High-elevation landforms limit the movement of invasive small mammal species

Abstract

Context Large-scale programs for eradication of pest mammals are confronted with the challenge of managing reinvasion. Exploiting high-elevation landscape features that naturally limit the rate of reinvasion is a strategy that is presumed to improve the success of such initiatives, however, the efficacy of doing so has not yet been investigated. Objectives We aimed to assess whether high-elevation landforms limit the movements of 10 species of invasive small mammal in New Zealand to such a degree that they could be exploited in landscape-scale eradication programmes. Methods We determined the upper elevation limits of species’ distributions, and made spatial predictions based on occupancy models. We applied these in concert to a 310,000 ha area of rugged mountainous environments and identified landforms that function as dispersal barriers to each species of interest. We validated our predictions with existing presence/absence and GPS movement data, and tested our predictions of high-elevation landform barriers with the GPS movement data of a sample of European hedgehogs (Erinaceus europaeus). Results We found that the extent of barriers which limited movement ranged from widespread (5/10 species), to localised, (3/10 species) to limited (2/10 species). Our predictions of hedgehog movement barriers were strongly supported by GPS movement data of 26 hedgehogs that were tracked in the study area. Conclusions Our findings show there is enormous potential to advance landscape-scale eradication of invasive small mammals in areas adjacent to high-elevation landforms by identifying and exploiting landscape features that limit the movement of target species in the strategies of eradication programmes.

Eradicating an invasive mammal requires local elimination and reduced reinvasion from an urban source population

“…Large‐scale eradications typically progress across sequential management zones (Anderson et al, 2017; Bell et al, 2019) that are connected to other land areas. Management zones might be contiguous with unmanaged areas, or they may be divided by landscape features that act as barriers to reinvasion (e.g., rivers, high‐elevation land forms, peninsulas) (Anderson, Pepper, et al, 2022; Foster et al, 2022; Innes et al, 2019). The target species' population in areas adjacent to the management zone might be uncontrolled or only partly reduced, forming a source population of reinvaders (Anderson, Pepper, et al, 2022; Hanski, 1998).…”