Fourteen Northern tuatara of rare Cuvier Island descent, bred at Auckland Zoo, are today being released back to their ancestral home off the Coromandel peninsula.

The Auckland Zoo Conservation Fund is funding the translocation of the three-year-olds, which will boost this Cuvier Island population (estimated to be around 30) by close to 50 per cent, to 44 animals.

Since receiving six adult Cuvier tuatara from the Department of Conservation (DOC) in 1990, the zoo has now bred and released 34 Cuvier-origin tuatara onto the island as part of DOC's 'Headstart' tuatara breeding recovery programme. The first release (seven animals) took place in 2001.

"It's a great feeling to be releasing these youngsters back to their ancestral home after rearing them for the past 37 months. Tuatara are both incredibly slow breeding and slow growing - but now, with all of them over 80 grams, these guys are big enough to defend themselves against natural predators like birds and adult tuatara. There's also plenty of food for them here, and a diverse habitat, so they're in for a good life," says the zoo's NZ Fauna team leader, Andrew Nelson.

A former lighthouse station, Cuvier Island was cleared of the kiore (Pacific rat) by DOC in 1993, and since this time, both reptile and invertebrate populations have exploded. The island, home to saddlebacks, bellbirds and red-fronted kakariki, has also seen the return of five species of seabird.

Hauraki Area Islands DOC ranger, Rob Chappell, says while hard to find on the rugged 196ha island, there is evidence that released tuatara are doing well.

"Last February when the zoo released two juveniles, we came across one of the tuatara we released back in 2003, clearly thriving in Cuvier conditions. Tuatara don't reach sexual maturity until 14 years, and could wait many more years until they decide to breed, so a significant increase in the population is some decades away," says Mr Chappell. "We're on tuatara time here!"

In addition to this release, two eggs from a clutch laid at the Zoo last November, are currently incubating at Wellington's Victoria University. Also a partner in the 'Headstart' programme, the university is carrying out research into the influence of temperature on tuatara sex, and the effects of global warming. Once hatched, the tuatara will relocated back to the zoo for rearing.

"Tuatara are very temperature dependent. On average, eggs incubated at 23 degrees Celsius produce males, and those incubated at 20 degrees Celsius produce females. However, we have found that even a less-than-one-degree difference in temperature can be the deciding factor in producing males or females" says Victoria's School of Biological Sciences senior lecturer and coordinator of the study, Dr Nicola Nelson.

"There have been more warmer than cooler years over the past 35 years, and in the next 100 years it is predicted that New Zealand will become one to two degrees warmer. To ensure tuatara can thrive in the wild, and to avoid skewing populations producing more males - the key will be ensuring tuatara have diverse habitats, so eggs can be laid in environments with a range of temperatures," says Dr Nelson.

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