The female reproductive cycle of a viviparous skink, Oligosoma maccanni, in a subalpine environment

Abstract

The majority of New Zealand's endemic reptiles that have been studied with respect to patterns of reproduction show low rates of annual reproductive output, with extended gestation and great longevity. A well-studied example of extended gestation is the common gecko (Hoplodactylus maculatus) at the subalpine site of Macraes Flat. At this location, females have biennial reproduction with a gestation of up to 14 months, while at a warmer site gestation only lasts 3-5 months. The main aim of this thesis was to investigate whether McCann's skink (Oligosoma maccanni) also has extended gestation at the same subalpine site. Relative clutch mass (RCM) was compared between the two species to investigate possible differences of maternal investment in reproduction. Palpation was used to assess reproductive condition of 0. maccanni non-invasively, and a subset of the sample was dissected to confirm reproductive condition and to test the accuracy of palpation. Both species have autumn-spring vitellogenesis; however, in contrast to H. maculatus, female 0. maccanni are annual breeders with a spring-summer gestation of 4-5 months. I hypothesised that RCM would be smaller in 0. maccanni in comparison to H. maculatus as a trade-off to allow annual reproduction. However, a lack of overlap in body size constrained comparisons of RCM between the two species. I suggest that if an overlap did occur it is unlikely that 0. maccanni have a smaller RCM, and the difference in reproductive cycles is more likely due to other factors. Palpation was accurate in distinguishing vitellogenic, early- to mid-pregnant and latepregnant females from each other. It was also highly accurate in estimating clutch size in females in early-mid pregnancy, but not as accurate in vitellogenic or late-pregnant females. This study has provided important information for evolution and life history studies and for the conservation of 0. maccanni and other New Zealand lizards.