Researchers Develop Aid to Study Human-Dolphin Interaction

Scientists have long believed tourists intent on getting close to spinner dolphins may be disturbing their critical rest period.

Now researchers at Duke and Stony Brook universities say they have developed a new tool that will help identify areas where such problems occur.

Mapping models developed by scientists at Duke’s Nicholas School of the Environment show that only a fraction – 21 out of 99 – of the bays in a study area on the leeward coasts of the main Hawaiian islands were suitable habitats for resting dolphins.

That means that conservation efforts can be focused on specific areas, rather than limiting access to large areas, said Lesley Thorne of Stony Brook, lead author of the study published Friday in the on-line peer-reviewed journal PLOS ONE.

“It would be next to impossible to survey spinner populations and human activities in every bay that might be a resting habitat,” Thorne said in a statement issued by Duke University. “We’re talking about hundreds of bays in the Hawaiian islands alone.”

While scientists and conservationists have long worried that the growing number of interactions between the dolphins and tourists may be placing the spinners at risk, there have been few published studies on the subject.

“Sleep is critical for most animals,” said David Johnston, one of the study’s authors. “When deprived of their necessary ‘zzzz’s,’ they gradually show a decreased ability to process information and remain attentive to environmental stimuli.”

The study’s authors included Adam A. Pack, an associate professor of psychology at the University of Hawai`i at Hilo. Pack could not immediately be reached for comment.

Researchers created the maps by studying such factors as water depth, size and proportion of the bays, and proximity to deep-water foraging grounds. The study involved hundreds of spinner dolphin sightings made between 2000 and 2010.

The scientists had to distinguish between dolphins who were resting and those who were active, when they are more tolerant of the presence of humans.

Repeatedly depriving dolphins of rest leaves them less able to forage for food or detect the presence of nearby predators, the researchers said. Their ability to produce sounds used for communication and navigation may also be impaired.

The researchers plan to test their modeling techniques in the Northwestern Hawaiian Islands and elsewhere in the Pacific.