Methods to Examine Reproductive Biology in Free-Ranging, Fully-Marine Mammals

Abstract

Historical overexploitation of marine mammals, combined with present-day pressures, has resulted in severely depleted populations, with many species listed as threatened or endangered. Understanding breeding patterns of threatened marine mammals is crucial to assessing population viability, potential recovery and conservation actions. However, determining reproductive parameters of wild fully-marine mammals (cetaceans and sirenians) is challenging due to their wide distributions, high mobility, inaccessible habitats, cryptic lifestyles and in many cases, large body size and intractability. Consequently, reproductive biologists employ an innovative suite of methods to collect useful information from these species. This chapter reviews historic, recent and state-of-the-art methods to examine diverse aspects of reproduction in fully-aquatic mammals.

Genital interactions during simulated copulation among marine mammals

“…Although mating has not been observed in most species of cetaceans and aquatically mating pinnipeds owing to the logistical challenges of opportunistically observing copulations (e.g. offshore habitats, submerged and out of view of observers; [33]), future studies that document the body alignment of freeswimming cetaceans during copulation are warranted to verify that our simulated copulatory positions reflect real copulatory patterns. In harbour porpoises and occasionally bottlenose dolphin, males have been observed hooking their penises around the female in a dorsal penis-to-ventral vagina orientation (D.N.O., 2016 unpublished data), consistent with our predictions for genital shape correspondence.…”

“…The alignment of the genitalia (e.g. ventral-to-ventral, dorsal-to-ventral) was determined based on the best shape compatibility of the vaginal endocast to the inflated penis tip (figure 1) without a priori consideration of natural copulatory positions, as intromission has not been observed in most species of marine mammals [33]. The interacting penis and vagina were then sewn together to prevent alignment shifts and formalin-fixed in 10% buffered formalin.…”

Mating patterns of dusky dolphins (Lagenorhynchus obscurus) explored using an unmanned aerial vehicle

“…Mating behaviors are challenging to observe in free‐swimming cetaceans (whales, dolphins, and porpoises) that spend most of their lives beneath the surface of the water, often avoid humans, and may occur offshore (e.g., Moore & Clarke, 2002). Additionally, mating events are typically brief and opportunistic (Lanyon & Burgess, 2014; Orbach, Keener, Ziltner, Packard, & Würsig, 2019; Schaeff, 2007). Copulation can serve several nonconceptive functions including play, social learning, and the establishment of social bonds (Mann, 2006), which can confound the understanding of mating strategies.…”

Field Use of Ultrasonography to Characterize the Reproductive Tract and Early Pregnancy in a Phocid, the Weddell Seal (Leptonychotes weddellii)

“…This information would be applicable to other phocid species, which are not as easily accessible for longitudinal study, but may be exhibiting population declines or be considered environmental sentinels. Further, utilizing transrectal ultrasound imaging in combination with blood collection for determination of a suite of hormone levels may provide validations for additional simple and minimally‐invasive ways to detect early pregnancy status (Bergfelt et al, ; Lanyon and Burgess, ).…”