Gopher Tortoise Demographic Responses to a Novel Disturbance Regime
Howell, Hunter J., Betsie B. Rothermel, K. Nicole White, and Christopher A. Searcy. Gopher Tortoise Demographic Responses to a Novel Disturbance Regime. The Journal of Wildlife Management 84, no. 1 (2020): 5665.
The long‐term viability of gopher tortoise (Gopherus polyphemus) populations is jeopardized by increased urbanization and habitat degradation owing to ﬁre suppression. Because the species’ remaining natural habitats in the southeastern United States exist within a mosaic of anthropogenic land uses, it is important to understand demographic responses to contrasting land uses and habitat management regimes. We examined diﬀerences in demographic parameters among ﬁre‐suppressed sandhill, restored sandhill, and former sandhill (i.e., ruderal) land use‐land cover (LULC) types at Archbold Biological Station in southcentral Florida, USA. Using Program MARK, we estimated population size, and sex‐speciﬁc and LULC‐speciﬁc survivorship based on 6 years of mark‐recapture data. We also analyzed individual growth trajectories and clutch sizes to determine whether growth rates or reproductive output diﬀered among LULC types. Tortoises in an open, ruderal ﬁeld occurred at a higher density (7.79/ha) than in adjacent restored (1.43/ha) or ﬁre‐suppressed (0.40/ha) sandhill. Despite this higher density, both adult survivorship and body size were signiﬁcantly higher in the ruderal ﬁeld. Furthermore, the larger female body size in the ruderal ﬁeld likely contributed to increased annual survivorship and slightly larger average clutch sizes. We did not detect oﬀsetting negative demographic eﬀects; in particular, we did not ﬁnd signiﬁcant biological or statistical diﬀerences in body condition, asymptotic body size, or growth rate among the 3 LULC types. Our results suggest that anthropogenic, grass‐dominated land‐cover types may be important components of the habitat mosaic currently available to this at‐risk species. © 2019 The Wildlife Society.