Population Ecology of Florida Manatees

Science Center Objects

USGS is working with partners to understand how the federally protected Florida manatee population changes over time and responds to threats.

Manatee and calf

Manatee and calf (Public domain.)

The Science Issue and Relevance: Understanding how the federally threatened Florida manatee population changes over time and responds to threats is important for managers of state and federal management agencies, particularly U.S. Fish and Wildlife Service (USFWS) and the Florida Fish and Wildlife Conservation Commission (FWC). 


West Indian Manatee Population Genetics

West Indian manatees congregate around a warm-water source in Florida. (Public Domain)

Methodology for Addressing the Issue: We have developed several estimators of abundance that use aerial count data from aircraft and unmanned aerial systems surveys and account for observation errors during surveys. USGS Patuxent (in collaboration with USGS WARC, Florida Fish and Wildlife Conservation Commission (FWC), and US Fish and Wildlife Service (USFWS)) is leading the development of a population projection model, the Core Biological Model (CBM), which was developed to project manatee abundance, the probability of quasi extinction, and evaluate threats in the long term (e.g., 60 years). It is an important tool for managers to assess the status of the manatee population and major threats. However, this model was not designed to quantify the effect of specific events (e.g., red tide event of 2013 or cold mortality events of 2010), it is also not suited to make inference about historic trends. Therefore, we are working on developing an integrated population model (IPM) that would provide critical information that is complementary to the CBM. This IPM model is led by FWC (in collaboration with USGS WARC and USGS Patuxent).


Future Steps:

The IPM model would allow managers to (1) better understand the impact of specific events on the population; (2) track historical changes in the population; (3) set up a framework to increase accuracy and precision of key parameters used in the CBM; (4) evaluate scientific hypotheses relevant to the population dynamics of manatees; and (5) could ultimately help with the prioritization of monitoring information (e.g., establish frequency and intensity of monitoring).


Related Products: 

Martin, J., Royle, J. A., MacKenzie, D.I., H. H. Edwards, M. Kery, Gardner, B. (2011) Accounting for non- independent detection when estimating abundance of organisms with a hierarchical Bayesian approach. Methods in Ecology and Evolution, 2, 595–601.


Dorazio, R.M., Martin, J., Edwards, H.H. (2013) Estimating abundance while accounting for rarity, correlated behavior, and other sources of variation in counts. Ecology, 94, 1472-1478.


Martin, J., Edwards, H.H., Bled, F., Fonnesbeck, C.J., Dupuis, J.A., Gardner, B. (2014) Estimating upper bounds for occupancy and number of manatees in areas potentially affected by oil from the Deepwater Horizon oil spill. PLoS ONE 9, e91683.


Martin, J., Edwards, H.H., Fonnesbeck, C.J., Koslovsky, S.M., Harmak, C, Dane, T. (2015). Combining information for monitoring at large spatial scales: first statewide abundance estimate of the Florida manatee. Biological Conservation, 186, 44-51.


Martin, Julien, Runge, M.C., Flewelling, L.J., Deutsch, C.J., and Landsberg, J.H., 2017, An expert elicitation process to project the frequency and magnitude of Florida manatee mortality events caused by red tide (Karenia brevis): U.S. Geological Survey Open-File Report 2017–1132, 17 p., https://doi.org/10.3133/ofr20171132.


Runge, M.C., Sanders-Reed, C.A., Langtimm, C.A., Hostetler, J.A., Martin, J., Deutsch, C.J., Ward-Geiger, L.I., and Mahon, G.L., 2017, Status and threats analysis for the Florida manatee (Trichechus manatus latirostris), 2016: U.S. Geological Survey Scientific Investigation Report 2017–5030, 40 p., https://doi.org/10.3133/sir20175030.


Hostetler, J. A., Edwards, H. H., Martin, J., and Schueller, P. 2018. Updated Statewide Abundance Estimates for the Florida Manatee. Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute Technical Report No. 23.