Sex determination in-ovo as a population management tool for the Southern Cassowary and Coastal Emu

Abstract

Australia has lost two species and one subspecies of ratite due to historical persecution and anthropogenic changes to their habitats. Two additional ratites, the Southern Cassowary (Casuarius casuarius johnsonii) and Coastal Emu (Dromaius novaehollandiae), are following this trajectory and will require human intervention to prevent further population decline or extinction. Advanced reproductive technologies offer promising avenues for the management of genetic and demographic diversity, both in-situ and ex-situ. Here, we review two important techniques and their efficacy in the conservation management of Australian ratites. The first is the sexing of an embryo in-ovo. This technique is central to developing technologies, however, is presently problematic in species producing thick and heavily pigmented eggs (i.e. Cassowary and Emu). Developments including the reduction of the shell membrane may promote light refraction and thus render the technique able to be used safely with developing embryos of Australian ratites. The supplementation of natural hormone during early embryonic development is another tool for sex regulation in ratite embryos. This was previously trialled in the Ostrich to influence a preferred gonadal sex, however, it will be trialled in the Emu and Cassowary for the first time. The use of these advanced reproductive technologies will complement current conservation efforts for Australian ratites, and facilitate the establishment and maintenance of robust captive populations.