Updated FWC Monitoring Strategy for Florida Manatee Carcasses

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. The FWC Wildlife Alert Hotline 1-888-404-FWCC (1-888-404-3922) provides 24/7 communication support regarding public reports of manatee carcasses and live manatees in distress. All reported manatee carcasses, regardless of salvage or disposition, are documented in the manatee mortality database after verification by FWC manatee biologists. Through all of these important efforts, the FWC contributes significantly to the evaluation of threats facing Florida manatees and provides key information to resource managers and partner agencies.

Salvage and necropsy of large carcasses can be a time-consuming and expensive process, which involves fielding reports from citizens, using specialized equipment to secure and transport carcasses, conducting the necropsies, collecting and processing samples, managing data and information, and properly disposing remains. Manatee carcass numbers have increased over time (with added peaks during Unusual Mortality Events or ‘UME’s). For example, the overall number of manatee carcasses documented statewide increased from 272 in 2000 to over 1,000 in 2021.  It is no longer feasible nor necessary to necropsy nearly every carcass reported in Florida; however, a strategy is needed to meet essential conservation information needs.

In light of high and increasing annual carcass loads,  FWC sought to design and implement an objective-driven carcass response and necropsy program that adequately informs conservation managers about threats to the Florida manatee while strategically focusing staff effort.  To this end, FWC conducted a workshop with conservation experts to help evaluate strategies and consider ways to streamline work. In February 2021, the FWC implemented newly developed protocols for manatee carcass recovery and case selection for necropsy. The adoption of these protocols also resulted in greater time and resources to focus on the highest priority cases such as emerging health concerns or unusual mortality investigations.

To meet essential information needs, full necropsy examinations are performed under a surveillance protocol (see 1. below) to track key threats.  Additionally, certain carcasses are selected to address other priority objectives that require detailed necropsies and to support health investigations.  Under the current protocols, manatee carcasses are sampled for one or more of 4 general purposes:

1. For perpetual cause of death surveillance, a stratified random sampling approach is used. For each of the 5 FWC regions across the state (Fig. 1.), the first intact, non-perinatal (non-newborn) carcass reported during a 10-day period is recovered and necropsied. Using this approach, data will be acquired to estimate fractions or patterns of mortality from various causes.
2. Additional carcasses are selected for necropsy to support focused investigations of manatee health, unusual mortality, human-related threats (such as entanglement in marine debris and entrapment in water-control structures), environmental concerns of public interest (such as oil spills and harmful algal blooms), and manatee rehabilitation outcomes.
3. Carcasses that do not fall into either of the above 2 categories are not necropsied; however, depending on level of decomposition and other factors, external carcass information may be acquired through a field response overseen by FWC. In addition to location and date, external carcass information such as length, sex, genetic samples, and photographs are collected and sometimes a partial necropsy is conducted. These carcasses are listed as ‘Verified; Not Necropsied’ in the manatee mortality database and information is used in population models.
4. In all other cases, the carcass report is verified through photographs, and the location and report date are recorded, but there is no field response. As in 3), these carcasses are listed as ‘Verified; Not Necropsied’. These data are also included in statewide carcass counts and population models.

In addition to FWC sampling protocols, concerns for staff safety or logistical constraints (such as major storms) may prevent a field response to a manatee carcass; nonetheless, typical verification steps will be implemented.

This sampling approach will provide critical data about the prevailing threats to manatees across the state, even though some information will be lost by not necropsying all carcasses. Additionally, the location and number of documented deaths, even in the absence of cause of death information, will be used to better understand manatee population dynamics.