Density-dependence in the mating system of tuatara, threatened reptiles of New Zealand
The mating system of species can affect persistence, especially in small populations. Translocations as conservation techniques usually result in small starting populations, hence confirming matings and comparing the mating system with the parent population are important measures of interim success. Tuatara, threatened reptiles of New Zealand, were translocated from a natural population on Stephens Island to the Karori Wildlife Sanctuary (KWS), a mainland island of natural habitat surrounded by a mammal-proof fence. On Stephens Island the population density is 2000 tuatara per hectare and at the KWS the density is 60/ha. Both populations are in a 1:1 sex ratio, however male tuatara are able to mate every year, and females only mate, on average, every four years. The high density of tuatara on Stephens Island results in territorial disputes to obtain access to mates. Territories are larger and more widely dispersed in the translocated population. We estimate only about ten females in the translocated population are receptive to mating this season. We observed tuatara throughout the month long mating season between 2 and 8pm daily. Females were observed rejecting males, mating with more than one male, and repeatedly mating with the same male. To assess the interim success of the translcoated population and compare the mating systems between populations we will observe nesting, and confirm paternity of offspring using molecular techniques to establish the number of males contributing to the genetic diversity of the starting population.