Tracking Endangered Whitetip Sharks: They're Actually Homebodies
Sharks may not be the extroverts that we once thought. A new study shows that oceanic whitetip sharks are more homebodies than anything else, revisiting areas that they're familiar with.
The study, published in PLOS One, tagged several sharks in order to track their movements. Since the whitetip shark is classified as a vulnerable species globally and critically endangered in some parts of their range, it's crucial for scientists to understand what areas to protect in order to save the species.
Oceanic whitetips are named for the distinctive white patches at the ends of their fins. They possess powerful jaws and are opportunistic; because of this, they're considered one of the more dangerous sharks to humans, according to BBC News, though the number of unprovoked attacks is relatively small.
In recent years, their numbers have drastically declined, in part due to shark finning. The practice involves catching sharks, cutting off their fins to use in delicacies such as shark fin soup, and then often throwing the rest of the body back into the ocean where, if the shark is still alive, it will drown.
Fortunately, protections are now being put into place. The Bahamian government has now banned all shark fishing in the 240,000 square miles that make up the country's waters. The sharks themselves are a valuable resource-especially while still alive. According to the Pew Charitable Trusts and BBC News, the sharks provided $78 million to the Bahamas' economy in the form of tourism over 20 years.
These sharks, though, remain surprisingly elusive. Only four tagged whitetips have been recaptured, and only a few have been tracked by satellite in the central Pacific. This lack of data prompted the scientists involved in the study to tag 11 adult whitetips to monitor the sharks' movements. These tags were then programmed to detach at a predetermined time which ranged from 30 to 245 days. Then, the tags would upload the location data to a satellite.
Overall, the researchers found that six sharks stayed very close or within the Bahamas Exclusive Economic Zone, which is an area that is slightly larger than France. Five others stayed within 310 miles of Cat Island for a month before fanning out across the western North Atlantic. Even so, all but one of the sharks came back to the Bahamas before the last tag dropped off.
The research shows that the sharks preferred to stick close to their "home" areas. One of the researchers involved in the study theorized that the pattern may have been related to the 2-year reproductive cycle; females may head out to breeding grounds to find mates or to birthing grounds to give birth. In order to test this, researchers are planning to use ultrasound and a yet-to-be-developed hormone-based blood test to detect whether or not female sharks are pregnant.
These findings could give scientists another way to help preserve this particular species of sharks. Since they return to the same areas, these locations can be protected in order to give the whitetips a better chance at survival.
The researchers aren't done tracking these sharks yet, though. They tagged an additional 41 sharks to get more data on their movement this past summer.