West Indian manatee movements reveal novel occupancy and distribution patterns in the northern Gulf of Mexico

Since the 1980s, West Indian manatees (Trichechus manatus) have been reported more frequently along the northern Gulf of Mexico (GOM) coast in areas that were recently considered to be outside the species' normal areas of occupancy. The ecological importance of the northern GOM region to manatees is currently unclear, but knowledge of the spatial ecology, population linkages, and habitat associations of individuals occupying the fringes of their known range is vital to bring context and improve understanding of demographic trends and potential threats to the species, rangewide. We tracked regional-scale movements of 13 manatees documented in Mobile Bay, AL using satellite telemetry and mark-recapture methods. We determined movement and occupancy patterns including origins, seasonal dispersal and site fidelity, and functional movement modes of those individuals during the tracking period. Focal manatees moved along the GOM coast between Tampa Bay, FL and Lake Pontchartrain, LA, and consistently returned to discrete locations in both the northern GOM and within the species' core range in peninsular FL. Functional movement model fits confirmed that most relatively long-range seasonal movements were migratory in nature, suggesting that consistently occupied migratory endpoints contain relatively important seasonal habitat for manatees and diminishing the possibility that tracked manatees were nomads or transient within the study area. These results provide evidence of shifting seasonal manatee distribution in the US, and highlight repeatedly used locations that may increase in importance to the species if manatee abundance in the northern GOM increases.