Florida manatee deaths are up in 2020. With the pandemic, we don’t know why

For two months, most dead manatees were not recovered or examined. One possible factor in the death toll? An uptick in boat traffic.
A manatee swims near the entrance to Three Sisters Springs in Crystal River in 2014.
A manatee swims near the entrance to Three Sisters Springs in Crystal River in 2014. [ DOUGLAS R. CLIFFORD | Tampa Bay Times ]
Published Aug. 6, 2020

At least 388 manatees have died in Florida this year, slightly more than average, but in about a third of those cases, scientists did not recover the body to figure out the cause.

Blame the coronavirus pandemic.

In April and May, the Florida Fish and Wildlife Conservation Commission suspended necropsies — the process of examining a dead manatee to determine why it died. Spokeswoman Michelle Kerr said the agency was being cautious to stop the spread of coronavirus, keeping staff distanced when possible.

“They were verified, which means they were recorded into the mortality database, and not recovered because of covid quarantine restrictions,” she wrote in an email. “It takes several staff together to pick up a manatee carcass.”

State data show 99 manatees deaths were documented in those two months, and the majority were listed as “verified, not recovered.” Overall this year, known manatee deaths through July 24th are at least 22 above the five-year average. Carcasses were not recovered in more than 130 cases, already above last year’s total.

“What we’re looking at is something that’s closing in on a lot higher year than normal possibly,” said Patrick Rose, executive director of the environmental protection nonprofit Save the Manatee Club. He noted that the multi-year average is boosted by an uncommonly high death toll in 2018, when algae blooms devastated the state. Florida has so far not seen a big Red Tide this year.

The Fish and Wildlife Conservation Commission noted mortality data is imperfect, and not every dead manatee is counted. In one year people might find and report more carcasses than another.

One potential contributor to the death toll this year is an increase in boat traffic when people were searching for socially distant, and legal, ways to escape their houses during the height of the pandemic.

Rose noted after some weeks of residents staying in, there was “quite a lot of boat traffic” in the spring. Rescuers still went out to help injured manatees, he said, and as always they saw evidence of scars from propellers.

The latest state figures show 68 manatees have been rescued through July, including at least 17 hit by watercraft. Five of those were around greater Tampa Bay.

“In the absence of causes such as Red Tide or cold stress, it is possible that the cause of death was watercraft-related in a significant portion of the carcasses that were reported but not necropsied,” Kerr wrote in an email. “While we do not know this exact portion of watercraft-related deaths for carcasses this year, models and historical data do show that boat collisions with manatees are one of the major threats to the manatee population long-term.”

Florida manatees are considered a threatened species under the Endangered Species Act. In 2018, scientists announced a population estimate of between roughly 7,500 and 10,200. More than 600 died last year, with the leading known cause being boat collisions — more than one in five.

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Boaters are supposed to avoid getting too close to manatees or speeding in restricted waters, where they might run over and wound an animal. The number of boating violations — everything from operating without navigational lights or a valid registration to driving recklessly — is slightly below average so far in 2020, according to the Fish and Wildlife Conservation Commission’s law enforcement arm.

Rose, of Save the Manatee Club, said he wonders about what he considers a significant number of deaths marked as perinatal, covering calves that die around the time of their birth. So far, state officials have documented 69 perinatal deaths compared to 49 this time last year. Rose is “trying to dig a little deeper,” he said, to see if changes to the salinity of water or habitat in some areas might be a factor in some of those incidents.

On the upper Hillsborough River in late May, Angela Prosser, 49, found a dead baby manatee wedged against a dock. She called the Fish and Wildlife Commission, she said, but no one came. A day later, the corpse floated away.

“It was gruesome,” she said.

Prosser had been watching the manatees along the river, as well as boaters who she said came too fast, kicking up a wake. Some looped donuts on jet skis. Several residents along the Hillsborough River said they noticed an uptick in traffic during the pandemic.

“It’s not this slow, lazy river anymore,” Prosser said.

The baby was bloated but unmarked, Prosser said. She noticed its mother had a scar on its back.

If you see an ailing or dead manatee, the Florida Fish and Wildlife Conservation Commission asks you to call its hotline at 888-404-3922 (FWCC). You can also dial #FWC on a cellphone. Boaters are urged to avoid passing over shallow seagrass beds where manatees are known to frequent and to keep at least 50 feet away from any manatees they see.