by Dr Viyanna Leo, Wildlife Ecologist
Located in Sydney Harbour, North Head is a site of high ecological value. It protects a range of threatened plant and animal species including an important population of the Long-nosed Bandicoot (Perameles nasuta) and a significant remnant of the critically endangered Eastern Suburbs Banksia Scrub.
At North Head, Australian Wildlife Conservancy works in partnership with Sydney Harbour Federation Trust (SHFT), which manages the area, to deliver a suite of science projects that protect and enhance conservation values. AWC has provided scientific services to SHFT since 2009 and, in 2013, agreed on a program of biodiversity conservation and restoration at North Head. In 2018, this agreement was extended to 2022, indicative of a successful and productive partnership.
Like much of Sydney, North Head has lost a suite of native species since European settlement. AWC’s work at North Head focuses on the conservation of the extant native biota (plants and animals) as well as the reintroduction of locally extinct species. To date, three small native mammal species have been reintroduced to North Head: the Bush Rat (Rattus fuscipes), Eastern Pygmy Possum (Cercartetus nanus) and Brown Antechinus (Antechinus stuartii).The Bush Rat is an important part of the faunal assemblage in forests of south-east and south-west Australia. Bush Rats were reintroduced to North Head in conjunction with the removal of black rats (Rattus rattus), an invasive species which has replaced native rodents in much of the remnant vegetation around Sydney. The successful establishment of Bush Rats will assist in reducing black rat numbers across the headland and benefit other small mammal species being reintroduced.
Results from AWC’s monitoring program indicate that the reintroduction of Bush Rats has been very successful. At monitoring sites, Bush Rats now significantly out number black rats, indicating that Bush Rats can successfully defend territories and out compete the invasive species. In addition, Bush Rats are now detected across the headland, showing that the population has successfully expanded from the original release sites.
The Eastern Pygmy Possum is a tiny nocturnal marsupial that is an important pollinator of Banksias and other native flowering plants. It is listed as vulnerable in NSW due to habitat loss, predation by foxes and feral cats, and changing fire patterns. Due to these threats, the Eastern Pygmy Possum has become locally extinct from some areas, including North Head.
From 2016 to 2018, AWC reintroduced 25 Eastern Pygmy Possums to North Head. Monitoring has shown that the species is becoming established at North Head with successful breeding and establishment of young. However, the number of recaptures is still very low and, for this reason, AWC plans to supplement the population until it is firmly established. AWC has proposed sourcing an additional 30 individuals of the species from a number of regional national parks and state forests. The proposed influx of new individuals sourced from different populations will contribute towards the establishment of a genetically diverse population on North Head.
The Brown Antechinus, a small dasyurid, is the third native mammal that AWC has reintroduced to North Head. This semi-arboreal, carnivorous marsupial feeds on invertebrates as well as being an important pollinator, and like other small mammals is vulnerable to feral predators. A total of 34 Brown Antechinus were reintroduced to the headland in 2017.
Radio-tracking showed high survival of reintroduced individuals, however, Brown Antechinus have been difficult to detect in subsequent monitoring surveys. Occasional records show the species is persisting and breeding on North Head. However, as the Brown Antechinus has a high annual mortality rate (all males die after the breeding season, and females are also relatively short-lived), AWC intends to continue supplementation of this species until establishment of the population on North Head can be demonstrated.
Through the reintroduction of these three species, AWC has increased the native mammal assemblage on the headland from five to eight species.
These wildlife reintroductions are helping to restore the ecological role of pollination undertaken by small native mammals on North Head and in doing so, secure the future of the endangered Eastern Suburbs Banksia Scrub community as well as the native wildlife that find refuge there.