USGS is working with partners to understand how the federally protected Florida manatee (Trichechus manatus latirostris) population changes over time and responds to threats.
What is the issue?
Florida manatees were first protected through Florida State Law in 1893 and were federally protected as an endangered species starting in 1973. Today, manatees are protected by the Florida Manatee Sanctuary Act, the Marine Mammal Protection Act, and the Endangered Species Act. Progress on population recovery efforts allowed manatees to be reclassified from an endangered to a threatened species under the federal Endangered Species Act in May 2017, but additional research is needed to support continued recovery efforts and work towards the ultimate goal of delisting this iconic species.
What is at stake?
Understanding how the federally threatened Florida manatee population changes over time and responds to threats is important for managers of state and federal natural resource agencies, particularly the U.S. Fish and Wildlife Service (USFWS) and the Florida Fish and Wildlife Conservation Commission (FWC). Without a better understanding of the status of, and greatest threats to, the Florida manatee population, managers who are leading manatee recovery efforts risk spending resources on inefficient or ineffective activities.
What is our approach?
Our approach focuses on three types of quantitative tools.
- Survey methods to estimate abundance
The USGS and partners have developed methods to estimate abundance using aerial count data from aircraft and unmanned aerial systems surveys that account for observation errors during surveys.
- Integrated population models to estimate and understand historical patterns from multiple data sets
The USGS and partners have developed integrated population models (IPM) to provide critical information about historic trends and to quantify the effects of specific events (e.g., the red tide event of 2013 and cold-related mortality events of 2010). The first iteration of the manatee IPM was released in 2021 and reconstructed manatee population dynamics in the southwest region of Florida over the past 20 years, improved precision of key parameter estimates, and permitted inference on poorly known parameters. Continued improvements to the IPM model will 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 population projection models; and (4) evaluate scientific hypotheses relevant to the population dynamics of manatees. The IPM also could ultimately help with the prioritization of monitoring information (e.g., establish frequency and intensity of monitoring).
- Projection models that forecast future trends
Scientists at the USGS Eastern Ecological Science Center continue to lead the development of a population projection model in collaboration with FWC and USFWS. This population projection model, the Core Biological Model (CBM), was developed to project manatee abundance, to estimate the probability of quasi-extinction, and to evaluate threats to the Florida manatee population in the long term (50-100 years). The CBM provided key information to USFWS for its downlisting decision in 2017. A new version of the CBM is under development to understand the potential long-term impacts of the 2021-22 Unusual Mortality Event and to inform USFWS’s status assessment.
What are the benefits?
Population models for conservation are often used to (1) assess a population’s conservation status; (2) diagnose possible threats; (3) predict the effects of threats or management actions; and (4) identify the best possible actions for achieving management objectives. USGS leadership in the development population models for Florida manatees will allow state and federal managers to make better informed decisions to facilitate more cost-effective monitoring and recovery efforts.
USGS is working with partners to understand how the federally protected Florida manatee (Trichechus manatus latirostris) population changes over time and responds to threats.
What is the issue?
Florida manatees were first protected through Florida State Law in 1893 and were federally protected as an endangered species starting in 1973. Today, manatees are protected by the Florida Manatee Sanctuary Act, the Marine Mammal Protection Act, and the Endangered Species Act. Progress on population recovery efforts allowed manatees to be reclassified from an endangered to a threatened species under the federal Endangered Species Act in May 2017, but additional research is needed to support continued recovery efforts and work towards the ultimate goal of delisting this iconic species.
What is at stake?
Understanding how the federally threatened Florida manatee population changes over time and responds to threats is important for managers of state and federal natural resource agencies, particularly the U.S. Fish and Wildlife Service (USFWS) and the Florida Fish and Wildlife Conservation Commission (FWC). Without a better understanding of the status of, and greatest threats to, the Florida manatee population, managers who are leading manatee recovery efforts risk spending resources on inefficient or ineffective activities.
What is our approach?
Our approach focuses on three types of quantitative tools.
- Survey methods to estimate abundance
The USGS and partners have developed methods to estimate abundance using aerial count data from aircraft and unmanned aerial systems surveys that account for observation errors during surveys.
- Integrated population models to estimate and understand historical patterns from multiple data sets
The USGS and partners have developed integrated population models (IPM) to provide critical information about historic trends and to quantify the effects of specific events (e.g., the red tide event of 2013 and cold-related mortality events of 2010). The first iteration of the manatee IPM was released in 2021 and reconstructed manatee population dynamics in the southwest region of Florida over the past 20 years, improved precision of key parameter estimates, and permitted inference on poorly known parameters. Continued improvements to the IPM model will 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 population projection models; and (4) evaluate scientific hypotheses relevant to the population dynamics of manatees. The IPM also could ultimately help with the prioritization of monitoring information (e.g., establish frequency and intensity of monitoring).
- Projection models that forecast future trends
Scientists at the USGS Eastern Ecological Science Center continue to lead the development of a population projection model in collaboration with FWC and USFWS. This population projection model, the Core Biological Model (CBM), was developed to project manatee abundance, to estimate the probability of quasi-extinction, and to evaluate threats to the Florida manatee population in the long term (50-100 years). The CBM provided key information to USFWS for its downlisting decision in 2017. A new version of the CBM is under development to understand the potential long-term impacts of the 2021-22 Unusual Mortality Event and to inform USFWS’s status assessment.
What are the benefits?
Population models for conservation are often used to (1) assess a population’s conservation status; (2) diagnose possible threats; (3) predict the effects of threats or management actions; and (4) identify the best possible actions for achieving management objectives. USGS leadership in the development population models for Florida manatees will allow state and federal managers to make better informed decisions to facilitate more cost-effective monitoring and recovery efforts.