Massive Wētāpunga Recovery Sees Species Shift From Endangered To Increasing

The world's heaviest insect has pulled off a stunning recovery after conservationists saved the giant bug from going extinct. An adult female wētāpunga can weigh as much as a mouse, grow nearly four inches long, and boast a leg span stretching eight inches wide. These massive creatures once roamed across New Zealand's North Island before predators and habitat destruction pushed them to the edge. Now, their numbers in the wild are finally climbing thanks to an industrialized breeding effort.

Over the last 15 years, scientists bred and released 11,000 wētāpunga at 10 carefully selected sites around New Zealand. Monitoring on two protected islands shows these bugs have built self-sustaining populations now in their fourth generation. Thanks to this work, the species' status shifted from 'nationally endangered' to 'nationally increasing'. Dr Chris Green, an honorary researcher at the Department of Conservation who tracked the release programme for a new study, stated: 'The future of wētāpunga is looking bright.'

These nocturnal plant-eaters are among New Zealand's unique species that suffered dramatic losses in the last century. Cats, rats, and stoats entered otherwise predator-free areas, sending wētāpunga numbers tumbling as their native habitats shrank. By the 1990s, officials declared them endangered; they were presumed extinct on the mainland. Their entire remaining population huddled on a single island in the Hauraki Gulf with only a few breeding adults left.

After ratters successfully cleared rats from that island, populations began to slowly recover, rising from just 78 in 2005 to 172 in 2009. Yet conservationists worried this pace was not enough. Starting in 2008, researchers collected six breeding-age wētāpunga from the wild and brought them back to Butterfly Creek, a wildlife facility, and Auckland Zoo. Slowly, they bred the first generations of wētāpunga raised outside the wild or ex situ.

As techniques improved and the ex situ population grew, researchers ramped up production, eventually rearing tens of thousands of baby wētāpunga. Young insects known as nymphs live in communal creches until they are large enough to move to individual adult cages for breeding or release. During this time, they eat a specially designed three-part diet of fresh greens, leaf litter and fish flakes for protein. Adding extra protein is critical for young nymphs' survival – just one trick conservationists learned while developing their massive breeding programme.

There have now been 45 separate releases of wētāpunga into the wild on eight predator-free islands and two fenced-off nature reserves across north Auckland. Intensive population monitoring shows efforts are starting to pay off. On Motuora and Tiritiri Matangi islands, at least four generations of wētāpunga have been born. This confirms the giant species successfully established populations on both islands. Likewise, researchers confirmed many other island populations are also nearing this milestone.

Researchers now hope techniques developed for saving this massive insect could protect New Zealand's other threatened animals. The success was published in the New Zealand Journal of Zoology. Dr Green noted: 'There are many more critically endangered invertebrates that could benefit from similar programmes, for example the Canterbury knobbled weevil, and several native stag beetle species.