Grey seals filmed clapping underwater for the first time
A sound made by grey seals that was thought to have been a vocalisation is actually produced by male seals clapping their hands underwater.
No other marine mammals are known to make sounds in this way.
Grey seals are highly social animals, living in colonies of up to thousands of individuals. They make a number of vocalisations to communicate with each other, and it has now been shown that they will also clap their hand-like forelimbs together to make an cracking sound.
With the short, sharp sound cutting through any background hubbub while underwater, it's thought that these noises are used as a form of display for rival males in the area and any females who may be close by.
Dr Ben Burville, a researcher at the University of Newcastle, has been diving with grey seals off the north-eastern coast of England for decades, observing and filming their behaviour. He has finally been able to capture this behaviour on film for the first time.
'I was surrounded by grey seals when I first saw a large male clap underwater,' explains Ben. 'The effect of the clap was instant and rival males rapidly dispersed.
'The clap was incredibly loud, and at first I found it hard to believe what I had seen. There was very little warning of the clap and it was only performed once. This probably explains why it took me so many years to record and film.'
A warning and a display
Grey seals are the largest of the two species of seal found in UK waters, with an adult male reaching up to 2.5 metres long and an impressive 400 kilogrammes in weight. They breed in several colonies around the shores of the UK.
One of the largest breeding colonies in the UK is found on the Farne Islands, off the north-eastern coast of England, and contains up to 6,000 individuals. It is in these waters that Ben regularly dives with the animals.
Underwater recordings previously taken at grey seal colonies have documented loud snapping sounds before, but they were assumed that these were vocalisations. This was based on the knock-like noises that are commonly produced by the closely related walrus.
Instead, the video footage shows that the loud sounds are actually produced by male seals repeatedly clapping their paw-like forelimbs. The noise is produced by the sheer force of the limbs striking each other.
'The discovery of "clapping seals" might not seem that surprising - after all, they're famous for clapping in zoos and aquaria,' says David. 'But where zoo animals are often trained to clap for our entertainment, these grey seals are doing it in the wild of their own accord.
'Depending on the context, the claps may help to ward off competitors and/or attract potential mates.'
David compares these clapping noises to that of the chest-beat performed by dominant male gorillas. One the one hand they a warning to other males in the local area, as demonstrated by Ben's observation of rival males swimming away, but on the other they may be a signal of strength to the females.
While other species of marine mammals, such as whales and dolphins, are known to make percussive noises by striking their tails and flippers against the surface of the water, this is the first time any have been found to clap.
Grey seals are found right across the northern Atlantic, and so it is likely that the grey seals off the Farne Islands are not the only ones that are doing this. Clap-like sounds have been reported in several different colonies, so it's probable that this behaviour is relatively common among the males.
Dr Travis Park, a postdoc researcher at the Museum and at the University of Oxford, whose research includes investigating the anatomy of seal limbs, was also involved in the study.
'No other species of marine mammal have shown this behaviour before,' explains Travis. 'Seals that have more hydrodynamic forelimbs, like fur seals and sea lions, are probably not capable of this.
'But other seals that are in the same group as the grey seals also have a more paw-like forelimb, and so they could very well be capable of clapping too. We just need people to go and film them.'
There is, however, a word of warning about interacting with seals. They are large, wild animals that can be ferocious predators, known not only to hunt fish but also on occasion other marine mammals.
'Please note that grey seals are large wild animals with powerful bites,' says Ben. 'Their mouths contain a variety of potentially dangerous bacteria.
'All my diving around seals is done on their terms. No food or bait is ever used as this would alter behaviour and would be potentially dangerous. Seals must be respected at all times.'