Historic accounts reveal manatee populations increased in the 1800s and 1900s alongside human populations

Florida manatees are threatened by human activity, but they're also doing better than ever, according to a study examining manatee populations since 12,000 BC, published November 20, 2024 in the open-access journal PLOS ONE by Thomas J. Pluckhahn of the University of South Florida and David K. Thulman of George Washington University, Washington DC, U.S.

Florida manatees are an iconic species and also a conservation concern, threatened by environmental change and watercraft collisions. Historical manatee populations are poorly understood, and therefore little is known about the state of manatees before modern human influence, making it difficult for conservationists to set goals for establishing healthy manatee populations.

In this study, the authors investigate manatee populations between 12,000 BC and the mid-20th century by compiling records of manatee remains from archaeological sites as well as historical accounts of manatee sightings from newspapers, journals, and other sources. The data indicates that manatees were quite rare during most of this time period before increasing in population size and distribution during the 1800s and 1900s, coincident with increasing human populations. This population growth is likely related to expanded conservation laws, improved public perception of manatees, and warming water temperatures due to climate change and power plant construction.

Despite their modern reputation as a rare species, these results suggest that Florida manatees are more abundant today than any previous time in North American human history. Many of the anthropogenic changes that endanger the species today are also likely responsible for their population growth over the past two centuries. The authors note that manatee conservation goals cannot simply aim for a return to pre-modern population conditions, and that a detailed understanding of their history and ecological relationship with humans will be necessary to establish healthy conservation goals.

The authors add: "Manatees are among Florida's most iconic species, so the possibility that they were not common here until the modern era is surprising. There is a lot of uncertainty regarding changes the Anthropocene will bring in the future, as human-caused climate change accelerates. But our study serves as a reminder that we don't even fully understand the changes that have already occurred across the modern era. We think there are lessons from that history which might be helpful for managing a better future for both people and manatees in Florida."

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In your coverage please use this URL to provide access to the freely available article in PLOS ONE: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0313070

Citation: Pluckhahn TJ, Thulman DK (2024) Historical ecology reveals the "surprising" direction and extent of shifting baselines for the Florida manatee (Trichechus manatus latirostis). PLoS ONE 19(11): e0313070. https://doi.org/10.1371/journal.pone.0313070