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The Bounty: A close-up of the versatile, delicious, generous and soon-to-be-ubiquitous breadfruit.
Vol.12, No. 4
August/September 2009

  >>   Across the Great Divide
  >>   Tree of Plenty

The Way of the Whitetip 

story by Sheila Sarhangi

Studying wild sharks can be difficult. Either they’re large and dangerous to handle, or they range. White-tip reef sharks aren’t dangerous, but they are elusive. They’re not only rare in the main Hawaiian Islands, they’re careful feeders, slow to take a baited hook. So, up until six years ago, almost no one had studied their movements. Questions as simple as “Do they live in the same area their entire lives?” went unanswered.

Nick Whitney, a then-grad student at the University of Hawai‘i at Manoa, wanted to answer them. But the usual approach—tagging the sharks with tracking technology—proved ineffective because white-tips are both cagey and rare. Instead, he created an innovative and inexpensive research design that created a much larger data pool than trackers would have availed: He handed out fliers to dive shops, underwater photography clubs and hotels, asking sport divers to snap photos of the sharks, record their location and submit them via Internet. Because each white-tip has a unique pattern of spots on its sides, Whitney can identify individual sharks from a snapshot. And they’re easy to photo-graph; white-tips are lazy, indolent even. They spend most of the day hanging out in caves or lying under coral ledges (they’re one of the few species of shark that can breathe by pumping water over their gills, whereas other sharks must swim or they suffocate).

After six years and roughly 1,500 images from more than 100 photographers, it turns out that white-tips aren’t slackers at all; they roam much farther than anyone thought. “We had several animals that moved back and forth over a distance of 10 kilometers or more,” explains Whitney. “The longest movement was a female who traveled 24 kilometers. She was first seen as a juvenile on the east side of Waimanalo, and then we didn’t see her until four years later, when she was a full-grown adult off of Waikiki.” Deep water doesn’t intimidate them, either. Two sharks crossed a 400-foot-deep channel separating Molokini Crater from South Maui. As a bonus, Whitney also discovered that females could give birth every year, not just every two years as previously thought. How could he tell? When pregnant, white-tips look like blimps with fins.

Whitney is still accepting photos through his web site. Within the next year, the results will be published in a scientific journal. HH