Researchers want to involve the diving community in tracking the movements of one of the most docile sharks in Hawaiian waters, the whitetip reef shark.

Scuba divers and free divers occasionally come across the animals in caves and other sheltered locations. They feed at night and normally rest during daylight hours.

University of Hawai'i zoologist Nick Whitney, who works at the Hawai'i Institute of Marine Biology, said people often see a whitetip in the same cave over a long period of time and assume it's always the same shark.

"We're finding it's not," he said.

Whitetips appear to remain in one region for a few days or weeks and then move on, sometimes miles away, and they may stay away for weeks or months. The animals have been recorded moving as much as five miles up or down the coast in a few days. They have not been confirmed to travel interisland, but Whitney said he expects to find such cases as the program progresses.

Whitney is leading a research program to try to find out just how frequently the sharks are on the move, where they go and how often they come back. To do so, he has been photographing sharks and is asking members of the diving community to send in their own photos of whitetip reef sharks.

In addition to the characteristic white tips on the upper edges of their dorsal and tail fins, they also have black spots on their sides. Those spots differ with each shark and can be used like fingerprints to distinguish one from another.

"As long as we have a good photo, it's pretty easy to tell them apart" from the dot patterns, he said.

People who send photos should include the date and location the shots were taken.

"We're trying to get photos from as many people as possible around the Islands in order to track their movements and residence times," Whitney said.

He hopes to develop a library of shark photos and to find the same sharks photographed at different times and in different places.

Whitetips feed on fish, eels, octopus, crabs and other marine life. They occasionally will take a fish that has been speared or hooked by fishermen and divers. Whitney said it is not unusual to see hooks in their mouths.

It is normally safe to swim by them, but not to touch them.

"In general, they are pretty docile — so docile that some people grab them and that's when you can get bit," Whitney said. "They don't like to get harassed."

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.