Hi! I’m currently working on a big, detailed Blackfish rebuttal, which means lots of rabbit holes. I recently started rereading John Hargrove’s book (ugh). He talks about how the original Shamu died of pyometra and septicemia, claiming that it was something that, apparently, would almost never happen in the wild. The obvious implication here is that captivity caused these conditions, and/or that such is common with captive orcas. However, obviously septicemia can be caused by a variety of things, wild or not. As for pyometra, he doesn’t provide other examples of captive orcas suffering pyometra, nor have I been able to find other examples described in peer reviewed literature. It seems that that isn’t particularly common in cetaceans period, whether they’re wild or not, but I’m also not a marine mammal veterinarian. Since you’d know better about cetacean medicine, I was wondering if you knew anything more about this.
Ooh, that'll be interesting! I'd love to read it!
You're correct that Shamu is the only reported case of pyometra in a killer whale, wild or captive. The CRC Handbook of Marine Mammal Medicine makes no mention of pyometra in cetaceans, although it does occur in both wild and captive pinnipeds and has been reported in sea otters and sirenians. Pyometra is typically the result of bacteria migrating up the vaginal tract into the uterus, which at certain times is more susceptible to infection due to normal hormonal fluctuations. Theoretically, anything with a uterus can get pyometra, though some species are more commonly affected than others.
I would hedge to bet that pyometra is rare in cetaceans because of their truly unusual reproductive anatomy. Females have a lot of redundant tissue in their vaginal tract, creating "false cervixes" and overall making it a lot more difficult for anything to reach the uterus.
See all those extra recesses around the cervix?
I did find this case report on a necropsy of a wild short-beaked common dolphin. Pyometra was one of many nasty issues afflicting the poor girl, so it can indeed occur in nature. Since this individual was suffering from co-infections of bacteria and cetacean morbillivirus, she was clearly immunocompromised. It's highly likely Shamu was as well.
Overall, pyometra of cetaceans (including orcas) appears to be quite rare in both the wild and managed care. Shamu was the very first orca intentionally captured for public display, nearly 60 years ago, and only survived six years in captivity before her death at approximately age 10. Virtually nothing was known about killer whale husbandry at the time, so it's not at all unreasonable to assume that poor husbandry, nutrition, and stress negatively impacted her immune function to the point she succumbed to pyometra.
However, it's a weak argument on Hargrove's part to compare the SeaWorld of today (with multiple orcas now in their 30s, 40s, and 50s) to the SeaWorld of the 1960s, and their very first whale at that. Especially using a condition that has not been reported in a captive orca since.