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.

BBC Wildlife Magazine - - Grey Seals - BEN BURVILLE is a visiting re­searcher at New­cas­tle Univer­sity and a keen diver. For 17 years he has spent ev­ery spare mo­ment in the water with seals.

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.

Com­ing face to face: Ben Burville has spent hun­dreds of hours diving with grey seals off the coast of Northum­ber­land to study their fas­ci­nat­ing un­der­wa­ter be­hav­iour.

Top left: A play­ful grey seal tries to take off Ben’s mask. He says he would trust any seal in the water more than any do­mes­ti­cated dog on land. Above: Ben makes eye con­tact with his ‘dive buddy’.

Top right: a young grey seal rubs its back on rocks. The pur­pose of this be­hav­iour is de­bated but it could have a so­cial func­tion, or be just a way of get­ting rid of an itch. Right: a cu­ri­ous adult male nib­bles at Ben’s gloved hand.

Top left: Ben helped res­cue a grey seal pup that was washed into a pow­er­ful cur­rent by a rogue wave. Top right: three seals in­ves­ti­gate Ben at the sur­face. Above: with just over 111,000 grey seals, UK coasts are home to roughly 38 per cent of the species’ world pop­u­la­tion.

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