Dive buddies
What’s it like to shake hands with a wild grey seal? Diver Ben Burville reveals the secret world of Britain’s biggest, most endearing carnivore.
Micky, the skipper of Glad Tidings 7, skilfully coxes the boat as the hull thumps against white-crested waves en route to the research site. I look out across the steely waters of the North Sea and in the distance see the ‘Galápagos of the North’ – the Farne Islands. I have come to associate the archipelago with genuine peace and tranquillity. Home to about 5,000 grey seals, the underwater world around the Farnes is somewhere I feel comfortable.
For the last 17 years I have been observing seals in their element – below the surface – all around the UK coast. At the Farnes in particular I’ve spent hundreds of hours in their company. By day I work as a GP, but I also have a marine biology degree and am a visiting researcher at Newcastle University. The scientist in me tries to avoid anthropomorphism, but I’m in no doubt that seals have personalities. Often, though, I’m left with more questions than answers.
Why, for instance, does a 200kg wild grey seal approach you underwater, hold your hand with its front flippers and respond in kind to a gentle squeeze? Anyone who has dived at the Farnes, Scilly Isles or Lundy, off North Devon, may have experienced a nibble of their fins, a close swim-by or even closer encounters with these inquisitive mammals.
Some people will protest that seals and humans should not interact, that it’s dangerous for both parties and causes disturbance. In certain circumstances, I would agree, such as when seals are hauled-out and feel vulnerable. In the water, however, they’re usually
in complete control of any encounter. Unless a seal chooses to investigate you, the only time you will see one is if you happen to come across an individual sleeping in the shallows. As a rule I suggest divers avoid touching seals. On the other hand, it is often the seals that initiate such contact. And they appear to enjoy it.
Over the years seals have taught me how to behave around them. They respond to minute changes in my buoyancy, speed of movement and breathing. This has given me the opportunity to record previously unseen behaviour, leading to the inception of Project Grypus, a study to collect high-definition video and acoustic recordings of underwater grey seal behaviour. The project is run in coordination with Newcastle University’s School of Marine Science and Technology, under the guidance of Per Berggren.
VENTURING BELOW
Zoologists have long studied hauled-out seals and used radio telemetry to gain insight into their behaviour at sea, yet little research has been conducted on their behaviour underwater, where they spend most time. Project Grypus aims to gain knowledge that may influence conservation efforts.
Back on board Glad Tidings 7, I make final adjustments to my diving equipment. I film seals using a tiny GoPro camera mounted on a metal ‘tray’, attached to which is a sophisticated hydrophone which detects sound waves, originally designed for cetacean studies. Finally ready, I step off the stern into a green-tinted world. Underwater visibility is good, in excess of 6m, and I adjust my buoyancy as I sink.
Seals immediately approach and glide along below and beside me. Their grace and speed make my underwater swimming efforts look feeble, and while I empty compressed air from the 15-litre cylinder strapped to my back, my ‘dive buddies’ can hold their breath in excess of 20 minutes. With large amounts of oxygencarrying myoglobin in their muscles and the ability to slow their heart rate to below 10 beats per minute, grey seals can dive to over 300m.
“SEALS APPROACH AND GLIDE ALONG BELOW AND BESIDE ME. THEIR GRACE AND SPEED MAKE MY UNDERWATER SWIMMING EFFORTS LOOK FEEBLE.
One of my buddies approaches and presses its soft, leathery nose firmly against my mask. I look deeply into the eyes of my companion who stares back, unblinking. For a moment, my breathing stops. There is complete calm. Then a deep base sound reverberates through my chest as another ‘dive buddy’ calls ahead. This one is a large male weighing up to 300kg. The sound seems to attract female seals, who investigate the bull, suspended mid-water with perfectly balanced buoyancy.
A grey seal bull is a formidable carnivore and the heaviest wild animal to breed in the British Isles. Yet these charismatic creatures have two very different sides: there’s the hauled-out seal, cumbersome and defensive, and there’s the same seal underwater, inquisitive and at one with its aquatic environment.
Born on rocky outcrops or in sheltered rocky coves between September and December, a typical grey seal pup weighs 15kg. For the next three weeks it suckles maternal milk that is over 50 per cent fat and puts on a further 30kg, tripling its birthweight. During this early stage, the pups are vulnerable to birth complications and injury from other seals. They are born with white fur, or lanugo, which camouflages them during snowy winters.
