Conservation efforts to secure the long-termsurvival of crocodilian specieswould benefit fromthe establishment of a frozen sperm bank in concert with artificial breeding technologies to maintain genetic diversity among captive assurance populations. Working towards this goal, our research has focused on the saltwater crocodileCrocodylus porosus as a tractable model for understanding crocodilian sperm physiology. In extending our systematic characterisation of saltwater crocodile spermatozoa, in this studyweexamined the development of motility during spermtransport through the excurrent duct system of the male crocodile. The results show that approximately 20% of crocodile testicular spermatozoa are immediately motile but experience a gradient of increasingmotility (percentagemotile and rate of movement) as they transit themale reproductive tract (epididymis). Moreover, we confirmed that, as in ejaculated crocodile spermatozoa, increased intracellular cAMPlevels promoted a significant and sustained enhancement of sperm motility regardless of whether the cells were isolated from the testis or epididymis. Along with the development of artificial reproductive technologies, this research paves the way for the opportunistic recovery, storage and potential utilisation of post-mortem spermatozoa from genetically valuable animals. [ABSTRACT FROM AUTHOR]