Manatee Distribution and Habitat Use in the Northern Gulf of Mexico

Science Center Objects

USGS works with partners to assess manatee distribution and habitat use throughout the Northern Gulf of Mexico.

Northern Gulf of Mexico Manatee GPS distribution map
Northern Gulf of Mexico Manatee GPS distribution map

The Science Issue and Relevance: Florida manatees range along the Gulf of Mexico coast from Florida to Texas, although little is known about manatee use areas and habits west of the Suwannee River. Along with a documented increase in the Crystal River subpopulation, winter use at alternate natural springs in northwestern Florida is increasing. Several warm water refuges in this region are the focus of a USGS integrated study on manatee carrying capacity of northwestern Florida springs, for which detailed data on manatee use are needed. Also, agency interests in the distribution and movement patterns of manatees along the northern Gulf of Mexico (NGOM) increased dramatically following the Deepwater Horizon oil spill in FY11. Trends in sighting data suggest recent increases in use by manatees of near-shore coastal areas of western Florida, Alabama, Mississippi, Louisiana, and Texas. The U.S. Fish and Wildlife Service (USFWS) Manatee Recovery Plan and 5-year Status Review for the West Indian Manatee both identify natural springs in northern Florida as important winter habitat for manatees and recommend protection measures to ensure their future availability to manatees. Research on manatee resource use along the northwestern range will address informational needs necessary for effective management actions.

Methodology for Addressing the Issue: The area of interest for this study extends from the Suwannee River, Florida, west along the Gulf coast through Texas. Manatee distribution and habitat will be assessed through several research actions involving multiple agencies and partners. Reporting of manatee sightings from this area are compiled in a central database through coordination with local, state, and federal partners. Photo identification field efforts are enhanced through site visits by staff to selected aggregation sites, and through coordinated participation with partners. Tissue sampling of individual manatees for USGS genetic-based studies is being coordinated under USFWS permit. Radio tracking studies are conducted to determine local and regional movement and habitat use patterns. Identification of specific manatee resources will be accomplished through the use of remotely-monitored GPS tracking devices and field observations. Salinity and temperature loggers will be deployed on tagged individuals and at key sites within use areas to typify variations in timing and spatial extent of freshwater and warm-water resources. Tracking and field data are analyzed for specific resource use patterns, including identification and characterization of overwintering, foraging, and freshwater access sites, and statistics are applied to address trends in manatee abundance and distribution within discrete habitat/study units. The discerned patterns of zonal use determined through analyses of radio tracking data are valuable to parameterize models for statistically-sound aerial surveys for trends in distribution. Activities are conducted in accordance with USFWS permit issued to the USGS/Sirenia Project and comply with USGS/SESC IACUC standards.

Photo identification of manatees
Photo identification of manatees

Future Steps: This research initiative is projected as the start for an extended study on NGOM manatee distribution and use patterns, and characterization of local resources. The extent of field efforts will be developed on a regional basis, targeting areas with appropriate habitat or consistent manatee use, coupled with interest and participation among cooperating agencies. Specific areas for manatee radio tagging are based on field monitoring logistics and federal or state management needs. Based on cooperative interactions with agencies addressing the BP oil spill, there is increasing interest within DOI for understanding the relationship of manatee distribution and habitat use to NGOM oil exploration activities.

Related project(s) or product(s): Activities employs established sampling protocols used by USGS for manatee genetic and photo-identification studies in direct support of a USGS integrated studies on manatee health, contaminants and population genetics. These activities are in direct support of a USGS integrated study on the carrying capacity of northwestern Florida springs used by manatees.