Feral pigs (Sus scrofa) were introduced to Auckland Island in subantarctic New Zealand in 1807. They established and became invasive, subsequently causing substantial unwanted impacts on native biodiversity. Understanding pig movement behaviour and habitat selection can lead to focused, efficient, and effective management efforts, especially during initial knockdown of the population. Here we used location data from ARGOS telemetry collars deployed on 15 Auckland Island pigs from 2007 to 2008 to estimate seasonal homerange sizes and habitat selection. The annual home-range sizes of pigs ranged from 1.26 to 36.4 km 2 , with a mean of 14.1 km 2 (SD = 11.3 km 2 ). The variation in home-range sizes between winter and summer was generally low. We found that the pig population selected areas of their home ranges that were on average closer to the coast (though this was not necessarily selection for beaches or strandlines per se) during the spring and summer months. Pigs also selected areas closer to the coast in winter, albeit with weaker strength of selection than in spring and summer. We had insufficient data to differentiate between different coastal habitats (i.e. cliffs versus beaches and strandlines). We also found that pigs showed annual selection for tussock, hills with north-facing aspects, and rivers and streams. They avoided areas of bog-swamp and forest-scrub. Importantly, we do not know what food resources or other factors were driving habitat selection. Our results highlight areas selected by pigs that could be targeted for initial knockdown; however, staff will have to search all habitats on the island to achieve rapid eradication or a protracted mop-up of survivors. Simply targeting key accessible areas like strandlines and coastal forests will not achieve eradication. Based on these home-range sizes, eradication would require a hunter path spacing of no more than 1.4 km to ensure every pig home range was searched at least once.
Context. Bennett's wallaby (Notamacropus rufogriseus) was introduced into New Zealand in the late-1800s, and has subsequently become a significant pest to agriculture, silviculture, and native vegetation. Effective management of wallabies requires robust spatial and temporal ecological information, which can be used operationally to increase detection and kill rates. Aims. To determine home range size and shape, resource (i.e. habitat and topography) selection, and daily movement patterns of three populations of Bennett's wallaby in the South Island. Methods. We attached GPS-collars to 38 adult wallabies (17 females, 21 males) between May 2018 and May 2019, and obtained usable location data from 30 individuals. We used kernel density estimators and resource selection functions to quantify seasonal home ranges and resource selection, respectively. Key results. The mean seasonal home range sizes of males and females were similar (26.8 ha and 24.8 ha, respectively; combined range = 1.2-101.9 ha), although the largest home ranges belonged to large males. Resource selection was strongly influenced by distance to concealment cover, ridgelines and streams, i.e. wallabies selected to be closer to these features, though not necessarily at them. Wallabies selected areas close to concealment cover throughout 24-h periods, but most strongly during the day, which is when they bed in dense cover. Wallabies sampled outside of peak breeding moved most during dusk and dawn (median = ~50 m/h), whereas those sampled during peak breeding moved widely during day, dusk, and night (110-280 m/h), but not dawn (median = ~50 m/h). Conclusions. The home range sizes of wallabies in New Zealand were highly variable, but on average were similar for males and females. Wallabies selected pasture close to areas with some cover, suggesting a trade-off between access to high-quality forage and concealment cover. Implications. Our results provide robust data for modelling management strategies for wallabies, and contribute directly to operational planning by identifying habitats where wallabies are most likely to be found temporally. This information can be used to determine the appropriate survey methods and control tools to maximise detection rates and kill rates of wallabies, based on habitat.
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