Abstract
Wētā, large wingless anostostomatid orthopterans, have been the most frequently translocated insects in New Zealand. Until recently, such translocations were only monitored intermittently to confirm presence. We investigate the spread of Cook Strait giant wētā (Deinacridarugosa Buller, 1871) after its release on Matiu/Somes Island, Wellington, New Zealand, in 1996. Adult wētā were surveyed from 2008 to 2016 using footprint tracking tunnels and/or searching with spotlights at night. The population underwent a reversal in distributional abundance after 2008. In 2008, they were abundant in the north and rare in the south but by 2013 and 2015 they were relatively less abundant in the north and common in the south. Why they diminished in the north remains unknown but possible causes are predation on juvenile wētā by nocturnal geckos (detected in the north and east but not in the south), by some habitat change (mostly reduction of some lawn), or by a combination of these together with removal of wētā from the north for translocation elsewhere. Further research is required to confirm which of these factors affect wētā abundance, if there are other causes, and if any further change in distributional abundance occurs.
Highlights
Translocation, the deliberate movement of living organisms from one area to another (IUCN/SCC 2013), is an important tool in conservation management and restoration
We investigate the spread of the Cook Strait giant wētā, Deinacrida rugosa Buller, 1871, after 62 individuals were released on Matiu/Somes Island, Wellington, New Zealand, in 1996 (Gascoigne 1996; Fig. 1)
All analyses were conducted in Genstat 18 (VSN International 2014). Changes in both distribution and abundance.—In both 2013 and 2015, adult D. rugosa were most frequently found along the paths and on mowed lawn at the southern end of the island (Southwest transect).The lowest numbers were found in the north (North transect) and along the eastern side of the island (Northeast and Southeast transects)
Summary
Translocation, the deliberate movement of living organisms from one area to another (IUCN/SCC 2013), is an important tool in conservation management and restoration. Seddon et al (2005) reported that 9% of 699 species of plant and animal reintroductions involved invertebrates. This is despite invertebrates being ideal candidates for translocations because of their small size, high reproductive output, and small spatial requirements (Pearce-Kelly et al 1998). Conservation interventions applied to ensure long-term persistence of giant wētā most frequently involved translocations to islands or to fenced sanctuaries on the mainland where mammals had been eradicated or kept at low densities (Watts et al 2008a). Giant wētā and tree wētā (genus Hemideina) were the most frequently (71%) translocated insects in New Zealand and until recently, such translocations have only been monitored by intermittent surveys to confirm presence (Sherley et al 2010)
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