They wrestle with their tusks — and they are coming back from the brink

The Mercury Island tusked wētā is a heavy, flightless insect with an unlikely party trick: rival males wrestle, tusks locked, each trying to flip the other. In the 1990s, introduced rats had driven it to perhaps 120 individuals on a single small island off New Zealand's Coromandel Peninsula. Conservationists collected just three to start a captive breeding programme, then released their offspring onto predator-free islands. Ecologist Simon Lamb, visiting Ohinau Island to monitor seabirds, kept noticing wētā far from where they were released — and realised the insects had spread across the island on their own. Populations that took nine years to creep 180 metres on one island are now expanding by up to 100 metres a year. Slow, stubborn, unmistakable: a comeback measured in metres, won in decades.

SDG 15 · Life on land — Mechanism: institutional program