Are Alpine Wētā Safe from Introduced Predators? A Case Study on the Southern Alps Giant Wētā Deinacrida pluvialis

The Southern Alps giant wētā Deinacrida pluvialis Gibbs, 1999 is a large, ground‐dwelling wētā that inhabits the low‐to‐mid alpine regions about and west of the Main Divide of the Southern Alps, between Milford Sound and the Taramakau River. When the species was first discovered in the 1990s, surveys in the Matukituki River West Branch (Mt Aspiring National Park) and in Price Basin (Whitcombe River, Westland) indicated that the wētā was locally abundant. D. pluvialis was considered safe because it lived at elevations that were thought to be too high for rats. Following searches in 2021 that showed D. pluvialis had most likely gone extinct in the Matukituki Valley, in 2022 the species was reclassified from “Not Threatened” to “Threatened, Nationally Endangered” in the New Zealand Threat Classification System (NZTCS). Here, I present the results of the 2021 surveys in the Matukituki Valley, and of 2026 surveys in Price Basin, and in the Neale Burn (Milford Sound, Fiordland). The latter location was searched following a sighting of D. pluvialis 3 years prior. The giant wētā encounter rate in Price Basin dropped by more than 90% between 1992 and 2026. In the Neale Burn, no wētā were found, and tracking tunnel lines at 1200 m a.s.l. yielded a visitation rate for rats ( Rattus sp.) up to 30%. The results of all surveys show a consistent, strong decline of D. pluvialis throughout its geographic range. Circumstantial evidence points to mammalian predation being the main cause for the observed decline. Survey methods used and their limitations are also discussed.