Fire management alters the thermal landscape and provides multi‐scale thermal options for a terrestrial turtle facing a changing climate

Abstract

As effects of climate change intensify, there is a growing need to understand the thermal properties of landscapes and their influence on wildlife. A key thermal property of landscapes is vegetation structure and composition. Management approaches can alter vegetation and consequently the thermal landscape, potentially resulting in underappreciated consequences for wildlife thermoregulation. Consideration of spatial scale can clarify how management overlaid onto existing vegetation patterns affects thermal properties of landscapes relevant to wildlife. We examined effects of temperature, fire management, and vegetation structure on multi-scale habitat selection of an ectothermic vertebrate (the turtle Terrapene carolina triunguis) in the Great Plains of the central United States by linking time-since-fire data from 18 experimental burn plots to turtle telemetry locations and thermal and vegetation height data. Within three 60-ha experimental landscapes, each containing six 10-ha sub-blocks that are periodically burned, we found that turtles select time-since-fire gradients differently depending on maximum daily ambient temperature. At moderate temperatures, turtles selected sub-blocks with recent (<1 year) time-since-fire, but during relatively hot and cool conditions, they selected sub-blocks with later (2-3 year) time-since-fire that provided thermal buffering compared with recently burned sub-blocks. Within 10-ha sub-blocks, turtles selected locations with taller vegetation during warmer conditions that provided thermal buffering. Thermal performance curves revealed that turtle activity declined as temperatures exceeded ~24-29°C, and on "heat days" (≥29°C) 73% of turtles were inactive compared with 37% on non-heat days, emphasizing that thermal extremes may lead to opportunity costs (i.e., foregone benefits turtles could otherwise accrue if active). Our results indicate that management approaches that promote a mosaic of vegetation heights, like spatiotemporally dynamic fire, can provide thermal refuges at multiple spatial scales and thus be an actionable way to provide wildlife with multiple thermal options in the context of ongoing and future climate change.

Avoiding mortality: timing prescribed burns in ornate box turtle habitat

“…As such, future research should monitor summer turtle activity patterns and integrate turtle behavior during high temperatures into models. For example, the activity of three‐toed box turtles ( T. c. triunguis ) is reduced at temperatures >29°C (Robertson et al 2022), so there may be temperatures when ornate box turtles return underground to avoid particularly hot conditions. By identifying the conditions influencing the activity of threatened wildlife in prairie fragments, land managers can make biological decisions about timing prescribed burns.…”

Effects of Prairie Degradation and Restoration on Box Turtle Thermal Ecology

“…Preferred body temperatures of T. ornata (29°C) and T. carolina (27°C), as determined by lab trials in do Amaral et al (2002), are well below any of the operative temperatures measured in degraded habitat during the 1200 h and 1600 h time points (Legler, 1960). This suggests that thermal conditions available in degraded prairie severely restrict the daily available activity windows of these species, leading to decreases in foraging opportunities, mate searching, and breeding activities (Grant and Dunham, 1988; Robertson et al, 2021). Although degraded prairie habitat structure is superficially similar to restored prairie habitat, degraded habitat does not provide the thermal heterogeneity among microhabitats necessary for box turtles to thermoregulate efficiently or shelter from extreme temperatures.…”

“…Our observations of selection for more-open, warmer microhabitats by T. ornata support past observations of behavioral differences between the species (Stone and Moll, 2009). However, canopy cover intrusion and inadequate prescribed burning could allow T. carolina to invade landscapes that would otherwise be unsuitable for this species (Reagan, 1974; Robertson et al, 2021). Mesic conditions in degraded prairie with woody plant encroachment might allow for increased competition and hybridization between T. carolina and T. ornata (Cureton et al, 2011).…”

Assessing impacts of climate change on selected foundation species and ecosystem services in the South‐Central USA

“…due to habitat loss. However, for many species, escape to areas of opportunity is further threatened by climate change that will have a compounding effect (land fragmentation × climate change) that reduces such areas (Robertson et al, 2021). We describe this compounding effect in all the examples presented in this paper, but similar scenarios are possible in other grasslands and savannas worldwide (Staver et al, 2011; Stevens et al, 2017).…”