Sep. 5, 2013 — A quarter of the mature female tiger sharks plying the waters around the remote coral atolls of the Northwestern Hawaiian Islands decamp for the populated Main Hawaiian Islands in the late summer and fall, swimming as far as 2,500 kilometers (1,500 miles) according to new research from University of Florida and the University of Hawaii. Their report is scheduled for publication in the November 2013 issue of Ecological Society of America's journal Ecology. The authors' manuscript is available as a preprint.
"When we think of animal migrations, we tend to think of all individuals in a populations getting up and leaving at the same time, but it's not as simple as that," said first author Yannis Papastamatiou of the University of Florida. "Some are resident and some are transient."
Among all migrating animals, from birds to elk to 15-ft ocean predators, some portion of the population remains behind when the rest leave on their seasonal journeys. Animals have choice. On what factors does choice depend? The answers are important to conservation efforts and the management of our own interactions with the animals as they pass around, over, and through human communities.
Tiger sharks are present throughout the islands at all times of year. The female sharks' migration from the Northwestern Hawaiian Islands dovetails with the tiger shark birth season in September to early November -- and with the months of highest shark bite risk. Though rare, shark bites have historically been most frequent from October to December. Traditional Hawaiian knowledge also warns of danger during the fall months.
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