Do #pitvipers voluntarily tolerate heat in captivity as they do in the wild?
Updated: Dec 31, 2020
This text was adapted from Díaz-Ricaurte and Serrano 2020.
Apparently, YES - and this might have important methodological and ecological implications!
Most studies on upper thermal limits focus on critical temperatures, which is the last thermal threshold before death, and fails to include the animal’s own perception of thermal stress. However, animals rarely reach that threshold since they are able to thermoregulate by moving to colder sites.
Thus, Behavioral Thermal Tolerance indexes are essential to better understand how upper temperatures might affect their thermoregulation performance.
Furthermore, most studies test animals in laboratory conditions but fail to consider how thermal tolerance changes in captivity and how these experiments translate to on-field natural conditions.
In our work, we have shown that Behavioral Thermal Tolerance does not change throughout a short-term captivity period, in spite of noticeable inter-individual variation. These differences in interindividual thermal tolerance, albeit small, might be important for population dynamics.
Bothrops pauloensis occurs in Cerrado open dry savannas, with both high (up to 35–37°C in the study area, pers. obs.) and highly variable environmental temperatures. This requires it to have behavioral (e.g., occupying burrows) and physiological thermoregulatory strategies that allow its populations to survive and persist. Thermal tolerance has been shown to depend on previous thermal
history, such that ectotherms withstand higher temperatures after short periods of exposure to nonlethal temperatures.
This was not the case of B. pauloensis, whose thermal tolerance did not increase after exposure to their voluntary thermal maximum (VTMax). Our observations seem to indicate low phenotypic plasticity in this population of B. pauloensis as they do not appear to adjust their tolerance to higher temperatures, at least for short‐term periods after exposure to VTMax.
Studies with snake species are usually limited by the difficulty of finding individuals and our study reflects a comprehensive sampling effort over a 2‐year period and thus a reasonably representative sample of this population. Thus, as our results are the first estimates of behavioral thermal tolerance in neotropical snakes, our findings can be a baseline for tests with larger sample sizes aiming to understand ectotherm thermal tolerances.
Thus, we encourage future studies to estimate behavioral thermal tolerances to improve understanding of the vulnerability of these species to future global warming. We also hope this study promotes future observations on thermal ecology and the impact of
captivity on ectotherms, especially neotropical snakes.
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Text by Juan C. Díaz Ricaurte
Díaz-Ricaurte, JC; Serrano F. Short-term captivity does not affect immediate voluntary thermal maximum of a Neotropical pitviper: implications for thermoregulation. Journal of Experimental Zoology Part-A Ecological and Integrative Physiology, 1–8. LINK