Satellite Tags to Solve Hammerhead Mating, Migration Mysteries?

Adrianne Appel
for National Geographic News
February 1, 2006

How far would you go to save a species? When it comes to great hammerhead sharks, Wes Pratt shows more mettle than most.

In a few weeks, the marine scientist will attach satellite-tracking tags—by hand—to two of the 500-pound (230-kilogram), 12-foot (3.7-meter) predators as they feed off the Bahamian coast.

Pratt, a biologist at the Mote Marine Laboratory Center for Shark Research, in Summerland Key, Florida, hopes the tracking data can help garner protections in the Bahamas for the rare species.

"We need to establish their activity patterns and where their nursery is," he said, adding that he also hopes to learn whether the sharks have a mating season.

Pratt and his colleagues will conduct underwater observations and record video of the sharks during their field research, which is funded in part by the National Geographic Society's Expeditions Council.

Limited Protection

Named for its large size and the hammer-like shape of its head, the great hammerhead (Sphyrna mokarran) is one of nine hammerhead shark species.

Why the sharks developed such an odd head shape isn't known. But it does create a larger surface area for special sensory organs embedded in their skin.

Sharks rely on the pore-like electrical sensors, known as ampullae of Lorenzini, to pinpoint their prey at ultra-close range.

That prey includes stingrays, which the sharks hunt in subtropical coastal and deep ocean waters.

The great hammerhead is somewhat protected while it swims in United States coastal waters, where commercial fishing of large sharks is allowed but restricted.

A number of other nations also protect the species. But most do not, and the great hammerhead is not protected when in international waters.

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