Thermal plasticity in young snakes: how will climate change affect the thermoregulatory tactics of ectotherms?

Abstract

SUMMARYClimate change will result in some areas becoming warmer and others cooler, and will amplify the magnitude of year-to-year thermal variation in many areas. How will such changes affect animals that rely on ambient thermal heterogeneity to behaviourally regulate their body temperatures? To explore this question, we raised 43 captive-born tiger snakes Notechis scutatus in enclosures that provided cold (19-22°C), intermediate (19-26°C) or hot (19-37°C) thermal gradients. The snakes adjusted their diel timing of thermoregulatory behaviour so effectively that when tested 14 months later, body temperatures (mean and maximum), locomotor speeds and anti-predator behaviours did not differ among treatment groups. Thus, the young snakes modified their behaviour to compensate for restricted thermal opportunities. Then, we suddenly shifted ambient conditions to mimic year-to-year variation. In contrast to the earlier plasticity, snakes failed to adjust to this change, e.g. snakes raised at cooler treatments but then shifted to hot conditions showed a higher mean body temperature for at least two months after the onset of the new thermal regime. Hence, thermal conditions experienced early in life influenced subsequent thermoregulatory tactics; the mean selected temperature of a snake depended more upon its prior raising conditions than upon its current thermoregulatory opportunities. Behavioural plasticity thus allows snakes to adjust to suboptimal thermal conditions but this plasticity is limited. The major thermoregulatory challenge from global climate change may not be the shift in mean values (to which our young snakes adjusted) but the increased year-to-year variation (with which our snakes proved less able to deal).

Cold-induced mortality of invasive Burmese pythons in south Florida

“…In some snakes, thermoregulatory and other behavioral tactics appear to be set early in life, and exposure to novel thermal or habitat conditions later in ontogeny can provoke maladaptive behaviors (Kingsbury and Attum 2009;Aubret and Shine 2009). The python population in south Florida has probably not previously experienced such cold temperatures as those in early 2010; thus the population may be thermally naïve, providing an alternative hypothesis for observations of cold-induced mortality.…”

Cold weather and the potential range of invasive Burmese pythons

“…Nevertheless, a potentially significant consequence of the lack of genetic variation among the south Florida pythons may be reduced behavioral and ecological flexibility, with a resultant inability to adapt to significant changes in climatic conditions. Moreover, Aubret and Shine (2010) concluded that snakes' thermoregulatory tactics are based more in the conditions of their raising than their current thermoregulatory opportunities, thus making year-toyear temperature variation their major thermoregulatory challenge for survival.…”

Can invasive Burmese pythons inhabit temperate regions of the southeastern United States?

“…Little is known about the genetics of Florida pythons or their origins, but the species has been imported in large numbers from tropical regions of southeast Asia in the past (Reed 2005). Recent experiments on Australian Tiger Snakes (Notechis scutatus) demonstrated that snakes raised in one thermal environment adopt inappropriate thermoregulatory behaviors and fail to maintain preferred T b 's after an environmental shift (Aubret and Shine 2010). Thus, alternatively, the pythons we tested, which were all from southern Florida and at least 1.5 years old, may have been acclimatized to the warmer environmental conditions they experienced when young, prompting them to behave inappropriately when confronted with colder conditions in South Carolina.…”