April 19, 2013
Research Shows Great White Sharks Enjoy Their Hawaiian Vacations
Brett Smith for redOrbit.com — Your Universe Online
"This study is valuable in that it provides a better understanding of the biology and behavior of white sharks, which is very useful for management purposes,” said co-author William Aila, chairperson of the State of Hawai'i Department of Land and Natural Resources. “White sharks were caught by pre-contact Hawaiians, and their teeth used in weapons and other implements. But in many ways they continue to mystify us today."
According to the researchers, their study showed previously unknown habits and behaviors of the deadly and often misunderstood predators.
Most notably, the team found female white sharks visit Hawaii on a two-year reproductive cycle, during which they return to coastal sites near California and Mexico on alternating years. This means they tend to spend more time in Hawaii, where the warmer waters may speed up fetal development.
"Male and female white sharks have different migration patterns," explained co-author Kevin Weng of the University of Hawaii — Manoa's School of Ocean and Earth Science and Technology (SOEST). "Males have been recorded in Hawai'i from December through June, but females have been observed here all year round.
“We learned that white sharks occur in Hawai'i across a broader part of the annual cycle than previously thought — we recorded observations from every month except November,” he added. “This is important for our understanding of white shark life history and population."
In the study, the authors analyzed information from a range of sources, including verified shark sightings, catch-and-release records, images from various sources, and satellite tracking data. They excluded any instances where the species could not be definitively confirmed as a white shark.
The researchers noted their findings are consistent with another recent study in the journal Animal Biotelemetry.
While satellite tracking technology has added to the recent advances in studying shark behavior, it has left many questions unanswered.
"Our satellite tracking studies have been conducted in places where we can get very close to the animals — seal colonies — but this means that we may be sampling a subset of the population, and thus obtaining biased results," Weng said. "It is possible that there are individuals that do not aggregate around seal colonies."
Misidentification of sharks has also been confounding research efforts. Similar looking sharks, such as makos, make cataloging the activity of Great White sharks difficult. Video surrounding the sighting of a mako shark near Oahu, on Jan. 12, 2012 "went viral" and was widely reported as a white shark. Many news outlets continue to misidentify other species as Great Whites.
Besides revealing new details on the habits of white sharks, the study also proposed a method to help distinguish between makos and Great Whites — head shape, as mako sharks have a more acute head shape than white sharks. Since photographic evidence of a sighting typically includes only a shot of the shark´s head, scientists said the method would be helpful for most situations.