Zealand Lizards Research Articles

Natural history of the lizards of the three kings Islands, New Zealand

The herpetofauna of the Three Kings Islands comprises one gecko (Hoplodactylus aff. H. pacificus) and four skinks (Cyclodina ornata, Oligosoma fallai, O. smithi, and O. suteri). Great, North East, and South West Islands have all five species, and the other islands and islets each have 2–4 species. Hoplodactylus aff. H. pacificus and O. suteri have the widest distribution (10 islands each) followed by O. fallai on nine islands. The lizard fauna is relatively depauperate, probably because of the islands’ degree and length of isolation. O. fallai, endemic to the Three Kings group, is mostly diurnal but also active at night. Specimens of Hoplodactylus aff. H. pacificus collected from the Three Kings Islands were significantly larger on average (82.1 mm) than specimens of H. pacificus from elsewhere (69.1 mm) and may constitute an endemic subspecies or species. Specimens of O. suteri had a maximum snout‐vent length of 126 mm on the Three Kings group, compared with 108 mm elsewhere. There was no sexual dimorphism in snout‐vent length in Hoplodactylus aff. H. pacificus, O. fallai, and O. suteri. Specimens of O. fallai from forest were significantly larger on average than those from scrub, which were in turn larger than those from coastal sites. In both Hoplodactylus aff. H. pacificus and O. fallai there was evidence that not all mature females bred every year, consistent with a trend towards low annual reproductive rates among New Zealand lizards.

Microsatellite DNA markers for New Zealand skinks

Reptiles are a prominent part of the faunal diversity of New Zealand, but most species have suffered major range declines or extinctions in the past 2000 years. Nearly fifty percent of species (26 of 62) are now threatened or restricted to offshore islands and eight are subject to recovery programs (Towns and Daugherty 1994; Towns et al. 2001). Most declines can be attributed to loss or modification of habitat and predation by introduced mammals. Previous genetic studies of New Zealand reptiles have increased the number of recognised species (e.g. Daugherty et al. 1990), but provided little autecological or population-level genetic information that could be applied to management. Here we present the first microsatellite DNA markers to be developed for a New Zealand lizard. We are using these markers to study dispersal in the grand skink, Oligosoma grande, a large rock-dwelling lizard endemic to sub-alpine grasslands in southern New Zealand. This formerly widespread species now has a restricted range, and is listed as ‘vulnerable’ under IUCN criteria (HiltonTaylor 2000).

Conservation of New Zealand lizards (Lacertilia: Scincidae) by translocation of small populations

The successful removal of rodents from islands around New Zealand has enabled translocation of rare species of lizards to new sites within their former range. Four species of skinks were translocated to Korapuki Island, Mercury Islands, New Zealand: Cyclodina alani, C. oliveri, C. whitakeri and Oligosoma suteri. Responses of three of the lizard species to release were predicted using a deterministic population model then compared with the actual performance of wild populations. The population models predicted that if populations of about 30 C. whitakeri and O. suteri were released, C. whitakeri would be increasing by 7% p.a. and O. suteri would be increasing by over 35% p.a. during year five. If 20 C. alani were released, the population could be increasing by 70% p.a. during year five. Population expansions are being recorded for all three species, but observed population increases were lower than those predicted for two species, partly because of low catchability of immature lizards. The lowest rate of increase (up to 7% p.a.) was for C. whitakeri. Low rates of population expansion found in species such as C. whitakeri raise a conundrum: the rarer a species is, and the lower its annual reproductive output, the larger the number of individuals that may be required for translocations to succeed. Translocations may be regarded as successful when new populations are self-sustaining and comprised only of locally born animals. Despite the populations increasing, it may not be possible to claim success for the three intensively studied species on Korapuki Island until at least 20 years after release. This is because of longevity of the founders, which are still being caught up to 12 years after release. Extreme longevity, and hence prolonged post-release monitoring, is likely to be a recurrent problem for translocations of rare lizards.

Haemoparasitic protozoans (Plasmodiidae and Haemogregarinidae) from a New Caledonian gekkonid lizard, Rhacodactylus leachianus

A Plasmodium sp. and a haemogregarine were found in Giemsa-stained blood smears of a Rhacodactylus leachianus, an endemic New Caledonian gekkonid lizard. Both parasites were observed in mature erythrocytes only. The haemogregarines were found in a lateral position and the stages of Plasmodium sp. were polar or lateropolar in the cells. Mature schizonts of the latter were often fan-shaped, producing 4–10 merozoites. This is the first record of blood parasites in a New Caledonian vertebrate and the first record of a Plasmodium from a carphodactyline gecko. The Plasmodium sp. is unlike those described from Australian or New Zealand lizards, but is referable to the subgenus Lacertamoeba. The biogeographic affinities of these parasites remain unclear and may reflect either ancient Gondwanan affinities or more recent southeast Asian connections via more highly vagile lizard invaders of New Caledonia.

The role of ecological restoration in the conservation of Whitaker's skink (Cyclodina whitakeri),a rare New Zealand lizard (Lacertilia: Scincidae)

Abstract A programme to improve the conservation status of Whitaker's skink (Cyclodina whitakeri), previously confined to <20 ha of usable habitat, is described. The programme involved eradication of introduced Pacific rats orkiore (Rattus exulans) from 18 ha Korapuki Island (Mercury Islands, north‐eastern New Zealand), documentation of the response of five species of resident lizards to release from the effects of rats, and transfer of 28 Whitaker's skinks from nearby Middle Island between 1988 and 1990. Following removal of rats from Korapuki, resident lizard numbers at some coastal sites increased within 12 months and rose 30‐fold over 5 years, but measurable increases of numbers of lizards in forest areas took up to 6 years. Fifteen of the founding Whitaker's skinks on Korapuki Island have been recaptured 36 times since their release, and five Korapuki‐born young have also been caught. The population is now estimated as 33. The increase in number of resident lizards and the success of the introduction of Whitaker's skinks demonstrate that predation rather than habitat deficiencies were responsible for the depleted resident lizard fauna on Korapuki Island. Repatriation strategies for species with low intrinsic rates of increase are proposed.

The effect of temperature on the metabolism of juvenile tuatara,Sphenodon punctatus

Abstract Resting metabolic rates of juvenile tuatara (1–2 year old) were found to be significantly affected by ambient temperature over the range 5–22.5°C. The younger, smaller animals had higher rates of mass‐specific metabolism than the older and larger juveniles, significantly so at the lower and higher experimental temperatures. There is evidence of a compensatory, temperature‐independent metabolic decline in juvenile tuatara in the mid‐temperature range, similar to that found in other cool‐temperate reptiles. The mass‐specific metabolic rates of juvenile tuatara are high when compared with a small data sample of metabolic rates for adult tuatara, but similar to those of some small New Zealand lizards.

The reproductive cycle of the male tuatara, Sphenodon punctatus, on Stephens Island, New Zealand

Abstract The reproductive cycle of male Sphenodon punctatus is characterised by continuous sexual activity. Spermatocytogenesis is uninterrupted, though abnormal in some cells, and probably very slow in winter. Spermiogenesis is normal from mid spring to mid summer, then becomes abortive and finally ceases during the 5 or 6 coolest months. The epididymal duct, which is hypertrophied during the mating period in summer, remains partly developed during the rest of the year. The kidney has no sexual segment. Many spermatozoa are present throughout the year in the deferent ducts of males, but their number gradually decreases in winter and at the beginning of spring. The reproductive cycle of the male tuatara is similar, but not identical, to that of the few New Zealand lizards that have been studied, but differs markedly from all types of cycles, known in reptiles, from other parts of the world.