Two Years Into the Manatee Unusual Mortality Event

Since 2020, our state marine mammal, the manatee has been experiencing an Unusual Mortality Event (UME), meaning that unusually high numbers of these animals have died. These deaths have been centered on the Atlantic coast in Florida, namely, the Indian River Lagoon area. Since the manatee is a federally listed (threatened) species under the Endangered Species Act, the Florida Fish and Wildlife Conservation Commission (FWC) and the U.S. Fish and Wildlife Service (FWS) have been responding to this event. The designation of UME indicates that a serious event is going on and allows for a federal investigation to help minimize further deaths, determine the cause of the event, evaluate the effect of the event on the animal population, and evaluate the role of environmental parameters in the event.

From December 2020-present, FWS and FWC estimate a minimum of 1,817 manatee deaths. 1,052 of these deaths were noted in the year 2021. The previous single-year record for manatee deaths was in 2013, with 830 mortalities. Preliminary data from necropsies suggest starvation as the reason for the great majority of these deaths. These data also indicate that a high percentage of manatees had experienced starvation and malnutrition before the winter season (December 2021-March 2022).

Manatees depend upon submerged aquatic vegetation, namely seagrasses and macroalgae as their main food source. The Indian River Lagoon has battled with poor water quality leading to algal blooms and seagrass loss for years. The lack of suitable conditions led to seagrass die-off. Seagrass is a slow-growing, flowering plant, and once lost, requires decades to re-establish.

As part of their emergency response in 2021, FWS and FWC authorized a supplemental feeding trial to provide remaining manatees with a food source and prevent more deaths. While almost impossible to determine how many manatees were fed or how much produce each individual received, FWC reports that the amount of produce provided to manatees during the 2021-2022 season totaled 201,727 pounds.

As winter approaches and the air and water temperatures begin to cool, the opportunity to spot manatees increases, particularly as they aggregate near warm water sources. Now, more than ever, reporting any animals that appear sick or injured is critically important. You can do this by calling the FWC Wildlife Alert Hotline at 1-888-404-FWCC (888-404-3922), #FWC or *FWC on a cellphone or text 847411 with keyword “FWC,” followed by the city and/or county and any information. Other ways you can help include:

  • wearing polarized sunglasses while boating, this makes manatees easier to see
  • abide by speed zones and idle in areas where manatees are present
  • if you see a manatee, look but maintain your distance. Do not interact or disturb the manatee in any way
  • if you live on a waterway, minimize your impacts with respect to water quality by making sure than any lawn clippings or leaves do not enter the water body
  • plant a Florida-Friendly yard

Hopefully, as we ease into the 2022-2023 season, the manatees will be able to find warm places to snuggle up and eat plentiful meals to fill their bellies. To stay apprised of the UME, please visit FWC’s website.


Posted: December 20, 2022


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