Project Methods

ARGOS Satellite Tracking

The project goal is to follow West Indian manatees living in Belize by satellite tracking them using the ARGOS system. Service ARGOS is a cooperative venture under the joint management of France's Center of National Space Studies and the United States of America's National Oceanic and Atmospheric Administration (NOAA) and its National Aeronautics and Space Administration (NASA). The purpose of ARGOS is to allow citizens to remotely collect environmental data on a wide range of subjects, including: meteorology, oceanography, and animal ecology.

To track each manatee a special transmitter placed in a waterproof container is attached by a four-foot tether to the manatee's tail. The towed transmitter broadcasts to a receiver placed on low-flying (525 miles altitude), polar orbiting Tiros-N satellites (currently NOAA-D, J, H, K and L). A computer on the satellite records signals from the transmitters during each overpass. The satellite, in turn, relays the manatee data to Earth-based listening stations where ARGOS computers determine the location of the manatee. Finally, the locations are sent to the project scientists via the Internet. The locations of the manatees are accurate to about 0.6 mile.

In addition to location information, the manatee transmitters also record, and relay to the scientists via the ARGOS satellite link, information concerning the manatees' diving behavior (dive number and dive duration), local water temperature, and the transmitter's battery status.

Satellite overpasses occur in Belize about 12 times per day, each pass lasting about 12 to 15 minutes. In order to conserve transmitter batteries , some transmitters are programmed to broadcast only eight hours per day, and others broadcast for eight hours every other day. As a result, two to five locations are received per broadcast day. Each day the scientists enter the data sent to them by ARGOS into a computer database and prepare animal tracking maps.

Attachment of Satellite Transmitters

The radio tracking component of the project was initiated in November 1997 with the tagging of two manatees  and has continued to the present.  Each tagging required temporarily capturing the manatee with the method described below.

The captures have taken place in the Southern and Quashie Trap lagoons located about 20 miles south of Belize City, near the village of Gales Point, see (Belize Reference Map).. For the capture, the team, working in a small boat, first find a manatee and then slowly encircled it with a net.
The team guides the netted manatee to shore by slowly towing it from the boat into shallow water, and eventually onto a beach. In the hands of skilled wildlife biologists, beached manatees will remain calm and can be kept safely out of the water for a short period. Scientific measurements of the manatee are taken, and then the waterproof canister is attached to the tail of the manatee by a four-foot tether. The tether is specially designed to break if it becomes entangled in vegetation or debris. Once outfitted the manatee is returned to the water and released.

Manatees remain submerged except when they briefly surface for air, and on rare occasions they stick their head and shoulders out of the water when feeding. However, it is not uncommon for them to be within six feet of the surface, and since it is necessary for the radio's antenna to be out of the water when transmitting, the transmitter's canister is designed to be buoyant with the antenna sticking above the water surface whenever the manatee is within six feet of the surface. The photo shown here ( courtesy Sirenia Project) depicts how the transmitter's antenna protrudes when the tagged manatee travels or floats near the water surface.

Summary data maps for tagged animals are available in Data Maps