Common skinks, Leiolopisma nigriplantare rnaccanni, are the most numerous and widespread skinks in New Zealand. The aim of this study was to examine the ecology of the subspecies in tussock grasslands in Otago, where it occurs in particularly large densities. The study was concentrated on an area on the Rock and Pillar and Lammermoor ranges. Three morphs of L. n. maccanni were present in this area. These were distinguishable by physical characters colour patterns, body ratios and scale counts, as well as developmental characters such as size at sexual maturity and the number and size of offspring produced. On the basis of these characters and electrophoretic analysis of protein differences, the hypothesis is raised that the three morphs are three reproductively isolated species, designated L. maccanni and Leiolopisma spp. 1 and 2. These species appear to be numerous and widespread in the South Island and on various islands off the coast of the South Island. Other species may also be presently classified as “L. n. maccanni". The hypothesis that L. n. maccanni is a species complex has significant implications for New Zealand herpetology, which are discussed. Most importantly, it suggests that the New Zealand skinks are a much more ancient group than was previously believed.
Home ranges and territorial behaviour, population densities, habitat preference, niche overlap and competition and the feeding ecology of the three species were studied in the Rock and Pillar-Lammermoor area and in other tussock grassland areas. Differences among the three species occurred with respect to home range size, territorial behaviour, population densities, habitat preference and the size and taxa of prey eaten. The role of these differences in allowing the three species to occur sympatrically in the Rock and Pillar-Lammermoor area was investigated. Different habitat utilization by each species was probably the most important factor in maintaining sympatry in this area. L. maccanni preferred rock outcrops, while Leiolopisma sp. 1 preferred grasses, and Leiolopisma sp. 2 was usually found in herbs and shrubs.
Each species ate a large number of invertebrate taxa, as well as some plant material. The significance of the skinks as invertebrate predators in the Rock and Pillar-Lammermoor area was determined. They appeared to have little influence on invertebrate population densities.
