While employed as a postdoctoral research fellow at the University of Otago, Dr Kelly Hare looked at how captive management regimes could influence the health of individual skinks to promote more successful translocations.
The importance of captive management
In New Zealand, a large number of our native reptile species are endangered. Many of these species are restricted to mainland or offshore islands where they are safe from introduced predators. However, for many existing lizard populations in other regions, it is not possible to remove mammalian predators, and these species will always be at risk.
For some of these species, scientists are starting to create captive management options. Captive management is where individuals are kept in captivity in some sort of enclosed space. This might be in a university lab, a zoo or a research centre. It’s an important conservation tool that Kelly describes as an ‘insurance policy’ if these species become extinct on the mainland.
Optimal conditions for skinks in captivity
In her research, Kelly uses large sample sizes of the common McCann’s skink. She hopes these results can then be applied to endangered species such as the grand skink and Otago skink. Her plan is to provide guidelines for scientists and captive managers on the best husbandry regimes for keeping mothers (basking regimes) and their offspring (feeding regimes).
Skinks are ectothermic, which means that the environment regulates their body temperature (this is sometimes incorrectly referred to as ‘cold blooded’). Ectothermic animals often bask in the sun to warm up and increase their metabolism.
Kelly wanted to investigate if the amount of time spent basking under heat lamps by pregnant females influenced the number, sex, shape, size and performance of their offspring. She collected pregnant females from the wild and divided them into groups in the lab. One group received a low-basking regime of 28 hours per week, the second received basking similar to that experienced in the wild (40 hours per week), and the third was exposed to a high-basking regime of 56 hours per week.
When reptiles are kept in captivity, they are often given as much food as they want to eat. This results in fatter, faster-growing individuals. However, there is some evidence that fat individuals can’t run as quickly. Kelly is investigating whether individuals that are fatter and slower with plenty of reserves have a better chance of survival once released to the wild than those that are thinner and potentially faster.
Kelly has 3 different feeding regimes – one where the skinks are fed all the time and can eat as much as they like, another where the skinks are fed 3 times per week and a 3rd control group of wild individuals in special enclosures at Macraes Flat, Otago.
Measuring sprint speed is a research technique used by scientists to rate the performance of individuals. For example, faster skinks generally perform better in terms of escaping predators, finding mates and catching food. After the different feeding regimes, Kelly will measure the sprint speed of individuals before they are released to the wild. She will then study them for 6 months and see whether the faster ones do better in the wild (increase in size and survive) and will link this back to their feeding regime.
Kelly’s research was published in 2012. In summary she reports, "Our data indicate that, for Otago skinks, apparently negative changes in phenotype brought about by captive conditions (e.g. potential obesity and reduced speed) are not critical for their short-term survival, or ability to reproduce, where exotic predators are controlled."
The findings from the basking regime research indicate the females in the higher-basking groups have more offspring than those in the low-basking group. However, there didn’t appear to be a significant difference in the quality of offspring. These results have important implications for captive populations and suggest that, at this stage, providing plenty of opportunity for basking would increase the number of offspring born in captivity.