ESTIMATING THE HOME-RANGE AND CARRYING-CAPACITY FOR TAKAHE (PORPHYRIO-MANTELLI) ON PREDATOR-FREE OFFSHORE ISLANDS - IMPLICATIONS FOR FUTUREMANAGEMENT

Predator-free offshore islands play an important role in the conservat ion of many of New Zealand's endemic species. Takahe (Porphyrio mantel li) have small populations established on four offshore islands and al though hatching success is lower than that of the wild mainland popula tion in Fiordland, juvenile and adult survival is high and populations are growing exponentially. Accurate estimates of home range size and potential carrying capacities are therefore essential for the future m anagement of the population as a whole. The mean home range size of ta kahe pairs in one study population on Mana Island (217 ha) was 2.8 +/- 1.9 ha. The island was assessed for current and maximum available are a for takahe and the potential carrying capacity was estimated at 22 - 53 pairs. Current and maximum available areas were also used to calcu late carrying capacities on each of three other islands using two diff erent estimates of mean home range size for Maud Island (7 - 34 pairs) and Kapiti Island (5 - 33 pairs) and one estimate of home range size for Tiritiri Matangi Island (25 pairs). A model of the population grow th of takahe on islands predicted that estimated carrying capacities w ould be reached between 1997 and 2009. The urgency of planning to make use of the considerable potential of island populations of takahe is stressed.