Early in the morning last year, the Freelance writer Kaitlyn accompanied first responder Moe Flannery on a call about a dead humpback calve in California. In great detail, she describes how the necropsies on dead stranded mammals can tell tales about their lives and deaths.
From the outside, not much can be told about the animal unless the carcass shows greater injuries. For larger animals, necropsy is often performed on-site instead of a laboratory, as the effort would be too big. Setting to work immediately, the first responder team starts to cut through the skin and blubber down to the intestines and bones. Bone fractures can indicate impact or trauma, either already healed or possibly fatal. While the content of the intestines shows the last meals, deeper drilling into the bones back in the laboratory can show what the animal has been feeding on for the most of its life, based on stable isotopes. Earplugs and soft tissues like blubber can be analyzed for contaminants and possible pollution risks. Additionally to the earplugs, the baleens can provide a 15-year record of the animal’s life history: hormones indicate when it bred, when females were pregnant and gave birth. Lastly, a tooth cut open can reveal the animal’s age. Samples are taken, frozen, analyzed and stored in the Academy. Since complete bones and structures are usually too big and hard to store, only the pelvic bone is taken for comparison in this case. The humpback whale in question was found with a head trauma, consistent with a ship strike and was mainly nourished by krill.
Such records are incredibly important in understanding the change within mammal populations. Comparisons between samples of stranded grey whales from the last decade and the current year show that many of the animals washed ashore on the west coast were malnourished and skinny. Potential reasons for the ‘unusual mortality event’ could thus be a shortage of food due to warming in the Arctic Seas or due to overpopulation. As for the humpback whales, comparisons of the samples have shown that the mammals have shifted their main food source to anchovies which is congruent with the observation of more inshore feeding. Without such samples taken over long timeframes, population changes and uprising risks and threats like pollution would be hard to identify and counteract.
“A necropsy is like pressing rewind on the camera. […] With enough poking and prodding, we can develop a snapshot of how these magnificent animals died, but also how they lived.”
The detailed story can be found here: https://baynature.org/2020/04/30/a-whales-death-shows-us-the-way-marine-giants-live/
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