2024 Manatee Mortality in Review
The total statewide manatee mortality number (565) for 2024 was well below the average (739) of the five most recent years and was similar to 2023 when 555 carcasses were recorded.
A healthy newborn manatee calf surfaces next to its mother in the Indian River Lagoon in May 2024.
The number of dead calves (154) surpassed the previous highest yearly total (129) that was documented in 2013. Small calves are assigned to the perinatal cause of death category, which includes manatee carcasses that are less than or equal to 150 cm (5 feet) in total length. This category includes a wide range of causes of death, such as cold stress, aborted fetuses, stillborn manatees, orphaned calves or undetermined cause. More than half of the perinatal carcasses were in the Indian River Lagoon (IRL). Following several years of starvation and decreased reproduction during the Atlantic coast mortality event, field observations indicate that manatee reproduction resumed when nutritional condition improved in 2023, and many new calves were born in the IRL in 2024. An increase in perinatal mortality can be expected with a return to reproduction, either through higher pregnancy numbers, more first-time mothers inexperienced in raising a calf, or some females still dealing with metabolic recovery from chronic malnutrition and not able to carry their pregnancy full-term. Preliminary necropsy data did not show any disease or significant new threats in the deceased calves, and the many live calf sightings reported from the field are an encouraging step towards possible improvement in Atlantic manatee health.
Human-related causes such as watercraft- and water control structure-related mortality comprised approximately 30% of causes of death in necropsied carcasses (96 and 17 cases, respectively). The Florida Fish and Wildlife Conservation Commission (FWC) performs a detailed investigation into every mortality reported near a structure, so it is likely that most structure-related deaths were documented. However, in all other cases, only a portion of carcasses was fully necropsied; therefore, the carcasses listed in the ‘Verified; Not Necropsied’ category included an unknown number of watercraft-related deaths, especially on the Gulf coast where a stratified random sampling approach was used in 2024. The seventeen structure-related deaths are the second highest yearly number on record and include manatee carcasses that were crushed, impinged, or drowned in water control structures and navigational locks. The 2024 mortalities occurred at seven different structures. Over the years, manatee protection measures and retrofitting these structures with protection devices have resulted in safer passage. However, other factors can contribute to manatee mortality in structures, such as unsafe operational procedures of a lock or gate, and flooding leading to increased operations or causing extreme water flows and dangerous conditions for manatees navigating a structure. It is also possible that changes in manatee distribution now cause higher traffic through structures and locks that previously did not encounter many animals. The FWC and United States Fish and Wildlife Service continue to work closely with structure managers to address and reduce such deaths.
Florida Fish and Wildlife Conservation Commission staff respond to a manatee stranded near the runway of MacDill Air Force Base in Tampa after flooding from hurricane Helene. The adult male was carried off the field and trucked to a nearby boat ramp, where he was released in Tampa Bay.
Researchers attributed at least one manatee death to hurricane Helene. This carcass was found in a remote wooded area approximately half a mile from the water, almost three months after the hurricane made landfall. This manatee likely gained access to the area due to the storm surge but then became entrapped after the flood receded. It is possible that more manatees died due to the 2024 hurricanes, but a storm-related cause could not definitively be determined in reported carcasses, or carcasses went undetected in remote areas. Between August and December, FWC and partners rescued nineteen manatees that were entrapped after storm floods from hurricanes Debby, Helene, or Milton. Twelve of these animals have been released, and seven are still receiving care at manatee rehabilitation facilities in Florida. All rescues happened thanks to citizen reports to the Wildlife Alert Hotline (888-404-FWCC), which is often a manatee’s only lifeline, especially in remote areas like the Big Bend.