The scientists are part of the Sirenia Project, named for the scientific order that includes manatees and dugongs, also known as sea cows. They conduct long-term, detailed studies on the life history, population dynamics, and ecological requirements of the endangered Florida manatee (Trichechus manatus). Project biologist Cathy Beck has played a key role in providing manatee data to the Journey North Web site.
Journey North is used in more than 9,000 schools in North America as a model for improving math and science education for K-12 students. It is supported by the Annenberg Foundation and the Corporation for Public Broadcasting. Through Journey North, students participate in tracking the migration of monarch butterflies, hummingbirds, manatees, and other mammals, the budding of plants, and changes in the local environment, all via the Internet. For the past 6 years, the USGS' Sirenia Project has participated by providing data on movements of individual radio-tagged manatees. The project also provides photographs and biological information on the species.
Each week, coordinates of selected radio-tagged manatees are submitted to Journey North for posting on the Web site. Students can then plot new manatee locations, answer questions about where the animals have moved, and hypothesize about why certain animals have or have not moved. The students are also provided with life-history information about the manatees; for example, they are told when a calf is born to one of the tagged manatees and how the birth might affect her movement patterns. The students are learning how to locate sites on a map by using latitude and longitude, how to read depth contours, and how to relate an animal's response to weather patterns, food resources, changes in freshwater availability, and other factors. The feedback the USGS receives from teachers and students demonstrates how much thought and discussion ensue in the classroom!
The Web site is a great resource for educators, as well as for parents with children especially interested in animals and migratory behavior. The site is active from January through April. Archives of data, maps, photos, and related materials remain on the site year-round.
How Manatees Are Tagged for Radio Tracking
To capture manatees for tagging, USGS scientists use a net deployed from shore or a boat. For shore-based captures, nets are partially set at a selected site where a manatee is expected to appear. The depth of the net must exceed the depth of the water, and leadlines are onshore. Thus, a partial bag is really what is in the water, with a line on the floatlines so that the crew can pull it in when the "right" manatee swims into the "bag." For an adult manatee, a strong, experienced crew of 8 to 10 people or more, waiting quietly on shore, is needed. Boat captures are preferred for recapturing tagged manatees (for medical assessment, for example), for capturing injured manatees, and for capturing manatees in areas without an adjacent smooth beach for safely hauling the manatee ashore. For boat captures, the chosen manatee is spotted, and a net is carefully set around it, then pulled. The capture boat has an open stern that allows the boat crew to pull the net and manatee directly on board. The stern actually sinks a bit, soaking the crew, as the manatee is pulled aboard. Because there is less working room on board the boat than on the shore, boat captures require the strongest members of the capture crew. When a manatee is captured by either method, every member of the capture team has a job. The goal is to assess, tag, and release as quickly as possible.
The tag assembly consists of a buoyant cylinder (seen floating behind the manatees in the photograph) containing a very high frequency (VHF) radio-wave transmitter that allows researchers to locate the manatees while in the field. Enclosed in the tag housing is an ultra-high-frequency (UHF) transmitter, also referred to as a platform transmitter terminal, or PTT. The PTT allows the manatees to be tracked remotely by the Service Argos monitored satellite system. A few of the tags also include a global-positioning-system (GPS) data logger.
The cylinder is connected to a flexible tether attached to a padded belt that fits around the base of the manatee's tail. A sonic beacon is built into the belt to enable manatees that have lost the transmitter to be relocated and identified. The "life" of the tag depends on many factors. Battery life is about 2 years for the VHF transmitter and about 6 months for the PTT. The tether has a built-in weak link designed to break free from the manatee if the tag becomes entangled (in mangrove roots, for example, or under dock pilings). Corrodible connections of nuts and bolts are purposely used in the belt to allow it to eventually fall off in the event it cannot be removed manually from the manatee. Tags are constructed in the USGS' Gainesville office. The development of the tag design and technical and practical improvements made over the years can be credited to Jim Reid, a biologist with the Sirenia Project.
in this issue:
Track Florida's Manatees Via Web Site