Featured Image Credit: Thrive Wildlife Conservation
By Kira Krall
If you’re into marine biology, you’ve probably been introduced to whale genitalia and more specifically, male genitalia. Penises are external features and are pretty easy to study. And when a species of whale is the largest animal ever on planet Earth, they’re really tough to miss. But what about our lady whales? Whale vaginas have been severely understudied in favor of the male’s more prominent genitalia. One research team decided to start studying the equally important second half of the reproductive equation: whale vaginas.
The team based out of Texas A&M University and NOAA in La Jolla, CA, collected 59 cetacean reproductive tracts from 20 species of whale that washed up onto beaches. Scroll down to see a cross-section of a short-beaked common dolphin’s reproductive system:
What was of particular interest was the various folds found in the vaginal tract. Two theories emerged from this pioneering scientific study: one is that the folds keep out seawater, and the other is that they help the mother control which male whale’s sperm fertilizes her eggs. Image Credit: Dara N. Orbach et. al
Cetaceans tend to be relatively aggressive maters, often with many males simultaneously trying to mate with a single female. The folds could have evolved in response to these coercive male advances.
Cetacean mating often involves at least 2 males. There’s usually a bit of preamble before the males make their move. The southern right whale’s penis, shown above, is more than 13 feet long. Image Credit: Mariano Jedrzejewski
However, since this is the first study of whale vaginas on this scale, conclusions cannot be determined for the reasons behind the length and number of cetacean vaginal folds. Another interesting element is that the vaginal morphology was extremely diverse. Length of vaginal tract, numbers of folds, and length of folds correlated with taxonomic groups, not body size as originally anticipated.
So, we just spent about 200 words talking about whale vaginas. It may seem arbitrary, but understanding the reproductive systems of animals help biologists understand the mating process and how mother animals select fathers, which adds an often overlooked element of “survival of the fittest.” After all, if a mother whale is going to potentially starve herself in order to care for her calf, she’s going to make sure the father’s genes are worth passing on.
More research needs to be done on individual families and why whale vaginas evolved to look and function the way that they do. Read the study here.