Seven protected geckos stolen from a Northland conservation park could be worth thousands of dollars to someone selling them on the international black market.

Staff at the Whangarei Museum and Heritage Trust were yesterday devastated to learn that the reptiles - including one named Fat Albert which was the only survivor of a gecko burglary at the park four years ago - had been stolen overnight.

Park director Sue Walters said the thieves scaled a fence around the perimeter of the park, another fence inside and jemmied a steel padlock on the gecko enclosure.

The raid happened some time between 8pm on Monday when a security guard checked the park and 9am yesterday when Kiwi House co-ordinator Kevin Saxton opened up. Police were called and are investigating.

Ms Walters said the biggest worry was that the animals would not be fed properly and would die of starvation.

"It's quite hard on the staff that cared for them, their keepers. One gecko was a little unwell last year so he was carefully nursed back to health."

The geckos, four female and three male, were all of mature age.

Six had been bought from parks around the country after four geckos were stolen in 2006.

Despite a Customs alert, the original geckos were never found.

Since the first incident, the park had beefed up security, including installation of a 1.82m fence, Ms Walters said.

Stuart Williamson of the Wildlife Enforcement Group - which comprises Customs, the Department of Conservation and the Ministry of Agriculture and Forestry - said the geckos could be worth about $2000 in Europe.

"We are aware of some in trade overseas, so they might be smuggled out at some time. It's difficult to say exactly how much they are worth at any one time as it is based on demand."

Mr Williamson said it was an offence under the Wildlife Act to take the native geckos out of the country.

Offenders could face a $100,000 fine - with an added $5000 per animal - and/or imprisonment of up to six months.

There are also cases in New Zealand of lizards stolen to be kept as pets.

In March, a Swiss stockbroker and a chef from Mexico were jailed for 18 weeks after taking protected jewelled geckos from the Otago Peninsula.

They were arrested after a German man, Manfred Walter Bachmann, was found in Christchurch with 16 geckos in tubes in his backpack. He was sentenced to 15 weeks in prison.

In January a German man who tried to smuggle 44 live geckos and skinks out of the country in his underwear was sentenced to 12 weeks in jail.

Hans Kurt Kubus, 58, was caught trying to board a flight at Christchurch Airport with the animals.

Anyone with information should call Whangarei police on (09) 430-4500.