Implications of mesopredator release for biodiversity conservation, with particular reference to Australian systems

• Main Author: Crawford, H.
• Format: Other/Unknown Material
• Language: English
• Published: Murdoch University. School of Biological Sciences 2010
• Subjects: Myers; Rayner; Ritchie; Antarc*; Antarctica
• Online Access: https://researchrepository.murdoch.edu.au/id/eprint/27896/

In 1988, Soulé et al. observed that chapparal-requiring birds experienced a population decline following elimination of the system’s top predator, the coyote. Exploration of the causes for the crash led the researchers to surmise that following coyote removal, there had been an increase in the abundance of a smaller predator, the red fox. Soulé et al. called this ‘mesopredator release’ and suggested that further research was needed in multiple ecosystems to validate the extent of the phenomenon. Over the last twenty years, mesopredator release has been reported in ecosystems on every continent except Antarctica, including many island, fresh-water and oceanic ecosystems (Myers et al., 2007; Prugh et al., 2009; Rayner et al., 2007; Ritchie and Johnson, 2009; Roemer et al., 2009). These results are now the basis of the mesopredator release hypothesis (MRH), suggesting that apex predators suppress populations of smaller mesopredators, but that these mesopredators are ‘released’ from these pressures if the apex predators are removed, leading to changes in species composition and population dynamics. The MRH is highly relevant to conservation issues in Australia. Australia is the only island continent and, especially since European settlement in 1788 (Jupp, 2001), Australia has been invaded by several species deemed to threaten its native fauna (Burbidge and McKenzie, 1989; Dickman, 1996; McKenzie et al., 2007; Short and Smith, 1994). The interactions between these alien species are not fully understood in the context of Australian ecosystems (Burbidge and McKenzie, 1989; Glen and Dickman, 2005). It has been theorised that the successful removal of one species may trigger mesopredator release and result in an even more devastating effect on native wildlife. It is the main aim of this essay to analyse evidence for mesopredator release in Australia. This requires a detailed understanding of mesopredator release, so the essay opens with a critical assessment of the concept. This concentrates on terrestrial examples and, specifically, studies involving mammals in recognition of Australia’s diverse and unique mammalian fauna. Applying mesopredator release to Australia also requires an appreciation for the unique nature of the Australian environment and the country’s most crucial conservation issues. Finally, I will discuss suggestions for future testing of the MRH in Australian ecosystems.