Physiological Considerations for Reptile Relocation due to Climate Change

One strategy to protect species from the dangers of climate change is to relocate them to more suitable habitats. In order to successfully relocate a species, many factors must be considered, including the physiology of the organism. Besson and Cree (2011) studied the suitability of the Orokonui Ecosanctuary as a relocation habitat for a lizard species in New Zealand, the tuatara Sphenodon punctatus. The tuatara’s native habitat in the Cook Strait of New Zealand is threatened by the rising temperatures of climate change. The researchers evaluated the potential of successful relocation of the tuatara to the cooler habitat in Orokonui by comparing its preferred body temperature, feeding behaviors in cooler temperatures, and critical thermal minimum to three lizards that currently inhabit the area. The results showed that the tuatara responded to the three tests similarly to the other three lizards, indicating that the tuatara may be able to successfully relocate to the Orokonui Ecosanctuary and escape the dangerous effects of climate change in their current habitat. — Isabelle Heilman

Besson, A.A., Cree, A., 2011. Integrating physiology into conservation: an approach to help guide translocations of a rare reptile in a warming environment. Animal Conservation 1, 28-37.

Rising global temperatures caused by climate change are making current habitats unsuitable for a variety of species. One lizard species in New Zealand, the tuatara Sphendon punctatus, is threatened by climate change. It has been proposed to move this species from its current habitat on the Cook Strait islands in northern New Zealand to the Orokonui Ecosanctuary in the southeast, which has a cooler climate by 3–4ºC. The researchers measured the suitability of this new habitat by comparing responses to colder temperature in feeding behaviors, the critical thermal minimum, and preferred body temperature of the tuatara to three lizard species, common geckos, jewelled geckos, and McCann’s skinks, which already inhabit Orokonui. The results demonstrated that the tuatara would likely be able to survive in the cooler temperatures of the new habitat.

The researchers used ten juvenile tuatara, thirteen common geckos, fourteen McCann’s skinks, and ten jewelled geckos in their experiment. Each species became accustomed to the laboratory habitat and schedule over a period of at least four months before the experiment began. To test the effect of cooler temperature on feeding behavior, the lizards were fed mealworms at 20º, 15º, and 5ºC to simulate autumn and winter temperatures. To prepare before each temperature session, the lizards were not fed during one week and given access to a heat lamp to accelerate digestion. Once the mealworm was given to the lizards, the authors observed the time between the introduction and apprehension of the worm (prey catching), first apprehension and swallowing of the worm (prey handling), and swallowing and appearance of the plastic tag inserted into the mealworm in the lizard’s feces (gut passage). After observing these behaviors at all three temperatures, the lizards were placed in an incubator and cooled at 1º C per hour. This continued until the lizards reached a temperature where they lost control of their muscles, which was the critical temperature minimum (CTM). The researchers then increased the temperature in the laboratory to simulate summer temperatures. The lizards were presented with a temperature gradient and their temperature selections were measured four times within every 24 hour period.

The effects of temperature on feeding behavior were measured using a linear mixed effect test, where the temperature and species were fixed factors and the three feeding activities were dependent variables. CTM of each species was analyzed using a Kruskal-Wallis test. Repeated measures ANOVA tests were used for the preferred temperature data. These analyses revealed that as the temperature decreased so did food consumption in the lizards. However, temperature affected each feeding behavior differently. Prey catching time increased with temperature across all species. Increases in prey handling time were most obvious between the 12º and 5ºC temperatures sets, but decreased over all the temperature sets. Gut passage time was affected by both temperature and species, although all species had slower gut passage times or a lack of feces as the temperature got cooler. CTM was significantly different for each species; however the CTM of tuatara was similar to that of the two gecko species. Preferred body temperature was similar among the four species, with all four preferring the 20º to 27ºC temperature range.

The results of the statistical tests demonstrate enough similarities between the tuatara and the three lizard species to signify that the tuatara could be able to live in the cooler Orokonui habitat. However, this experiment also demonstrated a possible limitation for their survival in colder temperatures. The tuataras were unable to digest the mealworms at 5ºC without the help of a heat lamp. In their natural habitat, tuatara bask in the sun to aid in digestion, yet the Orokonui habitat has limited basking space, which could be problematic for the tuatara to complete digestion. To combat this danger, the tuatara could increase basking time when the temperature is warm enough.

Overall, the authors found that the relocation of tuatara from the islands of Cook Strait to Orokonui Island could be possible. The feeding responses at cooler temperatures, CTM, and preferred body temperature of the tuatara were similar to that of the common gecko, jewelled gecko, and McCann’s skink which currently inhabit Orokonui. This experiment demonstrates the importance of considering physiological factors of species when finding an area for relocation to avoid the dangerous effects of climate change.

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