About This Project

The Florida manatee is a coastal marine mammal, endemic to the southeastern US. It is listed as an endangered species by federal and state agencies, and the subject of active conservation efforts. Despite ongoing conservation concern, no reliable estimates of population size exist for any region of the species’ range. We aim to estimate manatee abundance, group size, and detection probability using repeated helicopter surveys, corrected by statistical models to account for imperfect detection.

Ask the Scientists

What is the context of this research?

The Florida manatee is a coastal marine mammal, a subspecies of the West Indian manatee endemic to the southeastern United States. It is currently listed as an endangered species by federal and state agencies, and hence is the subject of active conservation in this region. The species faces a number of threats, including entanglement with fishing gear, loss of warm-water refugia during winter, injury by water control structures, and most acutely, collisions with watercraft. Despite ongoing conservation concern, no reliable estimates of population size exist for any region of the species’ range. The development of statistically robust estimators for the Florida manatee is seen as an important component for assessing the recovery of the species, and is an active area of current research.

What is the significance of this project?

Current practice for monitoring the manatee population uses uncorrected counts taken during simultaneous large-scale aerial surveys in winter. These synoptic surveys are restricted to a small number of sites at which animals are known to aggregate during cold periods. The issues with using simple counts as an estimate of population size are well-documented, and preclude their continued use as a monitoring tool. Primary among these issues is that counts of marine mammals are biased by incomplete and heterogeneous detection. Incomplete detection can occur when observers fail to perceive animals, or when animals are subsurface and unavailable to be observed. Heterogeneity in detection may create the illusion of population trends where none actually exist or mask actual population trends.

What are the goals of the project?

1. Estimate inter- and intra-annual manatee abundance

2. Estimate group size

3. Estimate detection probability

4. Assess whether opportunistic sightings correlate with estimated abundance of surrounding waters.