Amanda CHONG Characterisation of endogenous retroviruses in the saltwater crocodile (Crocodylus porosus) Endogenous retroviruses (ERVs) are a diverse group of vertebrate transposable elements, and are derived from germline infections by exogenous retroviruses. Very few studies have been carried out investigating the diversity of ERVs in non-mammalian vertebrates despite evidence that these species harbour a diverse and divergent ERV complement. This project constitutes the first comprehensive investigation of endogenous retroviruses (ERVs) in crocodilians. The research presented herein encompasses the characterisation of crocodilian ERVs from key crocodilian species, and explores the evolutionary dynamics of these ERVs within their host genomes. It also offers insights into the evolution of ERVs and exogenous retroviruses. Overall, this project has demonstrated that crocodilians, and likely other non-mammalian vertebrates, are a rich source of novel ERV diversity, and may provide unique insights into the evolution of modern exogenous retroviruses and their hosts. It has also highlighted the relative merits of a wide variety of ERV detection techniques, both molecular and bioinformatic, and how these may be adapted for studies of previously uncharacterised taxa. This project will provide a useful resource to facilitate further investigations into the significance of ERVs in crocodilian biology, and offers insights into how these approaches may be translated to studies of other vertebrate taxa.