Late stage deferral of parturition in the viviparous lizard Niveoscincus ocellatus (Gray 1845):: implications for offspring quality and survival

The ability of viviparous lizards to defer parturition after completion of embryonic development is a potentially key strategy for enhancing offspring fitness. Using the spotted snow skink, Niveoscincus ocellatus, we investigated the ability of females to defer birth if placed into cold conditions at the same time, for 1, 2 or 3 weeks at the end of gestation. The ability to defer birth was compared between two populations at each end of the species' altitudinal range. We hypothesized that females from the high elevation population would be less likely to defer parturition under extended periods of poor conditions, thus ensuring that young were not born too late in the season. In all but the 3-week treatment group from the high elevation population, females were able to defer birth when placed under cold conditions: for all groups, there was no treatment effect on offspring phenotype at birth, dispersal distance or survivorship after release. However, there was a significant negative effect of treatment on offspring growth measured after release, with the results differing between the populations. Females from the high elevation population were less able to defer birth under long periods (3 weeks) of cold conditions, and this was accompanied by a decrease in viability of the offspring. (c) 2007 The Linnean Society of London.