Lanugo lacks the insulating properties of more mature fur, and with storms and strong currents the young pups could be carried away and drown. Recently we rescued a pup washed into a powerful current by a rogue wave. It was a strange experience, performing a cross-chest tow on a seal pup that seemed quite relieved to be plucked from the cold water. The pup was returned to its birth beach where, with luck, its calls will have been detected by its mother.
After three weeks the pups tend to form small groups called ‘weaner pods’ while the hungry mothers return to the sea to feed. A week or two later they finally take their first swim. Pup mortality is high – as few as half will reach adulthood. Project Grypus has discovered a location that appears to be an assembly area for young seals such as these, so it is hoped that recordings made here will offer further glimpses into the lives of juvenile seals.
Male grey seals can live over 25 years and will breed from about seven to eight years of age, while females will breed from around the age of five; the oldest recorded female was 46 years old. Along the way seals face all manner of risks, from starvation to entrapment in fishing gear, disease and respiratory infections. Offshore there is also the potential for attack by the occasional orca on Britain’s western, northern and north-eastern coasts, or even by a shark. Life for a grey seal is tough.
NEW DISCOVERIES
The Farne Islands is one of the largest North Sea breeding grounds for grey seals, with 1,876 pups born in 2015 (the most since the early 1970s), but not all is well. “The mortality rate for pups on the Farnes has been very high in recent years,” says Per Berggren. “So improving our understanding of the seals’ behaviour is crucial for future monitoring and conservation of the colony.” Project Grypus may help, because it is the first study to combine video and acoustic data.
At the moment the project is in its early stages but I have already been fortunate to observe remarkable interactions, including bull seals engaging in submerged
‘wrestling’. We believe that the outcome of these sparring matches may be remembered, thus serving to reduce violent confrontations on land. I have also seen underwater courtship and mating, which supports DNA studies published in 1999 that indicated in-water mating may be more important than hitherto realised.
Among the more intriguing pieces of behaviour is unusual ‘rubbing’ activity, displayed mainly by young seals, especially at the site identified as a juvenile assembly area. They use their hind flippers to drive their shoulder and back areas into the seabed. There is debate among marine biologists about the purpose of this behaviour, but it appears to have a social function as well as being a satisfying scratch.
Diet is another area where new discoveries are being made. Traditionally, grey seals in the North Sea have fed mostly on sandeels, cod, whiting, haddock, ling and flatfish (sole, plaice, dab and flounder), eating 4–7kg per day. But recent research has highlighted stranger items on the menu. Jan Haelters, Mardik Leopold and their co-workers have confirmed that grey seals will sometimes kill and eat porpoises, despite the fact that the cetaceans are faster swimmers. It is thought that this is likely to be learned behaviour originating from the opportunistic consumption of drowned porpoises caught in fishing gear.
Another highly unusual behaviour, documented recently by ecologist Sean Twiss and a team from Durham University, involved a large bull grey seal killing and eating a number of seal pups at the Isle of May in the outer Firth of Forth, another major breeding ground for the species. This cannibalism was not an isolated incident, either.
In spite of these revelations, grey seals have reliably shown themselves to be incredibly gentle underwater. They also appear to have an extraordinary understanding of what is integral to my body and what is equipment. This can result in comical encounters, in which a seal will try to locate my mask strap and pull off my mask with surprising dexterity. Reassuringly, seal researcher Sue Wilson has suggested that such behaviour may be mutually beneficial, and that this diver-seal interaction merely represents redirection of normal play activity. (Incidentally, I never use any form of bait when diving with seals.)
TAKING A SMALL SHARE
All too often we underestimate the intelligence of wild animals, and my experiences to date lead me to conclude that grey seals are far more clever than many of us assume. This is important, because even now around Britain and Ireland some people are prepared to shoot seals – perfectly legally, if done under the correct licence – that they believe are stealing ‘their’ fish at coastal fishing sites and around salmon farms. This is despite the fact that alternative methods to deter seals, such as tensioned anti-predator nets, may work at some of these locations, and that seals take less than one per cent of the total biomass of fish in the North Sea.
From the sea’s surface we only ever get a glimpse of seals’ complex lives, so I hope that my work will help to change perceptions and give them a brighter future. I have no doubt that there are many grey seal secrets yet to discover beneath the waves.