Imaging and Diagnostic Tools for Cetacean Mammary Gland Assessment: Challenges and Future Directions for Marine Mammal Pathology, Medicine and Research

Reproduction studies are important for the conservation of cetaceans (whales, dolphins, and porpoises) because they provide essential information for assessing populations and species dynamics, particularly in relation to the management of the diverse cetacean species in human care. A vast majority of literature on the female cetacean reproductive anatomy and physiology has focused on the ovaries, which can be used to infer reproductive history, or genital diseases and anomalies. However, literature regarding the morphology, physiology, and developmental pattern of cetacean mammary glands is scarce, despite their fundamental role in providing vital nutrients for the growth of offspring. This review describes current diagnostic tools applied in human and veterinary medicine to assess mammary glands and how marine mammal medicine could benefit from incorporating these tools into standard evaluation of the mammary glands in free-ranging and captive cetaceans. By evaluating the strengths and weaknesses of the current tools used to assess the mammary glands in humans and domestic animals —such as mammography, CT, MRI and ultrasonography— we frame a collection of diagnostic approaches that might be adapted to the particular challenges faced by marine mammal veterinarians, to enhance the evaluation of cetacean mammary gland morphology, physiology and development.