We've nicknamed the Mt Arthur giant wētā, Deinacrida tibiospina, 'Tibio', after its species name. FOF volunteers led by Lesley and Martin have monitored the Tibio population on the Wharepapa ridge since 2016, using minimally-invasive, unbaited, tracking tunnels. Tibio are nocturnal and after much night-searching we coaxed a wētā to walk over an inked card and discovered that they leave distinctive prints. The proportion of cards tracked by wētā provides an index of abundance. We've seen the index fall after mouse irruptions. Tibio is more vulnerable to predation than most wētā because it lives on the ground in tussock grassland rather than in a defendable 'house' such as a tree cavity. Despite this, it has been a low priority for conservation action because rodent numbers and hence predation risk were thought to be low in the alpine zone.
FOF's monitoring has shown that this is no longer the case. In 2022, Tibio was classified as critically threatened. This means that without conservation action it will become extinct. Being an alpine specialist, Tibio cannot be given sanctuary on an offshore island or in a fenced enclosure. Continued survival of this, the cutest of the giants, is dependent on Aotearoa developing a mouse control tool that is effective in the massive landscapes of Kahurangi. There is currently no such tool. Like all the giant wētā, Tibio are wingless, so if they are lost from one maunga, re-colonisation will be very, very slow. This makes them particularly vulnerable to climate change.
Thanks to the mahi of FOF volunteers, the threats mice and climate change pose to this charismatic giant wētā are beginning to be understood. FOF's work demonstrates that local, dedicated groups of volunteers can make a difference for invertebrate conservation, even in the harsh alpine environment.
Listen to Jesse Mulligan and Nicola Toki discussing FOF's work with Tibio: Critter of the Week