BioGecko Issue 2 (October 2014)

Knox, Carey 2014. Tail loss as an indicator for predation pressure on Naultinus populations. BioGecko, October 2014, 2: 29-30.



Tail loss as an indicator for predation pressure on Naultinus populations.

Abstract: I examined data on tail loss, or autotomy, in jewelled geckos (Naultinus gemmeus). This data was collected over four years of surveys on Otago Peninsula, South Island, New Zealand. Individual geckos were identified based on their individually unique dorsal patterns and monitored through time. I looked at relationships between the presence or absence of livestock grazing, habitat composition and the incidence of tail loss in jewelled geckos. In addition, I compared incidents of tail loss between Otago Peninsula and a mammal predator-free site at Orokonui Ecosanctuary. Two habitats were examined: Coprosma spp. shrubland and kānuka dominated forest. I predicted that the incidence of tail loss would be higher at ungrazed sites in both habitats, due to an assumed higher density of rodent and mustelid predators. In ungrazed Coprosma shrubland, a significantly higher incidence of tail loss in jewelled geckos (compared to grazed Coprosma shrubland) was observed. In contrast, grazing appeared to have no significant effect on the incidence of tail loss in kānuka. No tail loss was recorded at Orokonui Ecosanctuary. These results are interpreted, including an assessment of all other possible causes of tail loss in jewelled geckos. This assessment supports the contention that tail loss frequencies may provide a coarse measure of predation pressure on Naultinus geckos. This research adds to growing evidence which suggests that predation by pest mammals can be a significant threat to lizard populations living in fragmented shrubland with abundant rank grasses.


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