Reproductive Science Methods for Wild, Fully-Marine Mammals: Current Approaches and Future Applications

Determining reproductive rates of marine mammal populations can give insight into their persistence and resilience in changing environments. As our marine environments continue to degrade along developed coastal fringes and as mankind's influences extend across even our widest oceans, there is a concern that the reproductive functioning of marine mammals may be affected adversely. Since many marine mammal species and populations are still in the recovery phase post-commercial harvest, and yet others are endangered or threatened by ongoing pressures, further environmental changes may represent direct or indirect threats to their reproductive potential. In this chapter, we review the current methods employed to investigate various aspects of reproductive science in fully-marine mammals, including direct observation of reproductive behavior and output, endocrinology to determine reproductive state, and assisted reproductive technologies to enhance reproductive outcomes. In particular, we focus on the most recent developments and innovations to reproductively sample marine mammals. Two case studies are presented to illustrate the challenges thrown up to researchers studying free-ranging marine mammals, and to highlight diversity in research approach. The North Atlantic right whale is on the brink of extinction through historic overharvest and present-day entanglement and ship strike. Environmental disruption to their migration routes and declining population health has resulted in reduced reproductive rates. In contrast, the main current threats to the reproductive success and survival of the vulnerable dugong are extreme weather events that affect availability of its seagrass diet. Climate disruption with increasingly severe coastal storms and flooding threaten the health of coastal seagrass beds, and consequently reproductive success and survival of this species. It is anticipated that climate change may have diverse and often serious effects on marine mammal reproduction in populations around the globe.