84,673 research outputs found

    Sheep, dingoes and kangaroos: new challenges and a change of direction 20 years on

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    Predation and competition are two primary forces limiting the extent to which sheep can be grazed in the Australian rangelands, particularly in Queensland. Dingo predation has been non-existent in much of the sheep zone since the localised eradication of dingoes in the early 1900s. Competition with kangaroos has been ever-present, but was previously managed (to some extent) by the commercial kangaroo harvesting industry. However, changes to dingo distribution and kangaroo densities and harvesting over the last 20 years have meant that dingo predation and kangaroo competition again threaten viable sheep production in the rangelands. Dingoes have increased their distribution and density in almost all sheep grazing areas and contemporary lethal control efforts are not preventing the decline of sheep. Loss of valuable international markets and moves to now harvest only adult male kangaroos means that the kangaroo harvesting industry produces little relief from kangaroo grazing pressure (given that kangaroo population growth is little affected by removal of adult males; see Finch et al. this volume). New approaches to dingo and kangaroo management are sorely needed to salvage and restore the production of sheep in the rangelands. In response, the installation and use of pest-proof fences is rapidly increasing in Queensland and other areas, facilitating, for the first time in nearly a century, the localised eradication of dingoes and the suppression of kangaroos to manageable numbers within fenced areas. We describe these challenges and opportunities for one site in particular (Leander Station), and offer a sheep grazier’s perspective on past and future use and management of problematic wildlife in sheep production zones

    Euclidean Quadratic Forms and ADC Forms I

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    Motivated by classical results of Aubry, Davenport and Cassels, we define the notion of a Euclidean quadratic form over a normed integral domain and an ADC form over an integral domain. The aforementioned classical results generalize to: Euclidean forms are ADC forms. We then initiate the study and classification of these two classes of quadratic forms, especially over discrete valuation rings and Hasse domains.Comment: 26 page