Tracking animal migration

For years scientists have been tracking animals and the ways they migrate. Many have done this for research, some have done this to help animals and monitor them.

Technologies for tracking
In the fall of 1803, American Naturalist John James Audubon wondered whether migrating birds returned to the same place each year. So he tied a string around the leg of a bird before it flew south. The following spring, Audubon saw the bird had indeed come back.

Scientists today still attach tags, such as metal bands, to track movement of animals. But metal bands are not always useful tags. That is because the tagged animals have to be caught again for the scientists to get any data. Unfortunately, most tagged animals are never seen again.

Recent technologies have helped solve this problem. Electronic tags give off repeating signals that are picked up by radio devices or satellites. Scientists can track the locations and movement of the tagged animals without recapturing them. These electronic tags can provide a great deal of data. However, they are more expensive than the low-tech tags that aren't electronic. Also, because of their weight, electronic tags may harm some animals by slowing them down.

Radio tracking
Tracking an animal by radio invovles two devices. A transmitter attached to the animals sends out a signal in the form of radio waves, just as a radio station does. A scientist might place the transmitter around an animals ankle, neck, wing, or fin. A receiver picks up the signal, just like your radio at home picks up a stations signal. The receiver is usuallly in a truck or an airplane. To keep track of the signal, the scientist follows the animal in the truck or plane.

Satellite tracking
Receivers can be place in placed in Earth-orbiting satellites as well as in airplanes and trucks. Networks, or groups, of satellites are used to track animals. Each satellite in a network picks up electronic signals from a transmitter on an animal. Together, the signals from all satellites determine the precise location of the animal. The satellites also track the animal's path as it moves. Satellite tracking is especially useful because the scientists do not have to follow after the animal. Instead, the satellites move. Satellite networks have tracked the migration of caribou, sea turtles, whales, seals, elephants,bald eagles, and ospreys.

Why tracking is important
Electronic tracking tags are giving scientists a complete, accurate picture of migration patterns. For example, when scientists used radio transmitters to track one herd of caribou, they learned two important things. First, they learned that the herd moves previously thought. Second, they learned that each year the herd returns to about the same place to give birth to its young. This information would have been difficult to obtain with "low tech" tags.


 * Tracking migrations is an important tool to better understand and protect species. For example, Florida manatees are an endangered species, and therefore they need protection. Radio tracking showed that Florida manatees may travel as far as Rhode Island when they migrate. This information suggests that the manatees may need protection along much of the Atlantic Coast of the United States. Previously, protection efforts focused mainly in the Florida area.


 * Technologies for tracking animals may also help people whose work or recreation affects animals. For example, suppose officials at a state park want to protect a group of migrating animals during the spring. The officials plan to ban fishing or boating for the spring season. Detailed migration information, however, might give the officials a better choice. They might be able to decrease the length of time the ban is in effect, or ban fishing and boating only in those few areas visited by animals.