Natural history of the spot-tailed earless lizards (Holbrookia lacerata and H. subcaudalis)

Authors: Toby J. Hibbitts, Danielle K. Walkup, Travis J. LaDuc, Brad D. Wolaver, Jon Paul Pierre, Mike Duran, Dalton Neuharth, Shelby Frizzell, Connor S. Adams, Timothy E. Johnson, Danny Yandell, and Wade A. Ryberg

The conservation of rarely encountered species is notoriously difficult mainly because of the lack of information about their natural history. This is definitely the case for the spot-tailed earless lizards (Holbrookia lacerata and H. subcaudalis). Sparse distributional records and infrequent observations at known sites were used as evidence to petition these species for protection under the Endangered Species Act. For this study, we did surveys in historic and new areas to determine the current distribution of both species. We also radio-tracked individuals from two populations to estimate movement potential and home range sizes, as well as understand habitat use. Distribution surveys indicate that H. lacerata has undergone range contraction (39%); however,
H. subcaudalis was historically found in 21 counties but we only observed them in five. We found home ranges to be relatively large compared to similarly sized insectivores and at least four times larger than the similar H. maculata. Both species are inhabitants of historic grasslands, but within this habitat type they used sites that were more open compared to what was available, including areas such as row-crop agriculture and frequently mowed fields. Frequent habitat disturbance seems to be important for both species. Urbanisation, invasive woody vegetation and invasive grasses are all considered threats that may have already caused declines to both species.

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