Experts called it an exceptionally uncommon case after finding a rescued manatee calf in St. Petersburg had propeller gashes, shark bite marks, and a serious chest infection.
The Palm Beach Post reported that the case is giving researchers new insight into how human-caused injuries can leave already vulnerable wildlife exposed to even more danger.
What happened?
When responders recovered the 195-pound calf from the water near Eckerd College in June, it was already suffering from a boat propeller strike, the paper reported.
As treatment continued, the Palm Beach Post said rescuers discovered crescent-shaped teeth marks on the tail and the peduncle, where the tail joins the body. Experts said aggressive encounters between sharks and manatees are highly unusual.
"I cannot think of a case where sharks initiated an attack on a healthy manatee," Save the Manatee Club Executive Director Patrick Rose told the paper. "I have been at this over 50 years and have seen manatees in the presence of sharks hundreds, if not thousands, of times."
Because the calf was found in brackish water, Rose said a bull shark may have been involved, per the Palm Beach Post. Even so, he said sharks usually trail manatees to catch fish stirred up by their movement, not the manatees themselves.
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Zoo Tampa took the calf in for rehabilitation, but it was euthanized about two weeks later, the publication reported.
Director of Communications Sandra Morrison said veterinarians were alarmed by the animal's behavior.
"He would take a quick sip of air and then sink to the bottom, even in shallow water," Morrison recounted to the Palm Beach Post.
Why does it matter?
Rose explained to the paper that shark bites on manatees usually happen when "there is some underlying issue whether the manatee was struck by a boat, or had a wound and the shark took a bite."
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The shark encounter may not have happened if the calf had not first been injured by a watercraft. State wildlife officials estimate that at least 8,350 manatees live in Florida waters.
The Palm Beach Post noted that the animals were downlisted from endangered to threatened in 2017, but they still face major risks, including boat strikes, cold stress, and starvation linked to seagrass losses caused by algae blooms.
Through July, Florida had recorded 419 manatee deaths, including 75 caused by boats and 39 linked to cold stress, the outlet reported.
What's being done?
X-rays and other exams eventually revealed a severe infection in the calf's chest, according to Zoo Tampa's care team. The Palm Beach Post reported that this kind of infection can spread through traumatic wounds and leave infected fluid in the chest, making it harder for the lungs to expand.
Groups continue rescuing and rehabilitating distressed manatees. Rose is also warning the Palm Beach Post that changes to how habitat is considered under the Endangered Species Act could weaken protections for manatees and other Florida species before populations crash.
"That has far reaching consequences and will put many species literally on the brink of extinction before you could take serious action," he told the paper.
The FWC Wildlife Alert Hotline at 888-404-3922 is the number to call if you see an injured, distressed, or abandoned calf.
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