Sharks search for food like humans in a supermarket

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Sharks search for food in the ocean in a similar way to which humans do in supermarkets, the first-ever analysis of the foraging behaviour of marine predators has revealed.

The study, carried out by behavioural ecologists, mathematicians and engineers from the UK, USA, Australia and New Zealand, found that sharks and other marine predators hunt using a pattern of movement known as the ~Levy Walk .

The Levy Walk system is composed of a series of small motions used to search in a specific area, followed by a large jump to a new location rather than continuing to search between the locations.

It is believed that this system of hunting increases the sharks chances of finding prey in a sparse ocean, while also saving energy, as opposed to a more systemic system.

As well as sharks, the study recorded the foraging behaviour of a range of electronically tagged marine organisms, including tuna, cod, sea turtles and penguins, right across the world.

The foraging data obtained revealed similarities when compared to data on the distribution patterns of prey, suggesting that the predators had evolved the Levy Walk system of hunting to obtain the most efficient results from the vast, sparse environment of the ocean.

We developed a computer model from the foraging data, and this confirmed that the observed patterns were indeed optimal for naturally dynamic prey fields. The search rule seems to be a general solution for success in complex and changeable environments, said Dr David Sims of the University of Portsmouth.

The Levy Walk system is very similar to the way that humans shop, said Dr Sims. If you go to the supermarket to buy eggs you look for them in one place, and if you don t find them there you choose another location to look in. You probably won t start at one end of the supermarket and search every aisle.

For more information, see the paper: Sims, DW, Southall, EJ, Humphries, NE, Hays, GC, Bradshaw, CJA, Pitchford, JW, James, A, Ahmed, MZ, Brierley, AS, Hindell, MA, Morritt, D, Musyl, MK, Righton, D, Shepard, ELC, Wearmouth, VJ, Wilson, RP, Witt, MJ, Metcalfe, JD (2008) - Scaling laws of marine predator search behaviour. Nature, vol. 451. pp. 1098-1102.