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Fossil foragers

Posted by Hayley Dunning Jul 15, 2014

Researchers discover evidence of optimal foraging strategies, which are found across the animal kingdom today, in 50-million-year-old sea creatures.


How do you find food in a wide landscape? Foraging for scarce resources requires an optimal walking strategy: you have to cover lots of ground without going back over your trail or getting disoriented by obstacles.


The optimal strategy is a mathematical pattern called a Lévy walk, and researchers - including Museum palaeontologist Prof Richard Twitchett - have just discovered that it appeared at least 50 million years ago in ancient sea urchins.


Walking to the same beat


A Lévy walk consists of lots of shorter steps, indicating an intense hunt for food in one area, interspersed with a few longer steps, as the animal travels between searching areas. It's observed today in everything from sharks and insects to modern human hunter-gatherer tribes.


By analysing trace fossils - the trails imprinted in rocks by creatures walking over the sea bed - Prof Twitchett and colleagues were able to find the first evidence of Lévy walks in extinct animals. They think the foraging strategy of a Lévy walk may have arisen as a response to decreased food availability after past climate change and mass extinctions.



A: Trace fossil trail of an ancient urchin. B: Digitised version of the trail, showing a Lévy walk pattern.


Window on the past


Prof Twitchett said:

'It's amazing to think that 50 million year old fossil burrows and trails have provided us with the first evidence of foraging strategies in animals that live on and in the deep-sea floor - studies which would be nearly impossible and very expensive to do in modern oceans. Trace fossils are remarkable and beautiful records of the movements of ancient animals which have been frozen in time and tell us so much about the evolution of life on Earth and the environments of the past.'