Biodiversity & Conservation Unit (NRETA)
Charles Darwin University (CDU)
Dr Karen Firestone
Dr. Meri Oakwood
Dr David Pearson (WA Department of Environment and Conservation)
Dr Jonathan Webb (University of Technology Sydney)
Kakadu National Park
Professor Rick Shine (University of Sydney)
Steve Winderlich (Kakadu NP)
University of Sydney
University of Technology Sydney
W.A. Department of Environment and Conservation
Federal Environmental Protection and Biodiversity Conservation (EPBC) Act 2006: Endangered.
Territory Parks and Wildlife Conservation Act- N.T. 2006: Critically endangered. IUCN – 1994: LR near threatened.
The Northern quoll once occupied a broad band across northern Australia but is now restricted to a handful of isolated populations and islands. Quolls were declining prior to cane toad invasion, due to habitat loss, frequent burning, and predation (Woinarski et al. 2010). The recent advance of the cane toad (Bufo marinus) across the Northern Territory has been catastrophic for the northern quoll. Cane toads are highly toxic, and quolls that mouth or attack large toads rapidly die from toad poisoning. Many quoll populations were decimated after cane toads invaded, and quolls have gone locally extinct in many areas of the Northern Territory, including parts of Kakadu National Park (Woinarski et al. 2010).
The Northern quoll (Dasyurus hallucatus) is one of six species in the genus Dasyuridae. Four species of these carnivorous marsupials are found in Australia and two species in New Guinea. The Northern quoll is the smallest of the four quoll species inhabiting Australia. The body is usually brownish grey in colour with white spots and a cream to white underbelly. The tail is covered in straight coarse dark hair with only the occasional white spot on some individuals (Cole and Woinarski 2000). They are distinguished from other Australian quolls by the smaller size, the largely unspotted tail and striated pads on a five-toed hind foot (Braithwaite and Begg 1995). Adults show marked sexual dimorphism, with males averaging 760 g and females 460 g (Oakwood 2002).
Northern quolls are predominantly nocturnal and are both arboreal and terrestrial. They are opportunistic predators, consuming a wide range of prey including invertebrates, frogs, small reptiles, birds, and mammals. They also eat fruit, nectar, and will feed on carrion and human refuse (Oakwood 2008).
Northern Quolls are short lived, with males living for one to two years, while females can live for up to three years. In the Northern Territory, the breeding season occurs in mid-dry season, from late May to early June. Females produce litters of 4-8 young, and offspring remain in their mother’s pouch until they are 8 to 9 weeks old, at which point they remain in their mother’s den while the mother forages at night. Juveniles leave their mother’s den to forage at five months old, whilst still suckling from their mother. Juveniles are weaned at 6 months old, in November to early December, and thereafter they disperse. Due to their small size, juvenile quolls are vulnerable to predation from a wide variety of predators including owls, snakes, dingoes, and feral cats (Braithwaite and Begg 1995, Oakwood 2000).
Northern quolls inhabit a variety of habitats but are most common in open lowland savanna forest and rocky dissected plateau. The Northern quoll once occupied a broad band across the north of the country, but its geographic range was contracting, particularly from lowland savanna, prior to the cane toad invasion (Braithwaite and Griffiths 1994). The geographic range has dramatically declined since cane toads invaded, and the species is now restricted to a handful of isolated populations across the Top End of Australia, and several islands off the N.T. and W.A. coasts (Woinarski et al. 2007, How et al. 2009).
A formal captive breeding and research program was undertaken by TWP in 2006 to prevent the species from going extinct in the Northern Territory. In 2006 the breeding program produced 57 offspring. In 2007, the breeding group numbered 34 pairs with some pairs being sent to other ARAZPA institution to assist with the project. This project provided the opportunity for important research to be carried out, with both in-situ and ex-situ research aspects being investigated.
The primary objectives of the TWP breeding program were to: (1) provide a genetically sound insurance population for the northern quoll and (2) provide an opportunity for researchers to study quoll genetics, reproductive physiology, and to experimentally test novel methods for reducing cane toad impacts on this species.
Territory Wildlife Park began a pilot breeding study in 1998 to record information on northern quoll breeding biology in the case of suspected declines associated with cane toad arrival. Breeding was successful to F2 generation and draft protocols recorded.
