Manatee Responses to Approaching Boats: An Update
By Stephanie Nowacek, M.Sc., Lab Manager

Boat Collisions are responsible for more than 30% of manatee deaths.

DTag attached to a male manatee in Southern Lagoon, Belize.

Manatees were killed in record numbers by boats during 2002. The effectiveness of current mitigation strategies has not been determined as specific behavioral responses to watercraft are still largely unknown. With support from the State of Florida, our team of researchers (me, Doug Nowacek, Randy Wells) traveled to Belize in March of 2001 and March of 2002 to piggyback on a long-term manatee capture-release effort in Southern Lagoon led by Dr. James (Buddy) Powell, of Wildlife Trust. There we attached non-invasive digital acoustic recording devices (DTAGs) to existing peduncle belts on temporarily restrained manatees. The DTAGs, developed by Woods Hole Oceanographic Institution, recorded heading, depth, pitch, and roll of the manatee as well as the sounds reaching the manatee during preprogrammed times.

Despite heroic efforts by Powell in catching manatees and Mark Johnson and Alex Shorter in developing good deployment and release mechanisms for the tag and belt, our sample sizes remained small after the two years. Our successful deployments did show marked differences in behavior by the manatees during boat approaches as compared to periods when no boats were present. Changes in heading and fluke stroke (pitch) were more likely during boat approaches. Preliminary results indicate that manatees are detecting watercraft at much greater distances than previously thought.

We have high expectations that this methodology will provide conclusive data that will help management to develop better strategies for protecting this endangered species. To that end, we will continue our research by now deploying tags in Florida waters. Comparing responses of manatees in the relatively quiet waters of Belize to those of animals in the busy waters of Florida will hopefully provide information needed to reduce manatee mortality and serious injury from boat collisions.