Gunshot-loud underwater clapping could be how grey seals intimidate rivals and attract mates
It's like chest-thumping for the agile marine mammals
For the first time ever, grey seals have been captured on video clapping their flippers very loudly in a show of strength and warning to other seals.
Marine mammals like whales and seals usually communicate using vocal calls and whistles. Marine biologist Ben Burville from Newcastle University in England, who has been studying and diving with grey seals off the Farne Islands for more than 20 years, was used to these vocalizations.
In fact, when he first heard the sharp snapping sound when diving with seals back in 2002, he assumed it was simply one seal vocalizing to another. But, in subsequent years, he was able to witness the true source of that sound.
It wasn't a vocal call at all, but the seals clapping their flippers powerfully together under water, producing a noise he compared to a gunshot. And recently, Burville captured it on video for the very first time.
What is all the clapping about?
Seals in zoos and aquariums are famous for clapping, but they're trained to do it, usually for a food reward. In contrast, the seals Burville observed are doing it under water in the wild. His video shows a male grey seal clapping its front flippers together to make a very loud crack sound in the water.
It seems that only the males, which can be 200 to 300 kilos, make the sound. This led researchers like Burville and his colleague David Hocking, a research fellow in the School of Biological Sciences at Monash University in Melbourne, Australia, to conclude that the male makes the sound as a show of strength to warn off competing males and possibly attract mates.
How is that sound even possible under water?
The clapping is a powerful underwater noise. It is a high frequency sound that cuts through any background noise. It is sometimes accompanied by a reply clap from another male in the distance. But without air to compress between the flippers, Hocking was mystified as to how the sound was actually being produced.
This led him to a local swimming pool to experiment with human underwater hand-clapping. As it turns out, underwater clapping is not audible above the surface of the water, but is quite loud below the surface. The sound easily travelled the entire length of the busy pool.
Now that this behaviour has been identified, Hocking feels that we need to be careful not to disturb this sound. Human noise pollution has been known to interfere with whale song. In a similar way, man-made noise in the oceans could be impacting the mating habits of grey seals.
Written and produced by Mark Crawley