Ontogenetic differences in behaviour of the Otago skink (Oligosoma otagense) at Ōrokonui Ecosanctuary

Abstract

Personalities of animals may demonstrate ontogenetic changes in response to a plethora of different environmental factors and experiences early in life. Understanding these ontogenetic personality changes aids in understanding how individuals tolerate, act and react to environments, conspecifics and other species throughout their lifespan. This behavioural topic remains relatively unexplored for many reptilian species. Because non-avian reptiles are such a diverse group of vertebrates in, ecology, behaviour and morphology, more research on ontogenetic personality changes is required for this class of animals. Relatively little is known about the social behaviour and personalities of the Otago skink (Oligosoma otagense), or how they differ between age-groups. This study aimed to examine (1) whether Otago skinks demonstrated repeatability of behaviours over four sample periods, and therefore have personalities, (2) whether sociality, aggression, boldness and exploration levels differed between adult, sub-adult and juvenile Otago skinks, and (3) whether temporal variation of sociality, aggression, boldness and exploration variables differed between adult, sub-adult and juvenile Otago skinks over four sample periods. This study was conducted on the translocated Otago skink population at Ōrokonui Ecosanctuary from the 15th of January until the 6th of October, 2020. Photographic surveys and behavioural assays were used to examine behaviours that represented boldness, sociality, aggression, and exploration levels of each skink. Individual repeatability was low for all measured behaviour variables (R < 0.120), with only boldness (proportion of sessions sighted in), exploration (proportion of sightings present at a favourite tor) and sociality (proportion of sightings present in a group) variables having significant repeatability estimates. Individual repeatability of the behavioural assay boldness variables were even lower (R < 0.104), and none of these low repeatabilities were significant. This therefore suggests that no personalities’ were detected for this Otago skink population, however this does not mean that they were not there. Several behaviours showed significant differences between age-groups. Adults were sighted significantly more often than juveniles in photographic surveys, suggesting that adults were bolder than juveniles. Juveniles were sighted significantly more often at the tor ii they spent the most time at and visited fewer tors compared to sub-adults and adults, suggesting that adults and sub-adults were more explorative than juveniles. Juveniles were sighted in larger social groups significantly more often than sub-adults, therefore indicating that juveniles had higher levels of sociality. Aggressive interactions were only observed in adults and sub-adults (not juveniles). This could suggest that sub-adults and adults had higher aggression levels. Overall there was little difference between the age-groups for correlation of behaviours between sample periods. Age-group had a significant effect on the temporal variation of proportion of sightings present at a favourite tor between two sample periods, where adults demonstrated increased consistency compared to sub-adults. There was also some stability in boldness and exploration behaviours over sample periods for all age-groups. Overall this study has provided new insights into how sociality, aggression, boldness and exploration levels differ between the different age-groups of Otago skinks at Ōrokonui Ecosanctuary. Juveniles were more social and less aggressive, bold and explorative than adults and sub-adults. This study has also revealed that this Otago skink population have relatively low repeatability and stability of behaviours. These findings will provide further insight into how Otago skink individuals will differ in how they act and react to different environments, situations and conspecifics at different points in their lifespan. This information may also aid in the future translocations and set-up of enclosures for the existing natural populations of this endangered species.