Establishment of an Endangered Species on a Private Nature Refuge: What Can We Learn from Reintroductions of the Bridled Nailtail Wallaby Onychogalea Fraenata?
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Establishment of an Endangered species on a private nature refuge: what can we learn from reintroductions of the bridled nailtail wallaby Onychogalea fraenata? L ISA K INGSLEY,ANNE G OLDIZEN and D IANA O. FISHER Abstract Translocation and reintroduction are used to (Johnson, 2006; IUCN, 2010). Major causes of decline reduce extinction risk associated with a small population have included habitat change from land degradation by and range size in threatened mammal species. We evaluated livestock, particularly sheep, and introduced predators such the outcome of a reintroduction of the bridled nailtail as feral cats Felis catus and red foxes Vulpes vulpes (Fisher wallaby Onychogalea fraenata to Avocet Nature Refuge, a et al., 2003). Because many remaining threatened mammal private refuge in central Queensland, Australia. This populations are small and geographically restricted, in situ macropod was also reintroduced to Idalia National Park management strategies to halt further declines may not be in western Queensland in 1996 and occurs in one natural enough to recover populations of many species in the long population in central Queensland. We estimated population term. We also need to establish new populations to growth, adult and juvenile survival, and distribution distribute the risk of chance disasters (Seddon et al., 2007). changes since the last release of O. fraenata to Avocet in Translocation and reintroduction are common conser- 2005, and evaluated female reproductive success and health. vation strategies, especially for mammals and birds (Fischer Although animals were in good condition, population size & Lindenmayer, 2000; Armstrong & Seddon, 2008). Cross- was a tenth of that of the 1996 Idalia reintroduction reported species comparative studies show that reintroductions often after 3 years and, unlike at Idalia, juvenile survival at Avocet fail to establish self-sustaining populations (Veltman et al., was low. The likely causes are consistent with predictors of 1996; Wolf et al., 1996, 1998; Fischer & Lindenmayer, 2000). translocation and reintroduction failures in mammals. Seddon (1999) and Seddon et al. (2007) suggested that These are predation, the small number of individuals in success should be measured by the survival and successful each release, the likely suboptimal health status of reproduction of the released animals and their offspring, reintroduced individuals, drought, and possibly lack of and the persistence of a self-sustaining population. How- dispersal from the small area of preferred habitat. The ever, the success of translocations is not often assessed, lessons of this reintroduction are that future attempts are especially after the initial period of establishment (Seddon likely to have the best chance of success if they occur in non- et al., 2007). Some of the most important factors associated drought years, at sites with large, non-fragmented areas with successful translocations and reintroductions are: of brigalow forest, involve the release of large groups of (1)sufficient knowledge of the natural history of the species animals together, and are accompanied by intensive, long- to inform the choice of a suitable site, (2) knowledge of the term baiting to control introduced predators. cause of decline and elimination of this threat at the reintroduction site (Wolf et al., 1996; Fischer & Linden- Keywords Australia, Avocet Nature Refuge, bridled nailtail mayer, 2000), (3) selection of appropriate age classes, sex wallaby, ex situ conservation, Macropodidae, Onychogalea ratios and healthy individuals for release (Pople et al., 2001; fraenata, reintroduction, translocation Robert et al., 2004; Letty et al., 2007), and (4) establishing populations in the core of a species’ historical range (Wolf et al., 1998). Introduction The bridled nailtail wallaby Onychogalea fraenata is a medium sized (4–8 kg), solitary, nocturnal species that now bout a third of all modern mammal extinctions have inhabits , 1% of its former range and is categorized as occurred in Australia during the last 150 years A Endangered on the IUCN Red List (McKnight, 2008). Possible causes of decline include vegetation clearing (resulting in , 10% of the species’ original habitat re- LISA KINGSLEY*,ANNE GOLDIZEN and DIANA O. FISHER (Corresponding author) maining), introduced predators (red foxes and feral cats), School of Biological Sciences, Goddard building (8), The University of and vegetation degradation by introduced herbivores, Queensland, School of Biological Sciences, St Lucia 4072, Queensland, Australia. E-mail d.fi[email protected] particularly sheep and cattle, and perhaps rabbits (Gordon 1980 *Current address: 7610 Ridgecrest Drive, Alexandria, Virginia, 22308, USA & Lawrie, ). O. fraenata was presumed to be extinct from c. 1932 until its rediscovery in 1973 on a cattle property Received 18 November 2010. Revision requested 25 January 2011. Accepted 15 March 2011. in central Queensland (Gordon & Lawrie, 1980). The © 2012 Fauna & Flora International, Oryx, 46(2), 240–248 doi:10.1017/S0030605311000652 Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.76, on 27 Sep 2021 at 20:39:35, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605311000652 Reintroduction of Onychogalea fraenata 241 property was purchased by the Queensland National Parks Service and is now Taunton National Park (Scientific), containing the sole remaining wild population of this species. The population was estimated to be . 