‘Calling all wetas…calling all wetas’
By GEOFF MERCER
Scientists bug rare bugs
Ten Cook Strait giant wetas on Maria Island have trudged about for two weeks wearing tiny backpack transmitters.
The transmitters sent signals back to a hand-held receiver which Victoria University scientist Mary McIntyre used to track them each night. She then calculated how far they ranged.
“The tricky bit is not standing on them when you get close,” she said.
Dr McIntyre is counting them so that when new species are introduced to the island, their effect on the weta population can be assessed.
Conservation Department staff are considering releasing tuatara and birds such as takahe on the island. The takahe and tuatara eat wetas.
Dr McIntyre’s tracking efforts confirmed wetas range up to 50 metres a night. But she said more studies of wetas’ wandering habits were needed before Mana Island’s population could be estimated.
Department of Scientific and Industrial Research staff built the transmitters at a cost of $220 each. They were stuck to the wetas with harmless silicon gel. This is only the third time in the world that transmitters have been attached to insects. They have been used on what is thought to be the world’s largest insect, the Amazon Goliath beetle, and solar powered transmitters have been mounted to South American killer bees to chart their progress towards the United States.
Dr McIntyre said wetas, being active at night, did not suit solar powered transmitters and had to carry their own battery.
Tracking them with transmitters had been approved by the Conservation Department’s ethics committee.
She said Mana Island’s weta population had increased now that mice had been eradicated from the island.
Cook Strait giant wetas were formerly widespread from Wanganui to Wellington, and perhaps as far as Kaikoura, but were now limited to rat-free islands. There were nine weta species, all unique to New Zealand. The wetas survived on Mana Island, Stephens Island in the Marlborough Sounds, and in an artificial population on Maud Island.
Photo caption – A weta wearing a back pack transmitter with its own aerial negotiates a tahinu (cassinia) flower on Mana island.