Territory Stories

Debates Day 3 - Thursday 13 February 2014



Debates Day 3 - Thursday 13 February 2014

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Parliamentary Record 10


Debates for 12th Assembly 2012 - 2016; ParliamentNT; Parliamentary Record; 12th Assembly 2012 - 2016




Made available by the Legislative Assembly of the Northern Territory





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Hansard Office

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Attribution International 4.0 (CC BY 4.0)

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Legislative Assembly of the Northern Territory



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DEBATES Thursday 13 February 2014 3441 The Top End of the Territory supports a rich assemblage of native land mammals. However, apart from the kangaroos, wallabies and fruit bats, most of these animals are small, secretive and nocturnal, so do not enjoy a high public profile. People may be aware of possums, bandicoots and quolls, but our unique small mammal fauna also includes many dasyurids. These are small carnivorous marsupials which are relatives of the spotted northern quoll, or so-called native cat, including the diminutive 5 gm planigale, one of the worlds smallest mammals. Top End bush also supports a variety of native rodent species, from the diminutive delicate mouse to the impressive 1 kg black-footed tree-rat. In all, there are 37 native species found in the Top End within the broadly defined group of small mammals I speak about today. A growing body of evidence from the past two decades is showing widespread and severe declines in many native small mammal species in the Top End of the Territory and elsewhere in northern Australia. Much of this evidence comes from Kakadu National Park where there is relatively detailed, extensive and long-term data from research and monitoring studies. However, studies in other Top End parks such as Litchfield, in Arnhem Land, the Daly region, and from the Kimberley and North Queensland, support this as being a widespread phenomenon across northern Australia. The data from Kakadu and Territory parks is particularly alarming in demonstrating that declines are even occurring on lands being specifically managed for conservation. A good illustration of the extent of these declines is provided by data from a large number of long-term monitoring plots in Kakadu National Park, which has particularly rich mammal fauna. Over the past 15 years, the average number of mammal species recorded per site declined by 65% and the average number of individual animals recorded declined by 75%. Significant declines, in some cases close to 100%, were recorded for at least 10 different native mammal species, including bandicoots, possums, dasyurids and rodents. In the fauna assessment surveys regularly carried out by scientists from my department, it has now become common place to catch not a single native mammal. This is in stark contrast to the high numbers found previously. Why are these declines occurring now throughout our extensive tropical savannahs that appear to be largely intact and healthy? The best available evidence suggests declines are caused by a number of factors with complex interactions between them, but the key culprits appear to be fire and feral animals, particularly the feral cat. Other factors such as diseases may play some role, but remain very poorly understood. It is also worth noting that while the spread of the despised cane toad has had a severe impact on a small number of mammal species such as the quoll, it is not the primary cause of most declines. It is well known there have been major changes over the past century in fire regimes experience in our Top End bushland. Fires have generally become more frequent and of greater intensity, particularly during the late Dry Season, and individual fires are more extensive. Apart from direct wildlife mortality from such fires, frequent or intense fires remove ground cover and mid-storey plants and degrade food resources and other important habitat features such as tree hollows. Data from long-term monitoring sites in Kakadu National Park clearly demonstrates that decline in small mammal species tends to be most pronounced in sites that are more frequently burned. However, the data also suggests that fire patterns alone cannot explain the extent and severity of recent mammal declines. Attention is now focused on the role of predators, particularly the impacts of the feral cat. Cats were bought to Australia with European settlement and quickly established in the wild, gradually spreading throughout the continent and occupying almost every ecosystem. A recent estimate puts the number of feral cats in Australia at approximately 15 million. Cats are very effective generalist predators, eating a wide variety of invertebrates, reptiles and small mammals. If we presume cats catch five prey items per day, Australias feral cats are likely consuming a staggering 27 billion animals per year. A recent review of the status of Australias native mammals has ranked the feral cat as the single most significant threat. In the Top End bush, feral cats are ubiquitous, but elusive, and are rarely seen by land managers, so receive little public attention. However, every square kilometre of Top End bush land is likely to be patrolled by a feral cat, as has been recently demonstrated by scientists from my department, using motion sensor cameras to detect cats. Unfortunately, the development of effective methods to control cats through the use of, for example, poison baits similar to those used to control wild dogs, has been slow and difficult. This is exacerbated in northern Australia, where we lack basic knowledge of the ecology and behaviour of feral cats. Our scientists now believe there may be an unfortunate nexus between the effects of fire and of predators such as cats on native small