Females to order

Forest and Bird, Issue 313, 1 August 2004, Page 31

Females to order

ontrolled laboratory incubation has played a major part in the success of the tuatara recovery programme, in particular the ability to influence gender through varying incubation temperatures. The phenomenon of temperature-dependent sex determination has long been known in other reptiles, such as crocodiles and turtles; now research undertaken at Victoria University has confirmed that incubation temperatures also influence tuatara gender. "We have been able to establish that warmer temperatures produce males in tuatara populations, Dr Nicky Nelson explains. ‘The implications are that we need to incubate at multiple temperatures to ensure some of each sex. On Little Barrier, for example, the warmer temperatures naturally produce more males but we would ideally like two females to one male, because males have annual breeding cycles and females breed every two years. "We visited the island in 2002 and sexed the young captive tuatara by laparoscopy to determine male/female ratios. In the laboratory incubator we are able to keep temperatures constant, and we know that from 21° up produces males and below 21° produces females. Hence we can incubate eggs to produce males or females to order. Nicky Nelson completed a PhD funded by the Marsden Fund studying tuatara incubation in captivity, and is now completing post-doctoral study on the effects of global warming on tuatara populations. Her study is being sponsored by the Zoological Society of San Diego.