2025 Manatee Mortality in Review
The Florida Fish and Wildlife Conservation Commission (FWC) implements a statewide manatee carcass response and rescue program, providing a wealth of insight into manatee disease and mortality factors. All reported manatee carcasses, regardless of salvage or disposition, are documented in the manatee mortality database after verification by FWC manatee researchers. The total statewide manatee mortality number (632) for 2025 was below the average (731) of the five most recent years but was higher than the last two years (2023 and 2024) when 555 and 565 carcasses were recorded respectively. A colder winter, a red tide bloom, and calf- and watercraft-related mortality were the most significant contributing factors to manatee deaths in 2025.
The fluke of a large male calf rescued in Bayboro Harbor, Saint Petersburg is ulcerated and bleached due to chronic exposure to cold. The manatee calf was by itself and in unfavorable habitat away from warm water in January 2025.
January 2025 was significantly colder than normal in most of the State, which caused a rise in cold-related deaths compared to recent years. Cold stress disease was diagnosed in 33 out of 213 necropsied carcasses larger than 150 cm in length with a known cause of death. The number of live cold stressed rescued manatees (16) was also higher than the recent five-year average (12). Manatees can succumb to cold stress when chronically exposed to water temperatures below 68oF, or die from acute hypothermia when temperatures drop into the 30’s and 40’s. Cold-stressed manatees display skin lesions from reduced blood flow to the skin, and undergo a metabolic shutdown which can lead to emaciation, dehydration, and secondary infections. The colder weather also indirectly contributed to elevated mortality in the Homosassa River during the winter months. This water system experienced a decrease in submerged aquatic vegetation and increase in macroalgae following several tropical storm events in 2024. Subsequently, the cold in early 2025 likely increased the local abundance of manatees seeking warm water and/or prolonged their stay, which kept them from moving to areas with seagrass such as Gulf waters. Instead of seagrass the manatees consumed the low fiber macroalgae, which can disrupt the natural gut flora and cause Clostridium bacteria to release lethal toxins. Necropsies demonstrated that this acute lethal natural infection from Clostridium bacteria occurred in at least six manatees. The elevated mortality in this area ceased in April when the weather warmed up.
Fifty manatee deaths were attributed to a red tide bloom in southwest Florida during the winter. Historically, large scale mortality events involving hundreds of carcasses occurred when red tide blooms persisted into the spring and coincided with manatee migration, but fortunately this year the bloom dissipated before the end of winter avoiding a possible catastrophic event. Most of the red ride-related carcasses were in Lee County.
An orphaned male calf from Banana River, Cocoa Beach is prepared for transport to a critical care facility for rehabilitation. White tissue remnants of the umbilical cord and fetal skin folds indicate this was a newborn calf.
The number of dead calves (136) was above the recent five-year average (106) but was lower than documented in 2024 (153). 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. Like last year, many perinatal carcasses were in the Indian River Lagoon (IRL). Following several years of starvation and decreased reproduction associated with the Atlantic coast mortality event, field observations indicated that manatee reproduction resumed when nutritional condition improved in 2023, and many new calves were born in the IRL in the last two years. 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. So far necropsies have not shown any disease or significant new threats in the deceased small calves. The number of small calf carcasses in the Atlantic coast subpopulation (81) decreased from last year (105); however, it is always possible that variables like carcass detection, reporting, and manatee distribution influence such numbers from year to year. Nevertheless, a relatively low number of deaths in larger calves on the Atlantic coast compared to years before the starvation event, and the many live calf sightings reported from the field are an encouraging step towards possible improvement in Atlantic manatee reproductive health.
An adult male manatee with watercraft-related wounds rescued in Kings Bay, Crystal River is resting in a transport truck on his way to a critical care facility.
Mortality from collisions with watercraft remains one of the most significant threats to the manatee population and comprised 25% of causes of death in necropsied carcasses in 2025 (98 cases). This is a minimum number as only a portion of manatee carcasses are fully necropsied based on factors outlined under the FWC stratified random sampling approach. Also, in 50 carcasses a cause of death could not be determined due to decomposition or inconclusive necropsy findings. The FWC and partners rescued 33 live manatees with watercraft-related injuries in 2025, which is the highest number on record.