Byrne, Phillip G. Dr.

<p>An insurance colony was established for the northern corroboree frog at Tidbinbilla Nature Reserve in the ACT, following the annual collection of fertilised eggs from wild populations between 2003 and 2008. Since then, a substantial number of animals have been transferred to Taronga Zoo and a collaborative captive breeding and reintroduction program has been established from a partnership between the two captive institutions and the NSW Office of Environment and Heritage (OEH) (<a href="#_ENREF_6" target="_blank" rel="noopener">McFadden et al., 2016</a>). Captive breeding protocols have been established for the northern corroboree frog, with the first viable clutch of eggs laid in captivity in 2008. As with its sister species the southern corroboree frog (<em>Pseudophryne corroboree</em>) key requirements for achieving successful breeding of this species include adequate temperature cycling that incorporates a winter cooling period prior breeding, and the provision of large breeding tanks containing multiple males to allow for female mate-choice (<a href="#_ENREF_5" target="_blank" rel="noopener">McFadden et al., 2013</a>).</p><p> </p><p><em>Incorporating assisted reproductive technologies</em></p><p>Although the northern corroboree frog has been bred successfully in captivity for a number of years, captive populations display strong mating bias with less than a third of available males contributing to mating success annually. The natural mating system of this species has similarly been shown to exhibit strong mating bias toward a small number of male individuals, so this mating pattern is not unique among captive populations. However, over time, such captive mating biases may lead to a loss of genetic variation in the offspring generated for re-introduction. Between 2014 and 2016, experimental trials were conducted as part of a strategic research collaboration between the University of Wollongong and Taronga Conservation Society Australia, employing hormone-induced spawning protocols to assist the genetic management of the species. Hypothalamic hormones, administered via a single injection, were used to induce spawning in isolated male-female pairs housed together in small aquaria. Hormone administration significantly improved the number of pairs producing viable embryos and total egg number (Silla AJ, McFadden M & Byrne PG, unpublished data). Overall, in excess of 800 viable eggs (from 37 clutches) were generated using ART between 2014 and 2016, which were subsequently released into natural sites in the Northern Brindabella Ranges. Following on from initial experiments, in 2017 our research team developed successful techniques for the topical application of reproductive hormones to induce breeding in the northern corroboree frog in order to further improve animal welfare, and allow ART technologies to be more widely adopted by amphibian captive breeding facilities nationally. <br /><br /></p><p>Incorporating ARTs into existing conservation breeding programs has a number of potential benefits, including: 1) enhanced species propagation, 2) synchronisation of breeding events, 3) increased genetic diversity and adaptive potential of the offspring generated, and 4) better control over breeding designs, including an opportunity for selective breeding of particular genotypes. As a result, ARTs are being increasingly employed by captive facilities to compliment traditional breeding methods and enhance species recovery.</p><p></p>

<p>An insurance colony was established for the northern corroboree frog at Tidbinbilla Nature Reserve in the ACT, following the annual collection of fertilised eggs from wild populations between 2003 and 2008. Since then, a substantial number of animals have been transferred to Taronga Zoo and a collaborative captive breeding and reintroduction program has been established from a partnership between the two captive institutions and the NSW Office of Environment and Heritage (OEH) (<a href="#_ENREF_6" target="_blank" rel="noopener">McFadden et al., 2016</a>). Captive breeding protocols have been established for the northern corroboree frog, with the first viable clutch of eggs laid in captivity in 2008. As with its sister species the southern corroboree frog (<em>Pseudophryne corroboree</em>) key requirements for achieving successful breeding of this species include adequate temperature cycling that incorporates a winter cooling period prior breeding, and the provision of large breeding tanks containing multiple males to allow for female mate-choice (<a href="#_ENREF_5" target="_blank" rel="noopener">McFadden et al., 2013</a>).</p><p> </p><p><em>Incorporating assisted reproductive technologies</em></p><p>Although the northern corroboree frog has been bred successfully in captivity for a number of years, captive populations display strong mating bias with less than a third of available males contributing to mating success annually. The natural mating system of this species has similarly been shown to exhibit strong mating bias toward a small number of male individuals, so this mating pattern is not unique among captive populations. However, over time, such captive mating biases may lead to a loss of genetic variation in the offspring generated for re-introduction. Between 2014 and 2016, experimental trials were conducted as part of a strategic research collaboration between the University of Wollongong and Taronga Conservation Society Australia, employing hormone-induced spawning protocols to assist the genetic management of the species. Hypothalamic hormones, administered via a single injection, were used to induce spawning in isolated male-female pairs housed together in small aquaria. Hormone administration significantly improved the number of pairs producing viable embryos and total egg number (Silla AJ, McFadden M & Byrne PG, unpublished data). Overall, in excess of 800 viable eggs (from 37 clutches) were generated using ART between 2014 and 2016, which were subsequently released into natural sites in the Northern Brindabella Ranges. Following on from initial experiments, in 2017 our research team developed successful techniques for the topical application of reproductive hormones to induce breeding in the northern corroboree frog in order to further improve animal welfare, and allow ART technologies to be more widely adopted by amphibian captive breeding facilities nationally. <br /><br /></p><p>Incorporating ARTs into existing conservation breeding programs has a number of potential benefits, including: 1) enhanced species propagation, 2) synchronisation of breeding events, 3) increased genetic diversity and adaptive potential of the offspring generated, and 4) better control over breeding designs, including an opportunity for selective breeding of particular genotypes. As a result, ARTs are being increasingly employed by captive facilities to compliment traditional breeding methods and enhance species recovery.</p><p></p>