COMPARISONS OF THE CLIMATES OF THE TWO HABITATS OF HAMILTON'S FROG (LEIOPELMA HAMILTONI (McCULLOCH))

Comparisons of climate data from the two known habitats of Leiopelma hamiltoni (a small deforested rock tumble near the summit of Stephens Island called the "frog bank" and a forest remnant on Maud Island) show that the two are remarkably similar, apart from greater extremes of temperature and humidity occurring at the open rock surface of the frog bank than on the surface of the Maud Island habitat. Furthermore, the air space between the rocks of the frog bank is significantly cooler, more humid and subject to less temperature fluctuation than the surface. The frogs, being nocturnal, shelter under these rocks during the day. This habit and the climate of the frog bank are the major factors permitting the survival of the frog on Stephens Island since the frog bank lost its forest cover. Climate data from a nearby remnant of the original forest suggest that the Stephens Island habitat would have been more suitable for frogs in its original forested form than in its present state. Although grasses and Muehlenbeckia vines are encroaching onto the frog bank and creating a more favourable micro-climate at the habitat's surface, such cover may eventually restrict the access of frogs to sheltering rock crevices.