Abstract
Global climate change is already contributing to the extirpation of
numerous species worldwide, and sensitive species will continue to face
challenges associated with rising temperatures throughout this century
and beyond. It is especially important to evaluate the thermal ecology
of endangered ectotherm species now so that mitigation measures can be
taken as early as possible. A recent study of the thermal ecology of the
federally endangered Blunt-Nosed Leopard Lizard (Gambelia sila)
suggested that they face major activity restrictions due to thermal
constraints in their desert habitat, but that large shade-providing
shrubs act as thermal buffers to allow them to maintain surface activity
without overheating. We replicated this study and also included a
population of G. sila with no access to large shrubs to facilitate
comparison of the thermal ecology of G. sila in shrubless and shrubbed
populations. We found that G. sila without access to shrubs spent more
time sheltering inside rodent burrows than lizards with access to
shrubs, especially during the hot summer months. Lizards from a shrubbed
population had higher midday body temperatures and therefore poorer
thermoregulatory accuracy than G. sila from a shrubless population,
suggesting that greater surface activity may represent a
thermoregulatory tradeoff for G. sila. Lizards at both sites are
currently constrained from using open, sunny microhabitats for much of
the day during their short active seasons, and our projections suggest
that climate change will exacerbate these restrictions and force G. sila
to use rodent burrows for shelter even more than they do now, especially
at sites without access to shrubs. The continued management of shrubs
and of burrowing rodents at G. sila sites is therefore essential to the
survival of this endangered species.