Reproduction and life history of New Zealand lizards

Abstract

New Zealand lizard species are characterised by their high incidence of viviparity (99% of taxa) and ‘slow’ life histories. Female geckos and skinks typically mate and begin vitellogenesis in autumn, store sperm over winter and ovulate in spring. Pregnancies usually last at least 3 months, but gestation length, which is temperature dependent, may reach 14 months in some geckos (especially nocturnally foraging species). Some female geckos and skinks reproduce less than annually. Male geckos and skinks exhibit spermiogenesis during summer and/or autumn, with prolonged or continuous spermatocytogenesis and no period of complete testicular regression. Several features (autumn mating with prolonged vitellogenesis, possibility of a secondary mating season in spring, prolonged pregnancies with sometimes less-than-annual reproduction in females) have parallels with Tasmanian and South American lizards from similarly cool climates. Parallels also exist with New Zealand’s egg-laying tuatara (Sphenodon punctatus), including less-than-annual reproduction, prolonged embryonic development and continuous spermatocytogenesis. Compared with sympatric skinks, geckos from temperate zones in New Zealand appear distinctive in their ability to retain fully developed offspring in utero over winter, to begin vitellogenesis before pregnancy has ended and to maintain a stable size of the testes and abdominal fat bodies year-round. New Zealand lizards generally exhibit traits at the slow end of the life-history continuum for small-bodied lizards. In particular, New Zealand geckos are exceptionally long-lived (at least 3-5 decades in the wild in several species), and, with clutch sizes ≤2, have extremely low annual reproductive output. Some ideas for future research are presented.