Some shark species are able to navigate to specific locations up to 50km away, a new study published in the British Ecological Society's Journal of Animal Ecology has found. Re-analysing tracking data from tagged sharks, ecologists found that while some species such as blacktip reef sharks swim in a pattern known as a "random walk", others such as tiger sharks can at times hunt for prey or mates by using "directed walks", accurately navigating long distances across open ocean, often at night.
To maximise lifetime fitness, animals should optimise search patterns for finding food, mates and safety. In new and unfamiliar locations, animals use different types of random walk. However, many animals occupy large home ranges where they will develop mental maps of the locations of resources and use directed walks (movements to known goals) to move between these locations. Few studies have quantified directed walks in animals.
A team of US ecologists re-analysed tracking data from three species tiger sharks, thresher sharks and blacktip reef sharks. Working out whether or not sharks were using random or directed walks was difficult, as the researchers had no way of knowing where the animal wanted to go. But the researchers were able to tell the difference between a random walk and directed walk by looking at the shape of the sharks' movements at different spatial scales. They compared the overall distance the sharks had moved to those estimated by random walk models, mathematical equations that predicts how far an animal will move if it is moving randomly at these different scales.
They found that although blacktips swam randomly within their small home ranges, both tiger and thresher sharks used directed walks at times. They also found that adult thresher sharks swam with more directed walks than juveniles, and that tiger sharks used highly directed walks to swim to specific locations as far as 50km away.
According to lead
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