Tuatara (Sphenodon) in captivity

Abstract

Prior to about 1990, tuatara (Sphenodon) did not generally survive well in captivity. Wild populations have been restricted to the offshore islands of New Zealand since before the arrival of Europeans, protected by law from open access since 1895, so the only tuatara that could be seen by the general public have been in captivity. My study encompasses aspects of biology, physiology, taxonomy, distribution, past and present husbandry, the incubation experiments and management of the hatchlings resulting from artificial incubation, juvenile and adult mortality and health and management of the captive population covering the period from the late 1870s to 2001. Two groups of juvenile Sphenodon punctatus and S. guntheri hatched artificially at Victoria University of Wellington formed my study groups for research into juvenile survival and mortality. I have reviewed the literature, government records and the records provided by tuatara holders before 1996 in order to investigate why captive tuatara have not done well, how the available knowledge has been applied to captive management, and the effects of the resulting practices. Records before 1990 were sufficient to confirm poor survival of tuatara in captivity. Most information from the nineteenth century focussed on tuatara anatomy and taxonomy, followed by research on isolated aspects of physiology which could not be applied directly to the survival of tuatara without interpretation. Failure of environmental control systems, particularly outside New Zealand, keeping tuatara too warm, not allowing for seasonal fluctuations in photoperiod and temperature, feeding them too much and too often with food that probably has not been nutritionally complete, and not recognising and treating illness adequately have contributed to poor tuatara survival. Since 1990 survival of adult and juvenile tuatara has increased, with the improvement in husbandry which has followed the involvement of Victoria University of Wellington (VUW) and the increasing experience of a wider range of holders than previously. Tuatara do not yet breed readily in captivity, apart from the pairs (Auckland Zoo, Southland Museum and Art Gallery) and one group (National Kiwi Centre, Otorohanga) that have produced young regularly since the early 1980s. Larger groups with more than one male are being formed to accommodate the social interactions believed to be necessary for successful breeding. The only new breeders since 1990 were Sphenodon punctatus at VUW, and Peacock Springs in Christchurch, Sphenodon p. punctatus from relict northern island populations held in groups at Auckland Zoo temporarily and the Little Barrier Island tuatara held in situ. Whereas the Red Mercury Island group produced enough youngsters to safeguard the population and have been translocated onto the island with their juveniles, the Cuvier Island and Stanley Island groups have yet to do so. Investigating perinatal husbandry practices with juvenile tuatara showed there was no significant difference when comparing survival of juveniles above or below of the mean weight at hatching, of moving them from the natal area either side of the mean age at transfer, or of moving them from the natal area in any season of the year. Survival increased significantly when juveniles were first transferred when they weighed more than ten grams. Radiography of gravid females did not affect the first generation when comparing the number of abnormalities in eggs or hatchlings with those from females that were not X-rayed. Deaths in juvenile tuatara of both species in the study group declined once they were approximately four years old. While the Tuatara Recovery Plan (Cree & Butler, 1993) was successful in preventing further extinctions of wild populations, it is only with the revised Tuatara Recovery Plan 2001-2011 (Gaze, 2001) that the captive population of Stephens Island tuatara has been given status in its own right. It is to be retained in captivity, managed to self-sustainability and used to assist advocacy and research. There is still insufficient information on tuatara nutrition, light requirements, health and some aspects of reproduction to meet the objectives of the recovery plan.