Habitat heterogeneity affects the thermal ecology of an endangered lizard

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 populations in shrubless and shrubbed sites. 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 site had higher midday body temperatures and therefore poorer thermoregulatory accuracy than G. sila from a shrubless site, suggesting that greater surface activity may represent a thermoregulatory trade‐off 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.

Foundation plant species provide resilience and microclimatic heterogeneity in drylands

“…Numerous small animals are present within the region including the US federally endangered species Gambelia sila 76 that serves as an excellent flagship species within the state for many endangered desert species 77 . This vertebrate species and others have been shown to rely on Ephedra californica 54 , 78 .…”

“…Gradual shifts in the microclimate within a season temporally coupled with the spatial heterogeneity in the vegetation tested here likely enables ‘tiny niches’ and shifting climate-envelope matching for both plants 21 , 51 and animals—particularly ecotherms 52 , 53 . Temperature and soil moisture are but one set of many filters and capacities that we need to examine, and variability within a habitat is a resource and an asset 54 . Plants also provide other functions including carbon sequestration 9 and resources directly for animals 55 .…”

Shrub density effects on the presence of an endangered lizard of the Carrizo Plain National Monument, California

“…With more shrubs, there are likely more opportunities for positive associations as even relatively small shrub individuals provide benefits (Gaudenti et al, 2021;Lortie et al, 2018;Zuliani et al, 2021).…”

The importance of open data describing prey item species lists for endangered species

“…Key habitat characteristics include shrubs (Westphal et al, 2018), abandoned burrows (Fields et al, 1999;Prugh & Brashares, 2012) and access to habitat that provides thermal heterogeneity to support its diverse behavioural needs (Gaudenti et al, 2021;Ivey et al, 2020).…”

“…Gambelia sila or the blunt‐nosed leopard lizard was one of the first federally listed vertebrate species in the United States and is endemic to this region (Germano et al, 2011; Service, 1998). Key habitat characteristics include shrubs (Westphal et al, 2018), abandoned burrows (Fields et al, 1999; Prugh & Brashares, 2012) and access to habitat that provides thermal heterogeneity to support its diverse behavioural needs (Gaudenti et al, 2021; Ivey et al, 2020). Consequently, restoration planning for G. Sila can thus encompass many niche dimensions (Stewart et al, 2019).…”