The Herpetological Journal

Authors: Camilo Alejandro Cruz-Arroyave, Carlos A. Yáñez-Arenas, Jaime Zúñiga-Vega & Hibraim A. Pérez-Mendoza

Abstract: Understanding the spatial distribution of fossorial snakes remains challenging due to their cryptic nature and low detectability, hindering conservation efforts for these threatened species. We used single-season occupancy models to identify fine-scale ecological drivers of distribution and detectability for Conopsis lineata, a fossorial snake endemic to central Mexico and threatened by urban expansion. Between May and October 2024, we surveyed 30 transects in the south of Mexico City, recording 36 individuals across 137 surveys. Our results revealed that detectability increased with the number of natural cover objects and decreased with maximum microhabitat temperatures above 30 °C, whilst occupancy was strongly associated with terrain slope, with snakes restricted to sites with slopes below 30 °. Contrary to expectations, snakes did not preferentially select microhabitats within their reported preferred temperature range (22–30 °C), with 61% of individuals found at cooler temperatures, suggesting that thermal selection may be constrained by predation risk or temporal availability of suitable temperatures under cover objects. Occupancy was better predicted by geomorphological features (maximum slope) than by vegetation characteristics or bioclimatic variables, supporting the scale domain hypothesis by empirical evaluation at fine-scale and supporting a previously reported association between fossorial snakes and flat terrain. This relationship is particularly concerning as low-slope areas in Mexico face intense pressure from urbanisation and agriculture. Our findings demonstrate that accounting for imperfect detection is crucial for understanding fossorial snake ecology and that terrain slope represents a key yet overlooked factor in their spatial distribution. These results provide actionable insights for conservation planning and sampling design for cryptic species, highlighting the urgent need for targeted environmental education campaigns in rural communities where human-snake encounters frequently result in snake mortality.

Keywords: occupancy, microhabitat use, imperfect detection, cryptic species, urbanisation, slope