Abstract
This thesis focused on evaluating the short- and long-term success of four separate translocations of jewelled gecko (Naultinus gemmeus) into and within Orokonui Ecosanctuary, Dunedin, New Zealand. The jewelled gecko is a diurnal, arboreal species of New Zealand green gecko, highly susceptible to predation, habitat loss and illegal poaching. Populations have been translocated to three sites within Orokonui ecosanctuary (from sites on the Otago Peninsula at high risk of illegal poaching) over three separate translocations that have used both penned and hard release methods. A fourth translocation of jewelled geckos (sourced from within the ecosanctuary) to Orokonui’s new jewelled gecko enclosure began in December 2020. Understanding the short and long-term implications of translocation methods used, and assessing the suitability of the release site, is essential when refining best translocation practices for a species.
Firstly, I examined the stage of translocation success (based on the criteria of Miller et al., 2014) and long-term dispersal of founders resighted at both the hard and penned jewelled gecko release sites within Orokonui Ecosanctuary. The penned release method was expected to reduce the dispersal of founder individuals long-term and therefore encourage future generations to establish at the release site. Thus, population growth (more individuals sighted than released) was predicted to be detected at the two penned release sites (released in 2009 and 2021) but not the hard release site (released in 2012). Between June 2020 and February 2021, 75 visual day surveys were conducted on sunny days when geckos were expected to be basking (equating to 392 person hours of searching). Suitable jewelled gecko habitat within a ~50 m radius of the release sites and habitat between sites were visually searched. Founders were identified through photo identification, and linear dispersal estimated. Eighty geckos were located throughout the ecosanctuary. The largest jewelled gecko population sighted was at the 2012 penned release site (40 individuals) and the smallest (10) at the 2012 hard release site. The release method used (penned versus hard release) did not have a detectable effect on the number of geckos found, the stage of translocation success reached or the distances founder individuals moved, 8-11 years following release. Evidence of population growth at the 2012 hard release and penned sites was almost confirmed (with 2-3 more sightings needed) whereas the 2009 penned release site required 14 more sightings to satisfy the criteria for population growth in Miller et al. (2014).
Secondly, I examined the suitability of Orokonui Ecosanctuary’s new jewelled gecko enclosure in terms of enabling and promoting natural behaviour. To do so, three key aspects of enclosure design were assessed: the thermal environment provided (and the thermal ecology it supports), the physical environment provided (location, habitat type, complexity and structure) and the effects of the spatial restrictions imposed (including the implications this has on home ranges and social interactions). Enclosure geckos were translocated and monitored as part of this study, between December 2020 and February 2021. The enclosure overall was predicted to be able to support ten jewelled geckos (the desired stocking density) without resulting in a loss of body condition over the 2-month study period. Thermal environments (that support natural basking behaviour) were expected to be similar between sites, however an adjustment period was predicted to be detected in gecko basking behaviour (frequency of full exposure during basking and skin temperatures reached, as geckos adjusted to their new environment and visitors circling the enclosure). All habitat within the enclosure was predicted to be used by enclosure geckos. Home ranges were predicted to be reduced as a result of the natural restrictions the enclosure imposes on gecko movements; this was expected to increase the number of interactions between geckos. Thermal environments available to geckos at the wider ecosanctuary and enclosure sites were measured using calibrated copper models, and body temperatures reached during basking were estimated with skin body temperatures captured with a thermal camera. Radiotracking was used to better understand the movements and home ranges of free-roaming geckos and information on the basking behaviour, habitat use and perch height of free-roaming and enclosure geckos was collected, and a body condition index estimated.
The enclosure’s thermal environment was significantly cooler than those at the 2009 penned and 2012 hard release sites. However, all sites enabled geckos to reach their set point temperature range (the central 50% of temperatures jewelled geckos selected when under a thermal gradient), and natural basking behaviour was observed in enclosure geckos. While the enclosure restricts individual home ranges, no aggressive interactions were observed, and body condition significantly increased over the two-month study period. These results suggest that stocking density (of eight geckos) was not an issue within the first two months following translocation. Free-roaming geckos used a wider range of habitat types than available to the enclosure geckos and free-roaming geckos occupied significantly higher perch heights than enclosure geckos. Enclosure geckos were observed using only two thirds of the suitable basking habitat available, with sightings clustered at two key points on the eastern and western sides of the enclosure and few observations made in the northern side and centre of the enclosure.
This research increases our understanding of the long-term effects penned and hard release methods have on the translocated population of jewelled geckos. There is a need however to further research the factors driving the success and failure of hard released green gecko populations to confidently determine the effect of penning green geckos on long-term establishment. This research also highlights that Orokonui Ecosanctuary’s jewelled gecko enclosure is suitable short term. Age-related increases in home range size however, are predicted, which can lead to competition and territoriality among resident geckos. Therefore future research must focus on monitoring body condition and interactions between enclosure geckos to confirm the enclosure suitability long-term.