Sharks are fantastic navigators
SHARKS ARE FAMED for extraordinary hearing, motion sensing and smell, but new research shows some species can also navigate with pinpoint accuracy over long distances.
“Simply put, they know where they are going,” said Dr Yannis Papastamatiou of the Florida Museum of Natural History in Gainsville, co-author of a new study. “Many people could walk to a known destination 6-8 km away – but imagine doing it in deep water and at night.”
US ecologists analysed data from eight tiger sharks, nine blacktip reef sharks and 15 thresher sharks which had been tagged with trackers and released off either Hawaii, Palmyra Atoll in the Pacific Ocean or southern California. Each was followed for 7–72 hours.
The blacktip reef sharks all swam apparently randomly within a narrow home range, while the tiger and thresher sharks travelled longer distances, often with a clear sense of direction.
The biggest voyagers were the tiger sharks, which during the study period swam more than 8 km. Some research has tracked this species heading to a goal 50 km away.
“[This] ‘Directed movement’ reflects terrain that is familiar for the sharks, given that they have an interest in saving energy by heading straight towards a target, such as food,” write the study authors.
The mystery remains, though, as to how sharks are able to accomplish these navigational feats. “As anyone who dives knows, finding your way around underwater without a compass is very difficult, but this is what we found tiger sharks could do,” Papastamatiou says.
Theories to explain the sharks’ abilities include “cognitive maps” built on knowledge of ocean currents and temperatures, which act in the same way as visual landmarks on the ground, or perhaps navigation by earth’s magnetic field.
The study appears in the Journal of Animal Ecology.