1,000 during 1986–1990 (Tierney, 1985; Evans, 1992) but declined fol- lowing a severe drought in 1992–1994 to , 500 (Fisher et al., 2000, 2001), and has continued to decline in size and distribution. Reasons for the current decline at Taunton National Park (Scientific) are unknown but are probably combinations of changing vegetation reducing the avail- ability of preferred food and shelter, increased predation by dingoes and cats during droughts, and chance effects of small population size (Fisher et al., 2000, 2001). A reintroduction of bridled nailtail wallabies to Idalia National Park in western Queensland commenced in 1996. During 1996–1999 133 individuals sourced from a captive breeding colony and from the Taunton population were released. There was intensive predator control, monitoring to detect predator incursions, establishment of a fenced breeding colony, release of animals born on the site as well as wild-born animals, and regular monitoring (Pople et al., 2001). The reintroduction was considered to be a success in 2001 because the population had increased to 400 (Pople et al., 2001). In 2001–2005 there was a further reintroduction, at Avocet Nature Refuge. This is an area of privately-owned land, designated as a nature refuge under a Voluntary Conservation Agreement with the Queensland government. This refuge contains c. 90 cattle and is c. 120 km south-west of Taunton National Park (Scientific). The aim of the study reported here was to determine whether the reintroduction FIG. 1 Map of the eastern third of Australia showing locations at Avocet Nature Refuge has succeeded in establishing a self- of historical records of the bridled nailtail wallaby Onychogalea sustaining population. fraenata, and current populations at (1) Avocet Nature Refuge, (2) Taunton National Park (Scientific), the sole wild population, 3 4 Study area ( ) Idalia National Park, and ( ) Scotia Sanctuary. Gregory mine site is indicated by a black triangle (5). Adapted from Lundie- 2005 The 565 ha Avocet Nature Refuge (Fig. 1) contains suitable Jenkins & Lowry ( ). Points indicating the location of sites habitat (see below) and falls within the historical range of are not to scale. O. fraenata. Mean annual rainfall is 574 mm, lower than at Taunton National Park (Scientific) (692 mm) but higher a captive breeding enclosure (Gregory mine site, in central than at Idalia (451 mm). The beginning of the study (2001– Queensland, founded from 16 captive-bred animals in 1997). 2003), when most of the releases took place, was a time of Ninety-seven wallabies were moved directly from the severe drought in central Queensland (Fig. 2). Rainfall Gregory Mine enclosure to two predator-proof holding increased throughout the study, and 2007 and 2008 were pens (50 × 50 m), 1 km apart, for 1 week before release, years of above-average rainfall. between 2001 and 2003 (Table 1). The remaining 69 Vegetation structure and floristics in Avocet Nature wallabies had parasite infestations and were in poor health Refuge are similar to those at Taunton National Park (Old et al., 2009) and were treated at a nearby animal care (Scientific), including brigalow Acacia harpophylla, the main facility (Marlborough) before release. habitat of O. fraenata. Feral cats, dingoes Canis lupus dingo and red foxes occur in Avocet. There is no predator baiting o Methods monitoring but during 2004–2008 51 cats and five foxes were shot on the refuge by Hunting and Conservation Queens- Spotlighting land, a volunteer organization that visits twice per year. In 14 releases from 2001 to 2005 166 O. fraenata were We surveyed O. fraenata at Avocet in May and July 2008. reintroduced to Avocet (Table 1). These wallabies came from We refer to the data collected during these surveys as this © 2012 Fauna & Flora International, Oryx, 46(2), 240–248 Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.76, on 27 Sep 2021 at 20:39:35, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605311000652 242 L. Kingsley et al. FIG. 2 Monthly rainfall record between January 2001 and December 2008 at Emerald, c. 30 km from Avocet Nature Refuge (Fig. 1). Arrows show months in which O. fraenata were released. Mean annual rainfall at Emerald is slightly less than at Avocet (558 mm). The study period began in a time of severe drought; cumulative rainfall deficiency in central Queensland was severe in 2002, Avocet and surrounding areas experienced , 5% of the historical rainfall mean in 2002–2003 (BOM, 2003). Annual rainfall increased during the study period, and 2007 and 2008 were years of above-average rainfall.