Oregus inaequalis Castelnau, its distribution, and abundance at Swampy Summit, Otago

Abstract

A comprehensive study was undertaken to determine the historical and current distributions of Oregus inaequalis, its abundance at Swampy Summit and the possibility of hedgehogs as potential predators. The report details six key characteristics that allow field distinction of Oregus inaequalis from coastal Otago Oregus aereus s.l. Extensive pitfall trapping indicated little range contraction based on the known historical distribution, but there was no recorded extension of the known range. O. inaequalis was recorded at Swampy Summit, Leith Saddle, Mt Cargill, Leith Valley (three sites) and Ross Creek Reservoir (both upper and lower portions of the reserve). No sound estimate was obtainable of the abundance of O. inaequalis at Swampy Summit. However, the population appears to be considerable and is unlikely to be declining. Trapping indicated that the period of greatest beetle activity was November-December, which represents the most suitable time for any future monitoring. Hedgehogs could not be excluded as predators of O. inaequalis, but further sampling is required before a conclusive statement can be made. No further monitoring is recommended at Swampy Summit, but a resurvey of Mihiwaka is recommended to confirm the absence of O. inaequalis from a location where it was previously recorded. Monitoring is recommended for all sites if they are subject to major disturbance (e.g. fire) to determine the resilience of known populations. Development on remaining native forest refugia in the Leith Valley should be discouraged, as it is likely that this represents the original habitat type for O. inaequalis.