Boom and bust – population ecology

Abstract

When Europeans settled Australia, the burrowing bettong (Bettongia lesuew-) was widespread and abundant. It occurred in western New South Wales and Victoria, all of South Australia, the southern half of the Northern Territory and much of the eastern and north-western reaches of Western Australia) with isolated populations in the woodlands of the south-west. However, it declined rapidly and was probably extinct in New South Wales and Victoria by the end of the 19th century, in South Australia by the 1950s, in the Northern Territory by the 1960s and in mainland Western Australia by the 1940s, persisting only on islands off the Western Australian coast. While the burrowing bettong declined, the introduced European rabbit (Oiyctolagus cumculus) and red fox (Vulpes vulpes) expanded rapidly in range and numbers. The first big release of rabbits was in Victorian in the late 1850s to establish populations for hunting. Despite belated attempts at control, they had spread across the southern two-thirds of Australia by the early 20th century, damaging native vegetation and crops and accelerating soil erosion. Foxes were also introduced for hunting near Melbourne, Victoria, in 1845 and 1860. They bred and dispersed rapidly, encouraged by the proliferation of rabbits as food. Foxes now range across much of Australia except the tropical north and many offshore islands, including recently Tasmania. Foxes are a significant cause of decline in native mammals (Chapter 2), an agricultural pest and a potentially important reservoir for rabies should the disease reach Australia. Population ecology, the subject of this chapter, seeks reasons for phenomena such as the calamitous decline of the burrowing bettong and the rapid increase in the rabbit and fox Populations. Chapter aims: In this chapter we describe the properties of populations, the methods for measuring their key features (density, size, recruitment, deaths and migrations)) and how techniques differ for plants and animals. We discuss the factors influencing population growth, and illustrate practical applications of population ecology for fields such as pest control, conserving endangered species and harvesting natural resources.