Oxygen mystery: How marine mammals hold their breath
14 June 2013 Last updated at 10:36 BST
Scientists say they have solved the mystery of one of the most extreme adaptations in the animal kingdom: how marine mammals store enough oxygen to hold their breath for up to an hour.
The team studied myoglobin, an oxygen-storing protein in mammals' muscles and found that, in whales and seals, it has special "non-stick" properties.
This allowed the animals to pack huge amounts of oxygen into their muscles without "clogging them up".
Victoria Gill reports.