Sudden and rapid decline of the abundant marsupial Bettongia penicillata in Australia

Abstract

The woylie Bettongia penicillata is categorized as Critically Endangered, having declined by c. 90% between 1999 and 2006. The decline continues and the cause is not fully understood. Within a decline diagnosis framework we characterized the nature of the decline and identified potential causes, with a focus on the species' largest populations, located in south-west Western Australia. We described the spatio-temporal pattern of the decline, and several attributes that are common across sites. We categorized the potential causes of the decline as resources, predators, disease and direct human interference. Based on the available evidence the leading hypothesis is that disease may be making woylies more vulnerable to predation but this remains to be tested. No substantial recoveries have been sustained to date, and one of the three remaining indigenous populations now appears to be extinct. Therefore, verifying the factors causing the decline and those limiting recovery is becoming increasingly urgent. Active adaptive management can be used to test putative agents, such as introduced predators. Insurance populations and ecological monitoring should also be included in an integrated conservation and management strategy for the species.

Lethal 1080 baiting continues to reduce European Red Fox (Vulpes vulpes) abundance after more than 25 years of continuous use in south‐west Western Australia

“…; Wayne et al . ). We address two questions relating to baiting effectiveness: (i) are baits available and acceptable to foxes and (ii) does the baiting programme at DW and TNR induce high fox mortality and reduce density relative to unbaited sites?…”

“…Three explanations for the recent Woylie declines have been proposed (Marlow et al 2015a): (i) reduced effectiveness of fox control; (ii) the effects of disease; or (iii) replacement of foxes by other predators in the presence of effective fox control. Here, we investigate the efficacy of the fox baiting regime because the roles of disease and of alternative predators are explored elsewhere (Pacioni et al 2014;Marlow et al 2015a;Wayne et al 2015). We address two questions relating to baiting effectiveness: (i) are baits available and acceptable to foxes and (ii) does the baiting programme at DW and TNR induce high fox mortality and reduce density relative to unbaited sites?…”

Identifying factors that influence stress physiology of the woylie, a critically endangered marsupial

“…Remnant populations are now confined to Western Australia (Wayne et al, 2013a). Recent studies suggest that the distribution and abundance of woylies is related to stressors including habitat fragmentation, proximity to agriculture and invasive predators (Wayne et al, 2013b;Yeatman et al, 2016). In addition, more virulent trypanosomes (protozoan hemoparasites) have been found more commonly in declining woylie populations (Botero et al, 2013;Thompson et al, 2014), and white blood cell counts in declining populations are suggestive of 'immunological stressors' (Pacioni et al, 2013).…”

Genetic diversity loss in a biodiversity hotspot: ancient DNA quantifies genetic decline and former connectivity in a critically endangered marsupial

“…peak of about 200 000 animals in 1999 . The factors responsible for this decline are still not well defined (Groom 2010;Wayne et al 2015). Recent genetic studies of the extant populations using microsatellite data from 231 live individuals revealed four genetically distinct wild populations (Pacioni et al 2011).…”