With habitat destruction and invasive species comes the loss of biodiversity and ecosystem function. Animal translocations and reintroductions are one of the key options available to conserve and restore wildlife populations and ecosystems. Translocation is relatively new within the broader context of conservation and has only become a commonly used scientific tool within the past 40 years, as such, there are no definitive guidelines for best practice. Wildlife translocations and reintroductions are complex, expensive, and time-consuming, often meaning that many of them fail to establish viable populations. The low success rate has been attributed to inadequate knowledge of species-specific behaviour, poor release site selection, environmental pressures, predation, competition and stress. Monitoring populations after reintroduction is important to identify the success or potential causes for failure, to adapt and improve management strategies. Ideally, successful translocation is indicated by the ability of the translocated, or augmented population, to become self-sustaining, free-ranging and viable in the long term. The Bush Rat Project was the first study to translocate and reintroduce the native bush rat (Rattus fuscipes) into Sydney Harbour National Parks (SHNP) in an attempt to restore the ecosystem and reduce invasive species (black rat, Rattus rattus) populations. 100 bush rats (60 females and 40 males) were released in August 2011 into four sites in SHNP. Bush rats were released in familiar groups and 20 animals were radio tracked for two months. Nine trapping sessions were conducted, the last in May 2014. Ear tissue was taken from all bush rats for use in microsatellite genetic analysis. Sibships and parent-offspring relatedness were determined through this process. Prior to bush rat release each of the four sites were intensively trapped for ten nights to remove black rats. Using these methods, factors that influenced bush rat translocation success were examined, including sex, body condition, weight, virus status, dispersal and establishment of home range, genetic relatedness and structure. These factors were assessed in relation to population dynamics and survival rates, breeding success and habitat. Possible biological control of an invasive species via competition was also examined by comparing persistence of bush rats to number of black rats, avoidance patterns and spatial segregation. Success of translocation in this study can be shown through sex, reproduction, body condition, habitat suitability, site fidelity, relatedness and competition. In the initial stages (within the first year), populations of bush rats had established on all sites and juvenile recruitment occurred, indicating survival, growth and evidence of reproduction. Over the entire study period bush rats persisted in three of the four sites but the remaining numbers were low (less than the numbers released), thus maintaining a viable, self-sustaining population would be difficult. Although animals remained after three or four generations, long-term persistence could be affected by major environmental change or demographic stochasticity if populations remain small. Common species are important in ecosystem structure and function. Declines in their abundance and distribution can lead to loss of less common species and ecosystem function. Wildlife restoration and thus ecosystem function can be restored to ecosystems that are biodiversity poor or have a high element of invasive species. Wildlife restoration increases the functional diversity of remnant habitats, making them more resistant to invasion. As well as being far more cost-effective than reactive management in reversing declines, this proactive approach also helps to determine underlying mechanisms that are required for successful translocation, thus, producing best practice for the reintroduction of rarer species. Bush rat reintroduction into SHNP uses the wildlife restoration concept to reintroduce a common species to restore ecosystem function, increase biodiversity and control invasive species. Bush rats are good candidates for translocation and reintroduction, because they are adaptable and not endangered, therefore can be safely used for multiple reintroductions. Bush rats existed in SNHP as recently as 100 years ago and have conspecifics close by in comparable habitats. They can be sourced from original sites and usually display a rapid population recovery. Therefore bush rat characteristics make them ideal for investigating translocation, colonisation, recovery and competition, within a fragmented habitat. The sites in this study are too new, therefore more introductions to stabilise population would assist bush rat persistence if changes in the environment occur. This is supported by other studies that have shown that repeated releases of large numbers of individuals were generally required to successfully establish a translocated population and create a self-sustaining ecosystem where minimal intervention is required. Wildlife restoration via bush rats creates a situation in which less resources need to be invested in ecological management, as the environment will eventually be capable of self-maintenance. Thus, creating a self-sustaining ecology that does not require further interventions. By reintroducing locally-extirpated animals into modified landscapes, wildlife restoration is a proactive approach that will maintain biodiversity, ecosystem function and avoid future species decline.
| Date of Award | 2018 |
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| Original language | English |
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