Plant Succession, Ecological Restoration and the Skinks of Stephens Island / Takapourewa

Ecological restoration often involves revegetation. I have investigated the impact of revegetation on the distribution, abundance and body condition of skinks on Stephens Island (Takapourewa). I tested the prediction that only one, Oligosoma infrapunctatum, of the four skink species (Oligosoma lineoocellatum, O. nigriplantare polychroma, O. infrapunctatum andO. zelandicum) will benefit in terms of abundance and distribution from revegetation. Stephens Island is a Wildlife Sanctuary in the north-western Marlborough Sounds, New Zealand. The island is known for its diverse and abundant reptile community. Prior to the mid 19th century Stephens Island was covered in forest. Nearly 80% of this forest was destroyed following the establishment of a lighthouse and farm on the island in 1894. In 1989, when the control of Stephens Island passed to the Department of Conservation, reforestation became a key conservation goal. Stephens Island is currently a mosaic of different habitat types from pasture to coastal forest. Pitfall traps caught skinks for a mark-recapture study in four replicated habitat types: forest, tussock, pasture and replanted.<br><br>Oligosoma lineoocellatum comprised 75% of all individuals caught. Densities of O. lineoocellatum were higher in replanted habitat (3020/ha in December and 3770/ha in March) than tussock (2690/ha in December and 2560/ha in March) and lowest in the pasture (1740/hain December and 1960/ha in March). Rates of captures were too low to perform density estimates for the other three species. Trap occupancy rates indicate O. nigriplantare polychroma is more common in the tussock habitat, and O. infrapunctatum is more common in the replanted habitat. Few O. zelandicum were found, primarily in the tussock habitat. Pasture areas replanted 13 years ago (now scrub habitat) support a higher diversity and abundance of skinks. Forest areas remain depauperate of skinks. Skink preference for replanted areas suggests that, for now, revegetation benefits their populations, possibly due to greater food sources, lower predation pressure and a wider thermal range.<br><br>Body condition (log weight/ log snout-vent length) and proportion of tail loss of skinks were similar in the different habitat types. However, both O. nigriplantare polychroma and O.lineoocellatum had higher body condition in the replanted than the tussock habitat. Juvenile skinks had significantly lower body condition and a lower proportion of tail loss. Skink body condition was not negatively affected by revegetation or by different habitats, despite the large differences between the habitats. Revegetation currently benefits skink populations. Maintaining a mosaic of habitat types is recommended, because, should revegetation create more forest habitat through plantations or plant succession, it is likely that the population of all four species of skink will decline.<br>