Finding the Balance: Fertility Control for the Management of Fragmented Populations of a Threatened Rock-Wallaby Species

Abstract

Simple SummaryBlack-flanked rock-wallabies (Petrogale lateralis lateralis) can reach high numbers in fragmented populations in the West Australian wheat-belt, where they can damage crops and cause habitat degradation. As they are threatened, we wanted a non-permanent control method that did not adversely affect the body condition of treated females compared to untreated females, using body condition as an indicator of general health and fitness. We gave adult female rock-wallabies deslorelin contraceptive implants to suppress their fertility and monitored the impact for three years. Treated females did not conceive new young for over two years. We did not detect any negative effects on body condition, suggesting that deslorelin may be an effective tool for managing overabundant populations of marsupials.AbstractPopulations of Australian marsupials can become overabundant, resulting in detrimental impacts on the environment. For example, the threatened black-flanked rock-wallaby (Petrogale lateralis lateralis) has previously been perceived as overabundant and thus ‘unwanted’ when they graze crops and cause habitat degradation. Hormonally-induced fertility control has been increasingly used to manage population size in other marsupials where alternative management options are not viable. We tested whether deslorelin, a superagonist of gonadotropin-releasing hormone (GnRH), would suppress reproduction in free-living adult female rock-wallabies without adversely impacting body condition. We trapped, synchronised reproduction and allocated female rock-wallabies to a placebo implant (control, n = 22), one (n = 22) or two (n = 20) subcutaneous implants of deslorelin. Females were then recaptured over the following 36 months to monitor reproduction, including Luteinising Hormone levels, and body condition. Following treatment, diapaused blastocysts reactivated in five females and the resulting young were carried through to weaning. No wallabies treated with deslorelin, conceivede a new young for at least 27 months. We did not observe adverse effects on body condition on treated females. We conclude that deslorelin implants are effective for the medium-term suppression of reproduction in female black-flanked rock-wallabies and for managing overabundant populations of some marsupials.

Rapid population expansion of Boodie (Burrowing Bettong, Bettongia lesueur) creates potential for resource competition with Mala (Rufous Hare‐wallaby, Lagorchestes hirsutus)

“…Macropod overpopulation in fenced reserves is a widespread issue in Australia, with government departments and organisations implementing control programs such as fertility control and one‐way gates to lower population size (Willers et al . 2015; Butler et al . 2019; Moyses et al .…”

“…Macropod overpopulation in fenced reserves is a widespread issue in Australia, with government departments and organisations implementing control programs such as fertility control and one-way gates to lower population size (Willers et al 2015;Butler et al 2019;Moyses et al 2020). At Arid Recovery in South Australia, Boodie (Burrowing Bettong; Bettongia leseuer) populations have been observed increasing within a fenced environment until overabundant, resulting in vegetation damage (Linley et al 2017;Moseby et al 2018) Ecosystems comprise many species with spatially and temporally dynamic relationships.…”