The Remarkable Journey of Florida’s Manatees: An Evolutionary Tale

FOR IMMEDIATE RELEASE—January 13, 2025
Contact: media@savethemanatee.org, 407-539-0990

Recent news reports and broadcasts have asserted that manatees are not indigenous to Florida, or that they only made their way to Florida’s western coast during the 1950s. These assertions, which rely on limited anthropological documentation, refer to locations where manatees were historically exploited by humans and presume that a lack of evidence implies manatees were not present in some regions. Nonetheless, absence of evidence does not equate to evidence of absence—it is akin to searching for stars during daylight; just because they are not visible does not mean they do not exist. Furthermore, genetic and fossil records suggest that manatees have inhabited Florida for the past 12,000 years.

The Florida Fish and Wildlife Conservation Commission (FWC), the authority managing Florida manatee populations, has developed a manatee timeline that showcases key events and significant facts regarding manatee existence in Florida (https://myfwc.com/education/wildlife/manatee/timeline/). Historical documents indicate that manatees were recorded in Florida as early as the 1500s, with certain details from the Florida Fish and Wildlife timeline coinciding with evidence highlighted in the published material.

Manatee species, including the African manatee and the Antillean manatee, are still being poached by humans (Marsh et al., 2022). Consequently, it is challenging to see these species in their natural environment, and they may adapt by foraging at night to evade encounters with humans (Rycyk et al., 2021). This behavior might clarify why manatee populations in Florida that were subject to hunting are not found in shell middens and are seldom referenced in historical documents.

Moreover, the publication briefly addresses the paleontological record and genetic data, which suggest that manatees have occupied Florida for far longer. Fossil and genetic evidence showcase a rich history of manatees in Florida. Manatees are classified within the order Sirenia, which encompasses the Amazonian, African, and West Indian manatee species. Although Sirenian fossils have been discovered globally, only Florida and the Caribbean contain specimens from every geological epoch over the last 50 million years (Reep and Bonde, 2006). The modern manatee, as recognized today, emerged from the Caribbean approximately 2 million years ago (Domning, 1982).

The evolution of manatees throughout the Pleistocene epoch offers important insights into how environmental shifts influenced their distribution and genetic variability. During the Pleistocene epoch (2.59 million to 11,700 years ago), there were about 20 cycles of extended glacial phases (40,000–100,000 years), succeeded by shorter interglacial intervals of roughly 20,000 years. At the commencement of these warmer phases, Caribbean manatees traveled northward in response to rising water temperatures (Reep and Bonde, 2006). Water currents and thermal barriers isolated these manatees from populations in Mexico and the Caribbean, producing genetic diversity. Fossil evidence suggests that Trichechus manatus bakerorum thrived in Florida and North Carolina approximately 125,000 years ago but failed to endure the last glacial period that commenced 100,000 to 85,000 years ago (Domning, 2005). This subspecies was ultimately supplanted by today’s Florida manatees.

This evolutionary framework is further validated by genetic evidence. Studies illustrate that Florida manatees trace their ancestral lineage back to Caribbean forebears that migrated northward during the past 12,000 years (Garcia-Rodriguez et al., 1998). A 2012 study by Tucker et al. supports this theory, revealing greater genetic diversity in manatees located on Florida’s western coast compared to those on the eastern side. Over time, primary populations trekked northward, with some groups heading south and east along the Florida shoreline before proceeding northward along the Atlantic. This migratory trend resulted in a west coast population with increased genetic variety, while the east coast group harbored only a limited genetic subset. These findings imply that the founding group of Florida manatees—arriving around 12,000 years ago—stemmed from Florida’s southwestern shores, which evolved into the hub of the state’s manatee populace (Reep and Bonde, 2006). The concept of vicariance further reinforces this perspective; as geographical and ecological obstacles emerged, they likely segregated the Florida manatee populations from their Caribbean forebears. Such isolation probably restricted migration between the areas, enabling the formation of local populations in southwestern Florida.

Manatees not only embody a valued emblem of Florida’s natural heritage but also represent a species with profound evolutionary and historical connections to the region. In conclusion, despite recent assertions challenging their indigeneity, extensive fossil and genetic evidence substantiates that manatees have occupied Florida’s waters for millennia, with ancestors dating back more than 12,000 years. We concur with the authors of the published material that safeguarding these iconic species and their habitats is crucial for maintaining Florida’s distinctive ecological identity for generations to come.

###

Beth Brady is the Senior Science and Conservation Associate at Save the Manatee Club, with a focus on manatee biology and conservation. She holds a Ph.D. from Florida Atlantic University and a Master’s in Marine Science from Nova Southeastern University.

References

Domning, D. P. (1982). Evolution of manatees: a speculative history. Journal of Paleontology, 599-619.

Domning, D. P. (2005). Fossil Sirenia of the West Atlantic and Caribbean region. VII. Pleistocene Trichechus manatus Linnaeus, 1758. Journal of Vertebrate Paleontology, 25(3), 685-701.

Garcia‐Rodriguez, A. I., Bowen, B. W., Domning, D., MIGNUCCI‐GIANNONI, A. A., Marmontel, M., Montoya‐Ospina, R. A., … & McGuire, P. M. (1998). Phylogeography of the West Indian manatee (Trichechus manatus): how many populations and how many taxa?. Molecular Ecology, 7(9), 1137-1149.

Marsh, H. (Ed.). (2022). Ethology and behavioral ecology of Sirenia. Cham: Springer.

Reep, R. L., & Bonde, R. K. (2021). The Florida manatee: biology and conservation. University Press of Florida.

Rycyk, A. M., Factheu, C., Ramos, E. A., Brady, B. A., Kikuchi, M., Nations, H. F., … & Takoukam Kamla, A. (2021). First characterization of vocalizations and passive acoustic monitoring of the vulnerable African manatee (Trichechus senegalensis). The Journal of the Acoustical Society of America, 150(4), 3028-3037.

Tucker, K. P., Hunter, M. E., Bonde, R. K., Austin, J. D., Clark, A. M., Beck, C. A., … & Oli, M. K. (2012). Low genetic diversity and minimal population substructure in the endangered Florida manatee: implications for conservation. Journal of Mammalogy, 93(6), 1504-1511.