Social Networking of the Otago Skink (Oligosoma otagense) at Ōrokonui Ecosanctuary

Abstract

The social behaviour of New Zealand’s native lizards is poorly understood. This study explores the social behaviour of the Otago skink (Oligosoma otagense), one of New Zealand’s largest-bodied and rarest species of lizards. The Otago skink has previously been observed in pairs and groups, but little else is known about its social behaviour. This study was conducted on a translocated population inhabiting an enclosure at Ōrokonui Ecosanctuary.

In order to gain a better understanding of the social behaviour of these lizards, this research aimed to compare the stability of interactions over time. Regular photo surveys of solitary and non-solitary animals were conducted from April to October 2018, and this time period was split into two seasons. Social network analysis was then used to determine the pairwise measure of interactions of the 33 skinks in the enclosure. This study showed the presence of stability in the overall social structure of Otago skinks at Ōrokonui Ecosanctuary. When juvenile interactions were taken out of the network, there was a significant relationship between the interactions observed in seasons 1 and 2, thus indicating stable interactions between adults and subadults. Juveniles, on the other hand, showed no stability in their interaction patterns. The presence of stability between networks can therefore be attributed to interactions formed by adult and subadult Otago skinks. In addition, aggression was also observed in the population. However, there was no significant relationship between the aggression seen in season 1 and the aggression seen in season 2.

The second aim of the research was to analyse the composition of social interactions, and in particular, to determine whether social interactions were based on family relationships. Genotyping was conducted on tail tissue obtained from six subadults and two juveniles, and 15 loci were isolated and amplified from these tissue samples. From this small sample size which was not inclusive of adults, there was a trend for related individuals to be more likely to interact with one another, as opposed to individuals that were not related. However, there was no significant relationship between interaction patterns and genetic relatedness among the eight skinks.

The study finally looked at the effects that operative environmental temperatures (Te) had on aggregation. Copper models with internal temperature data loggers were used to measure the rock surface temperature of the tors at the time when skinks were observed. The Te was then compared against whether skinks were seen aggregating or not aggregating. No significant relationship was detected between Te and aggregation.

Overall, this study has provided a deeper understanding on the social behaviour of the Otago skink. Sociality in Otago skinks has, for the first-time, been observed for as long as six months. The study has also revealed the presence of stability in the Otago skink population at Ōrokonui Ecosanctuary. This means that care must be taken for prospective conservation management strategies as artificially altering the social structure may potentially impact the fitness of these lizards. Therefore, a better insight into the social networking of Otago skinks, as well as their movements and habitat, will provide invaluable information for successful future translocations of existing natural populations, and better conservation management strategies for this endangered species.