Examining dolphin hydrodynamics provides clues to calf-loss during tuna fishing

‘dolphin-friendly’ tuna knows that dolphins can be unintended victims of the tuna-fishing industry. Now, a mathematical model shows that dolphin calves can gain up to 90% of the energy required for swimming if they position themselves correctly relative to their mothers, but that the calves are in danger of being lost if this positioning breaks down [1]. As observations of dolphins in the wild support the model (see ‘The bottom line’ box for a summary of the findings), the new work starts to give a possible explanation why dolphin numbers remain at unnaturally low levels despite changes in the tuna-fishing industry aimed at protecting dolphin populations.