopherus berlandieri inhabits Tamaulipan thornscrub across its range, and coastal populations are historically associated with low-relief clay ridges with thick mesquital scrub surrounded by salt prairie grasslands. Our study examined tortoise home range size and association with canopy cover and potential ground moisture at a protected natural area in Cameron County, TX, USA. Twelve tortoises were outfitted with GPS loggers that recorded location once an hour from March 2020 to March 2022. To delineate home ranges, we estimated utilization distributions (UDs) for tortoises as autocorrelated kernel density estimates (AKDEs) at low-use (95%) and core-use (50%) levels for each tortoise. UDs were estimated for the entire study period and during seasons of sustained heat or cold to determine if tortoises used space differently across these seasons over the study period. Applying a use-availability study design, we compared canopy cover and potential mesic ground condition (i.e., precipitation flow accumulation) within each tortoise’s UD (‘‘use’’) to the area within 1 day’s movement around the boundary of the UD (‘‘available’’). Tortoise UD sizes were significantly different across seasons for low-use (95%) but not for core-use (50%) AKDE levels. Tortoise UDs had greater canopy cover compared to available-but-unused areas at both AKDE levels. Potential mesic ground condition did not significantly differ between available and used areas. Our study revealed that tortoises vary the size of their home ranges throughout the year, whereas areas of intensive use or occupation tended to remain remarkably stable throughout the year. In seasons of extreme weather (hot or cold), tortoises seem to seek out areas of denser canopy cover that likely serve as thermal refugia. Based on our results, effective habitat identification may best be served by ensuring that canopy cover is at least equivalent to the values reported here to ensure sufficient refugia during extreme seasonal temperatures.

Guerra DA, Esque TC, Davis DR, Veech JA. 2025. Home range, seasonality, and the importance of canopy cover for Texas tortoises (Gopherus berlandieri). Herpetologica 81:224–235. [PDF]

Many amphibian species have declined throughout their ranges, and often the causes of those declines are poorly understood . Large-scale amphibian declines were first observed in the 1970s, and in the following decades, Batrachochytrium dendrobatidis (Bd) infection was determined as the cause of some of these declines . Retrospective studies allow us to evaluate historical disease patterns and are particularly valuable in species that are extirpated or extinct. The Black-spotted Newt (Notophthalmus meridionalis; Salamandridae) is an understudied species of salamander native to south Texas, USA, and northeastern Mexico that has shown alarming population declines over the past 70 years, most notably prior to 1980. Notophthalmus meridionalis has disappeared from the northern part of its range in recent decades. Multiple factors have likely contributed to its decline, including habitat loss, habitat fragmentation, and pesticide use. In the past century, the majority of native habitat in south Texas has been cleared for agriculture, urbanization, and roads, leaving small patches of fragmented habitat remaining across the species’ historical northern range. However, declines in N. meridionalis have also been observed in protected areas not affected by habitat loss and degradation. The reason for their disappearance from these areas is unknown, raising the question of whether Bd infections were contributing to their decline. Here, we assayed 314 N. meridionalis museum specimens to determine whether the historical presence of Bd may have contributed to population declines in this species.