As a result of the threat of cane toad invasion to Northern Territory populations, the Island Ark project was led by the Biodiversity Conservation unit of the Department Of Natural Resources, Environment and the Arts (NRETA) in cooperation with traditional owners and scientists. The primary objective was to establish viable sustainable insurance populations on suitable remote, uninhabited, cane toad free islands off the Northern Territory coast.
TWP provided assistance with the processing, veterinary assessment, treatment and micro-chipping, DNA sample collection and temporary housing of 66 quolls which were subsequently released on the toad-free islands. This project was highly successful, and has succeeded in establishing breeding populations of northern quolls on two islands off the north-east Arnhem Land coast. Local traditional owners and Aboriginal ranger groups are currently monitoring these islands to ensure that they remain free of cane toads.
To read more about the island ark project, visit the website below:
Cane toads have caused a precipitous collapse of northern quoll populations across the Northern Territory. Because it is virtually impossible to eradicate cane toads from the wet-dry tropics, we need to develop an alternative solution to the cane toad problem. Rather than trying to eradicate toads, it may be possible to manipulate the behavior of predators so that they can coexist with cane toads.
In 2008, researchers from the University of Sydney (Stephanie O’Donnell, Dr Jonathan Webb, and Professor Rick Shine) investigated whether captive reared northern quolls could be trained to avoid attacking cane toads. The researchers successfully trained captive reared juvenile quolls to avoid attacking cane toads. They did this by feeding the quolls a small, non-lethal, dead toad containing the nausea-inducing chemical thiabendazole. After eating the toad, the quolls became mildly ill, and they subsequently associated the taste and smell of toads with illness, and refused to attack live toads for long periods. This phenomenon is called ‘conditioned taste aversion’, and occurs in most animals. Importantly, a single bout of gastrointestinal illness produces long-lasting aversions to prey in predators (Gustavson and Nicolaus 1987).
Fig. 2. A trained ‘toad-smart’ captive reared quoll sniffs and rejects a live cane toad. See the video on You Tube: http://www.youtube.com/watch?v=114nHM5tBkQ
Encouraged by these preliminary results, TWP staff and University of Sydney researchers fitted both toad-smart and toad-naïve quolls with radio-collars containing mortality sensors. They then released the quolls to the wild in suitable rocky habitats near Darwin, and radio-tracked the quolls to determine their fate. Importantly, the toad-smart quolls had much higher short term survival than the untrained toad-naïve quolls (O'Donnell et al. 2010).
Fig. 3. Researcher Stephanie O’Donnell releasing a toad-smart trained quoll near Mary River Park (left) and radio-tracking a quoll in rocky habitat in Kakadu NP (right). Photos: Jonathan Webb.
These preliminary results suggest that it may be possible to mitigate the impacts of cane toads on northern quoll populations. For example, it might be possible to prevent quoll extinctions by deploying ‘toad aversion’ baits ahead of the cane toad invasion front. Quolls that ate baits would become ill, and would subsequently associate the smell and taste of cane toads with illness, and would reject cane toads as prey. Potentially, this novel approach could prevent quolls from going locally extinct after cane toads invade. Alternatively, it might be feasible to facilitate that recovery of northern quoll populations in the N.T. by reintroducing ‘toad smart’ quolls to toad-infested areas. If female ‘toad smart’ quolls survive and breed, then their offspring will have the opportunity to learn to avoid attacking cane toads.
In a pilot study, TWP staff released trained toad-smart quolls to East Alligator Ranger Station in Kakadu National Park in December 2009 and February 2010. Subsequent trapping by University of Sydney and University of Technology researchers at the reintroduction site has provided some exciting results. Some of the toad-smart captive reared female quolls have survived for two years, and have reproduced, and some of their offspring have also survived to adulthood. These exciting results demonstrate that some of the offspring of ‘toad smart’ females reject cane toads as prey. However, dingoes, wild dogs, and other predators remain a major source of mortality for quolls at this study site. Hence, future management to minimize the threats posed by inappropriate fire regimes and predators is necessary to bring about the recovery of quolls in Kakadu National Park.
Northern Quoll release, Kakadu National Park 2012.
Northern Territory Government, Parks and Wildlife Commission of the Northern Territory