Reintroducing the red-tailed phascogale (Phascogale calura): insights from 20 years of translocation efforts

Reintroductions are challenging and many fail. The red-tailed phascogale (Phascogale calura) is a small semi-arboreal Australian dasyurid marsupial that has been extirpated from 99% of its pre-colonisation range. Nine reintroductions have been attempted since 2005 across five States and Territories, six into feral predator-free fenced areas (safe havens) from which feral cats and foxes were extirpated, and three into unfenced areas where cat and/or fox control occurs. We summarise the methods and results of these reintroduction attempts to inform future management. Of the nine reintroduction attempts, three were considered successful and support populations extant for more than 5 years (two safe havens and one unfenced), three did not lead to population establishment (two safe havens, one unfenced), two safe haven populations remain extant 2 years after initial reintroduction, and one unfenced reintroduction is still underway. All three successful reintroductions released wild-sourced adult animals, sometimes in combination with captive-bred animals, and were within 280 km of extant wild populations. In comparison, all releases that did not result in established populations primarily released captive-bred animals. The main challenges encountered during red-tailed phascogale reintroductions included predation by introduced and native predators, hyperdispersal, toxoplasmosis, and severe weight loss post-release. All but one reintroduction (Western Australia, safe haven, wild-sourced founders) reported low recapture rates of founders or high mortality of radio-collared individuals, suggesting low initial survival of translocated animals. Red-tailed phascogales may be more challenging to reintroduce and monitor than some other marsupials because of their small size, making them (1) more vulnerable to predation from both native and invasive (i.e. feral cats and foxes) predators, (2) more susceptible to starvation after release, and (3) more likely to hyperdisperse through safe haven fences. Captive breeding may affect the probability of post-release survival through inappropriate anti-predator behaviours, unfamiliarity with food sources at release sites and underdeveloped hunting behaviour, and possibly an increased susceptibility to toxoplasmosis. We recommend that practitioners consider sourcing wild animals for translocations where possible or, if using captive-bred animals, employing rigorous toxoplasmosis assessment and hygiene alongside a staged soft-release strategy involving gradually weaning each release group off supplementary food in situ.