DOC trials release of rare knobbled weevils raised in captivity

Rare Canterbury knobbled weevils bred in captivity have been released into the Ōtūwharekai/ Ashburton lakes area in a trial to see how they cope.

The Department of Conservation (DOC) calls the beetle one of New Zealand’s rarest. It was thought to be extinct until a small population was found at Burkes Pass in 2004. The captive group began with six weevils and now has more than 200.

“The release has gone really well, it’s amazing seeing them scuttle down into the depths of the spear grass to find a new home,” said Tara Murray, DOC Senior Science Advisor.

DOC scientists planned the captive rearing with Te Rūnanga o Arowhenua after another small pocket of weevils was found in Mid-Canterbury late in 2024. Murray says the team worked with a weevil specialist at the Bioeconomy Science Institute at Invermay, and the weevils proved easier to breed than expected.

The release site has Aciphylla plants (taramea/spear grasses), which knobbled weevils favour. DOC says one reason for the species’ decline is the removal of spear grasses, which costs the weevils their habitat.

What happens next

This is a soft release. The plants start with protective covers, which DOC plans to remove in a week or so while it monitors the weevils.

If the trial goes well, DOC and Te Rūnanga o Arowhenua will develop plans to collect more wild weevils for a full-scale attempt to set up new populations. DOC says this would stop the beetles all being in one place, where fires or other natural hazards could wipe them out.

Monitoring at Burkes Pass will continue. Any weevils found there can be brought into the captive rearing facility to help build up the small population.