Everybody needs good neighbours: movement, habitat use, and conspecific association in a reintroduced mesopredator

Abstract

As a reintroduction progresses through the establishment, growth, and regulation phases, density-dependent mechanisms increasingly drive population dynamics. This can complicate efforts to reinforce these populations if the translocated individuals (henceforth reinforcers) are excluded, or existing residents become displaced. This is especially pertinent for islands and fenced havens, where immigration is often only possible by translocation. Conspecific associations offer insights into how these density-dependent mechanisms manifest in space and time. We investigated how movement, habitat use, and conspecific associations differed between eastern quoll (Dasyurus viverrinus) residents and reinforcers at a conservation-fenced haven. We used GPS collars to quantify distances travelled per night, home and core ranges, nocturnal (activity) and diurnal (denning) habitat use and preference, and conspecific associations over three periods: baseline (residents only, days 3–21), release (both cohorts, days 22–32), and settlement (reinforcers only, days 33–52) for ≤ 42 days post-release (depending on GPS unit longevity). Eastern quolls travelled greater mean distances per night (< 2.15 km, x̄ 1.75 km) and had larger home ranges (< 251 ha, x̄ 178 ha) during the release period. Reinforcers had larger home ranges (249 ha) and greater overlap with other collared eastern quolls (115 ha) when compared to residents (range 90 ha, overlap 46 ha). We found a significant preference for grassland habitat across all animals and periods. During the settlement period, we found a preference for nocturnal activity in greater understory and south-west facing aspects, and lower movement correlation, sociality, and den sharing between collared eastern quolls. Finally, we found lower den sharing in reinforcers (29%) compared to residents (52%), and for fawn- animals compared to dark-morphs. Our results revealed short-term movements, habitat use, and conspecific associations at a greater spatiotemporal resolution than has ever been achieved for this species. Our findings offer important insights into the importance of appropriate habitat and conspecific cueing for reintroductions, and highlight the need to monitor density-dependent mechanisms to inform adaptive management to promote positive outcomes for both initial reintroductions and reinforcements.