Beaked whales have developed a unique way to avoid being hunted down by killer whales — they silently dive in groups to depths of around 1,500ft (450m).
This takes them out of range of predatory orcas and allows them to reach the safety of deep waters, lowering the chance of being caught and killed to less than 25 per cent.
They then use vocalisations and echolocation to hunt for food independently before rendezvousing at depths of 2,500ft (750m) and slowly climbing to the surface.
Experts say this behaviour has not been observed in other deep diving whales and the reasons for it are still a mystery.
Scientists analysed data from 26 beaked whales carrying sensors that tracked the depths they swam to, the steepness of their dives, and the sounds they made.
The researchers from University of La Laguna in Spain noticed the marine mammals keep quiet in shallow waters.
They write in their study, published today in the journal Scientific Reports: ‘Biologging data from 14 Blainville’s and 12 Cuvier’s beaked whales show that group members have an extreme synchronicity, overlapping vocal foraging time by 98 per cent despite hunting individually, thereby reducing group temporal availability for acoustic detection by killer whales to <25 per cent.’
They speculate this is to avoid drawing the attention of predators, such as killer whales.
After successfully reaching the deep water, the whales then go off and hunt independently before gathering to ascend.
But their trip to the top takes a shallow trajectory, as they climb slowly.
Researchers say that on average, the return trip can see them emerge around 0.6miles (one kilometre) away from where they started.
But this ascension strategy, although cautious, comes at a cost to the whales.
They can take more than an hour to complete and reduces foraging time by around 35 per cent.
Researchers say the findings suggest predation risk may have been a strong evolutionary force driving the unique diving and vocal behaviour of beaked whales.