Marine scientists in Hawaii are equipping Hawaiian monk seals with a cell phone-like device to track where the seals have been and what they have been doing.

National Oceanic and Atmospheric Administration scientists are trying to find out why the population of the endangered seals is growing around the main Hawaiian Islands but declining in the Northwest Hawaiian Islands.

Charles Littnan, lead scientist for NOAA's Hawaiian Monk Seal Research Program, said while scientists have used satellite GPS tags to track seals before, those tags were limited by the amount of information they could send via satellite.

The new device, about 3 inches long and worth about $4,000, is glued to the animal's back and sends messages back to scientists via cell phone towers.

The tag is like a “;smart phone”; that can record a location every time the animal surfaces and environmental data such as water pressure, depth, temperature and salinity.

It sends a text message to scientists with the data, which can be configured into maps of the animals' behavior.

Littnan said if the cell phone tags work successfully around the main islands, the scientists will explore using portable cell phone towers in the more remote northwest islands. Experts have previously collected data on Northwest Hawaiian Island monk seals using “;critter cams,”; or small cameras glued onto the animals' backs.

That data will be compared with the information from cell phone tags to learn what might be going wrong for the seals in the northwest islands.

Already, the new devices are showing that monk seals in the remote islands travel farther and dive deeper for food than seals in the main islands.

Seals around the populated islands dive less than a quarter-mile and forage for food for only several hours. Seals in the Northwest Hawaiian Islands, however, dive about a mile down and stay in the ocean for up to two weeks looking for food.

Littnan suspects Northwest Hawaiian Island seals might be struggling to survive because they are also competing with sharks and ulua that are much larger than in the main islands.

The project could also provide additional answers about monk seal behavior, such as how many seals the main islands can support, how much competition they are to fishermen, and their feeding habitats.

About 15 to 20 animals are expected to be tagged. While four already have been tagged, only two tags are transmitting data. The experts will remove the tags in about six months before the seals molt or the tags fall off.

The $150,000, one-year project is a joint effort by NOAA and the Navy, which wants to find out whether sonar use is affecting monk seal behavior.