Introduction

With many species experiencing population declines, long-term maintenance of captive populations and their re-introduction is increasingly advocated as an approach to species conservation. However, to date, the vast majority of these programs have met with limited success. The lower quality of captive released animals, relative to wild counterparts, appears to be a key factor reducing recovery of endangered species. Released captive-bred animals often under perform in both survival and reproduction, which are direct consequences of inbreeding and being reared in captivity for multiple generations.

Reduced fitness of captive released animals delays or prevents overall recovery of populations. Despite these challenges, captive breeding programs continue to be proposed for recovery of threatened species. Consequently, there is a need to develop husbandry techniques that assess and reduce the "fitness costs" of captivity on wildlife post-release.  This project seeks to establish experimental captive populations for reintroduction that enable assessment of the short- and long-term costs of inbreeding and adaptation to captivity.

Captive breeding and reintroduction programs are a high profile but controversial conservation tools because of the increased risk they can add to species’ recovery efforts. This increased risk appears strongly linked with (1) inbreeding and (2) the habituation/adaptation of wild animals to captivity. Captive breeding permits intensive production of native animals, from a small founder population, by providing an environment less complex, more opimal and predictable, and offering a subset of ecological interactions relative to nature. Captivity not only releases native animals from wild-type selection pressures but can also change the direction of selection, or even impose completely novel pressures on individuals. Typical ways for captive selection to alter animals is to modify or remove behaviours that have little use in captivity, but which are essential in nature (eg. anti-predator behaviour). Changes to physiology and morphology may also occur, rsulting from reduced genetic variation due to founder effects, drift, inbreeding and as selection for captive persistence ensues.

Currently there is a poor understanding of the tempo at which captivity induces inbreeding and selection on native species to alter fitness traits desirable in the wild. Captive breeding programs for threatened native species commonly exceed 10 generations, potentially time enough for significant inbreeding depression and rapid evolutionary change. Once released is there a point (i.e. generations in captivity) that captive-bred animals become sufficiently inbreed and/or maladapted to their native environment that they are unable to aid population recovery? For captive breeding programs to be more successful, experimental husbandry techniques must be developed that specifically: (1) identify the rate at which fitness is lost and (2) maintain individual fitness above such thresholds sufficient to improve population recovery.      

Objectives

This research project aims to establish experimental captive breeding populations of the Agile Antechinus (Antechinus agilis), as an analogue to monitor fitness changes arising from captivity in threatened species. Using these populations, the project has four key objectives:

1. To understand the temporal dynamics by which behavioural, physiological, genetic and life-history processes of a population are changed in captivity.
2. To understand the tempo at which inbreeding reduces fitness in captive populations.
3. To independently quantify the temporal consequences of inbreeding and captive selection-related changes to the fitness of captive-released animals relative to wild bred animals by comparing their respective demographic (survival, dispersal) and reproductive contributions (via genetic paternity assessment) to wild population dynamics.

Anticipated Benefits and Outcomes

Captive breeding programs, whilst widely advocated, are currently faced with key challenges of producing both sufficient and high quality animals for release. This project could provide several important generic outcomes for improving the performance of captive breeding programs, including: (1) detailing the consequences and the time frame (i.e. generations) by which captivity can alter the biology of native animals, (2) the impact of such changes on the fitness of individuals released back into the wild and (3) the capacity for experimental husbandry manipulations to influence genetic (eg. founder effects, inbreeding) underpinning generic problems associated with captive breeding programs. The benefits of this knowledge would enable:

1. Contribute to making more informed decisions about the efficacy/risk/benefit of captive breeding and reintroduction programs for threatened species recovery;
2. Development of husbandry protocols that would improve retention of wild attributes in threatened species;
3. Set a precedent for better integrating captive and field components of the recovery process for threatened species which currently often function with little biological feedback between them; and
4. Improve the capacity of captive breeding programs to deliver there intended conservation benefit of aiding recovery of threatened populations and species.