Staff at a Northland conservation park fear for the lives of seven geckos stolen from their locked enclosure overnight.

The native forest geckos, four female and three male, were snatched from their enclosure at Whangarei Museum and Heritage Park between 8pm last night and 9.15am today, park director Sue Walters said.

The geckos were a threatened species and required special care, she said.

"The staff are absolutely gutted, and really concerned for the geckos' welfare," she said.

"We're appealing to the thieves or anybody who knows anything to return them, they need special care and if they don't get it they could die, or they certainly could suffer."

Ms Walters said the lizards required special food, could easily drown in a large water bowl and could grow potentially fatal mould in the wrong environment.

"We're just really anxious to get them back," she said.

Four geckos, two green and two forest, were stolen from the park in July 2006.

One special lizard, named Fat Albert, escaped the thieves four years ago but was taken in last night's raid.

Fat Albert was known for eating all the flies before the other lizards could get to them.

Security was increased after the 2006 theft, including the installation of a 1.82m high fence.

Ms Walters said was not sure why people would take the geckos but there was documented evidence of them being stolen for sale on the black market or to be kept as pets.

Police are investigating.