Establishment, Dispersal and Population Viability of Translocated Duvaucel's Gecko (Hoplodactylus Duvaucelii) on Mana Island

Abstract

Duvaucel's gecko (Hoplodactylus duvaucelii) is New Zealand's largest extant gecko and currently has a relict distribution similar to the tuatara (Sphenodon). Post-release monitoring of a population of H. duvaucelii translocated from North Brother Island to Mana Island in 1998 was undertaken. From this the population's establishment and dispersal were assessed and its long term viability analysed. The ecological restoration of Mana Island requires the re-establishment of previously resident communities. Reptile assemblages would have been an important component of the island's ecosystem, and as only four out of seven reptile species represented in middens have remained, the reintroduction of the absent species is necessary. In 1998 40 H. duvaucelii were transferred to Mana Island from North Brother Island in two translocations of twenty-one and nineteen individuals respectively (in February and November). Post-release monitoring using four different techniques gave recapture data for only seven individuals (five adult females and two subadults). The results obtained from these recaptures gave little indication as to the success of the translocation, but provided some evidence of breeding and growth. Individuals seem to have dispersed in all directions from their release sites, but the data set was too small to provide any home range information. Establishment cannot be confirmed as successful until the estimated population size exceeds the number of individuals released and at least half the population is Mana Island-born. It is suggested that the population will not be large enough for a significant number of individuals to be recaptured until ten years after the initial release. Viability analysis, using the computer program VORTEX, predicts the long term survival of this population even under the effects of environmental variation and catastrophes. However, a more realistic model cannot be produced until additional information is available for the Mana Island population.