Reproductive Science Methods for Marine Mammals

Marine mammals encompass a wide array of species that have evolved specialized anatomical and physiological traits, enabling them to survive and thrive in the challenging conditions of oceanic environments which are often characterized by abiotic extremes (e.g., temperature, pressure, light) and biotic variability (e.g., food availability, distribution of conspecifics). As human activities increasingly encroach on coastal fringes and extend into even the remotest parts of the ocean, it becomes essential to understand the survival prospects of marine mammal populations. Understanding the rates at which marine mammals reproduce is vital for evaluating their capacity to endure and adapt in a rapidly changing marine world. In this chapter, we explore contemporary methodologies used to study diverse aspects of reproductive science in marine mammals, including direct observation of reproductive behavior and outcomes, endocrine assessments to determine reproductive state, and assisted reproductive technologies designed to enhance reproductive success. We emphasize the latest advances and innovations in reproductive sampling of marine mammals, noting a continuing progression towards noninvasive data collection methods that are driven by new technologies and emerging challenges. Among the most vulnerable in the world due to their unique combinations of function traits are northern right whales, Eubalaena spp., and the dugong, Dugong dugon. Here, these two case studies are presented to illustrate the challenges faced by researchers studying marine mammals in their natural habitats and to showcase the range of technical approaches employed. The North Atlantic right whale, Eubalaena glacialis, is on the brink of extinction through historical overharvest and present-day threats of entanglement and vessel collisions. Environmental disruption to their migratory routes and declining health have led to reduced reproductive rates. On the other hand, the emerging threat to the vulnerable dugong appears to be extreme weather events that affect the availability of their seagrass food sources. Climate disruption, with increasingly severe coastal storms and flooding, poses a risk to the health of coastal seagrass beds, thereby negatively impacting the reproductive success and survival of this species. It is anticipated that climate change will have varied and often severe impacts on the reproduction of marine mammal populations globally, and understanding reproduction in marine mammals has never been more critical.