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Heat and water loss vs shelter: a dilemma in thermoregulatory decision-making for a retreat-dwelling nocturnal gecko

Citation

Chukwuka, Christian; Monks, Joanne M.; Cree, Alison (2020), Heat and water loss vs shelter: a dilemma in thermoregulatory decision-making for a retreat-dwelling nocturnal gecko, Dryad, Dataset, https://doi.org/10.5061/dryad.b2rbnzsc4

Abstract

Understanding the interaction between upper voluntary thermal limit (VTmax) and water loss may aid in predicting responses of ectotherms to increasing temperatures within microhabitats. However, the temperature (VTmax) at which climate heating will force cool-climate, nocturnal lizards to abandon daytime retreats remains poorly known. Here, we developed a new laboratory protocol for determining VTmax in the retreat-dwelling, viviparous Woodworthia Otago/Southland gecko, based on escape behaviour (abandonment of heated retreat). We compared the body temperature (Tb) at VTmax, and duration of heating, between two source groups with different thermal histories, and among three reproductive groups. We also examined continuous changes in Tb (via an attached biologger) and total evaporative water loss (EWL) during heating. In the field, we measured Tb and microhabitat thermal profiles to establish whether geckos reach VTmax in nature. We found that VTmax and duration of heating varied between source groups (and thus potentially with prior thermal experience), but not among reproductive groups. Moreover, geckos reached a peak temperature slightly higher than VTmax before abandoning the retreat. Total EWL increased with increasing VTmax and with the duration of heating. In the field, pregnant geckos with attached biologgers reached VTmax temperature, and temperatures of some separately monitored microhabitats exceeded VTmax in hot weather implying that some retreats must be abandoned to avoid overheating. Our results suggest that cool-climate nocturnal lizards that inhabit daytime retreats may abandon retreats more frequently if climate warming persists, implying a trade-off between retention of originally occupied shelter and ongoing water loss due to overheating.

Methods

Data collection and processing were described in the manuscript.

Funding

Department of Zoology, University of Otago New Zealand, Award: GL.FZ.PhD_8227675

Miss E. L. Hellaby Indigenous Grassland Trust, Dunedin New Zealand, Award: 2017 Batch