Changes in habitat use by lizards on a New Zealand island following removal of the introduced Pacific Rat Rattus exulans

Abstract

On Korapuki Island (Mercury Islands group, northeastern New Zealand) lizard capture frequencies increased following the removal of Pacific Rats Rattus exulans in 1986 and rabbits Oryctolagus cuniculus in 1987. This increase was dominated by diurnal Shore Skinks Oligosoma smithi. Increases in Shore Skink captures were proportionally greatest where beach particle sizes exceeded 25 cm dia (50-fold in five years). In sites where particles were large the Shore Skink population became dominated by adults. These changes in Shore Skink distribution and size were found in areas unlikely to have been either directly or indirectly affected by rabbits. The changes are therefore attributable to removal of Pacific Rats which apparently had greatest effect on lizards where interstices between rocks allowed the rats access. The selective natural recovery of Shore Skink populations on Korapuki Island indicates that the effects of Pacific Rats on island lizard faunas depends not only on the presence of refuge areas, such as rocky beaches, but also on the particle sizes within them.