Document ID: chunk:federal_register_of_legislation:F2023L00432:reg:5:p7
Version: federal_register_of_legislation:F2023L00432
Segment Type: reg
Provision Reference: reg 5 (pt 7/8)
Character Range: 77427–80495

Reduction in population resilience and genetic fitness in wild and intensively managed populations
A species whose population size is small and fragmented is more susceptible to extinction than a species whose population size is large and inter-connected. This elevated extinction risk is the result of several different factors:
    * Small populations are more susceptible to chance events that can cause local extinction, which cumulatively can result in species extinction. They are also less resilient to fluctuation in death and reproduction rates.
    * Small populations can have low genetic diversity and are subject to progressive loss of genetic diversity. Less genetic diversity reduces opportunities for evolutionary adaptation and ability to adapt to changes in the environment.
    * A large population that consists of small isolated sub-populations that do not exchange genes is similarly subject to the loss of genetic diversity and its potential consequences.
The factors can combine or operate in isolation to result in an extinction vortex, where the factors reinforce themselves and accelerate a spiral into extinction.
Human-mediated threats have combined to eliminate bilbies over large areas and in other areas to create fragmented or isolated sub-populations, sometimes of unviable size, and likely to contain only a subset of previous genetic diversity. Such sub-populations are less resilient to threats and have a low capacity to adapt and respond to change.
The factors apply to captive, fenced wild and wild populations, but their effect is influenced by the specific circumstances and the nature of management actions. There are a substantial number of bilbies in reintroduced populations and in captive-breeding facilities. These populations vary in their exposure to the pressures of natural selection processes such as predation. Populations on islands or in large fenced areas are protected from fox and feral cat predation, but are otherwise free-living (in other words reliant on their own foraging for survival, exposed to a range of native predators and other environmental stresses); populations in captive breeding facilities are usually protected from predators and environmental extremes, and provided with food and water. Management of these populations includes activities aimed at maintaining genetic diversity (including management of overabundance and assisting long-term gene flow) and adaptive potential (Hayward et al. 2014).

5.8                 Disease
Disease has not been recorded as a threatening process for this species, however disease is identified as a potential obstacle to the recovery of the Greater Bilby (Bradley et al. 2015). Monitoring for disease can be undertaken during normal health checks and when bilby are handled and is required to ensure early disease detection. If disease is detected relevant state and territory protocols and standard operating procedures should be followed. In addition, Wildlife Health Australia maintains an updated contact list for reporting unusual wildlife disease