Predation by feral cats key to the failure of a long-term reintroduction of the western barred bandicoot

Short, J. (2016). Predation by feral cats key to the failure of a long-term reintroduction of the western barred bandicoot (Perameles bougainville). Wildlife Research, 43(1), 38-50.

Context: Reintroduction of endangered species potentially places them back in contact with putative factors of historical decline, inadvertently providing the opportunity to evaluate their impact.

Aims: To monitor the long-term progress of a population of western barred bandicoot reintroduced to mainland Australia and to assess factors involved in its eventual local extinction.

Methods: Bandicoots were reintroduced from offshore Dorre Island to the nearby mainland peninsula of Heirisson Prong in 1995. The narrow neck of the peninsula was fenced to exclude foxes and feral cats from a 1200 ha area, but the area was subject to periodic incursions. There was parallel management of a confined but unsupported population in an in situ 17-ha predator refuge. Bandicoots were assessed for abundance, body condition and reproduction two to four times annually between 1995 and 2010. In addition, perceived threatening processes (drought, disease and the abundance of cats, foxes and rabbits) were monitored.

Key results: Bandicoots became well established at the site, spreading to all available habitat. Numbers fluctuated strongly, peaking at ~250 in 1999 and then declining to apparent local extinction (with subsequent re-establishment from the refuge), and at ~470 animals in 2006, followed again by extinction.

Conclusions: Predation by feral cats was implicated as the primary cause of both free-range extinctions and the eventual elimination of all bandicoots from the predator refuge. Other contributing factors in one or more of the declines were a reduction in reproduction and recruitment in bandicoots during a one-in-100-year drought, the impact of overabundant European rabbits on vegetation used by bandicoots for nesting shelter and brief fox incursions at key times.

Implications: Existing methods of control of feral cats are rendered ineffective in the presence of abundant and diverse native fauna and abundant exotic species (particularly European rabbits). In addition, episodic drought in arid Australia intensifies the impact of predation by restricting reproduction of prey species. These factors hamper the attempts of conservation managers to re-establish vulnerable species at sites other than those with the infrastructure and/or management intensity to largely exclude exotic predators (and preferably European rabbits) over the long-term.

Cat threat forces translocation of flightless rail.

Wanless, R. M., Cunningham, J., Hockey, P. A., Wanless, J., White, R. W., & Wiseman, R. (2002). The success of a soft-release reintroduction of the flightless Aldabra rail (Dryolimnas [cuvieri] aldabranus) on Aldabra Atoll, Seychelles. Biological Conservation, 107(2), 203-210.

Humans and introduced mammalian predators have caused local extinctions and range reductions in the rallid genus Dryolimnas (endemic to western Indian Ocean islands); today two subspecies survive, one on Madagascar and one on three islands (ca. 8000 birds) of Aldabra Atoll. Domestic cats (Felis catus) still occur on Aldabra and their presence poses a significant potential threat to the rails. Reintroduction to cat-free islands would significantly improve their conservation status. In 1999, 20 rails were captured and brought to now cat-free Picard Island (the third largest island of Aldabra Atoll). Two rails died in captivity but all 18 remaining birds were released and survived beyond the first breeding season. Eight pairs had bonded and bred successfully within 2 months of release, producing a minimum of 13 chicks. Eleven monitored pairs produced 20 chicks in 2000/2001, with 1-year-old birds breeding successfully. Average chick production was significantly higher in the reintroduced population than in the source population in

both breeding seasons. The reintroduced population at the end of the 2001 breeding season was at least 51, an increase of 283% in 18 months. Around 20 pairs are expected to attempt breeding on Picard in the third season after reintroduction, with excellent prospects for continued, exponential population growth in the medium-term. The soft-release reintroduction protocol allowed monitoring of individual birds’ health before release into the wild. This is believed to have played a crucial role in the success of the reintroduction by allowing individuals to acclimatise and providing additional energetic reserves for the period between release and self-sufficiency. A soft-release is recommended as the conservative and precautionary method of choice for avian reintroductions and translocations.

Teaching wallabies to avoid cats and foxes

McLean, I. G., G. Lundie-Jenkins & P.J. Jarman. 1996. Teaching an endangered mammal to recognise predators. Biological Conservation, 75(1): 51-62.

The possibility of conditioning captive-reared animals to fear predators prior to release into the wild is often discussed, but rarely attempted. Here we show that captive-reared rufous hare-wallabies Lagorchestes hirsutus, a species of marsupial that became extinct in the Australian mainland in 1991, become more cautious after conditioning to fear predators that they will encounter after release. The predators, cats and foxes, are not historical enemies of hare-wallabies, but captive-reared predator-naïve rufous hare-wallabies reacted cautiously to them in captivity, suggesting either some genetic recognition abilities for a generalised mammalian predator, or perhaps that hare-wallabies are simply generally cautious in the presence of an unknown animal. Rufous hare-wallabies became even more cautious after two conditioning techniques were used to teach them to associate a fright with a fox or cat. We suggest that conditioning about predators may be a valuable adjunct to many management programmes involving release of predator-naïve endangered animals.