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Although Sable Island is known for its wild horses, it's also home to the world's largest colony of grey seals (Halichoerus grypus). In the United States, their name is spelled as gray seals.

Grey seals on South Beach, Sable Island
Grey seals on South Beach, Sable Island
Photo © Barb & Ron Kroll

An Adventure Canada cruise to Sable Island provides everything you need to know about grey seals. In our case, the more we learned, the more fascinated we became about this North Atlantic pinniped (marine mammal with flipper limbs).

How many seals?

The grey seal population on Sable Island is about 400,000. The number varies by year and season.

Historically, the population is far higher now than a century ago when there were only 500. In 1895, sealers took more than 1,000 seal skins from Sable Island, as well as hundreds of barrels of seal oil.

The population of pups also changes annually. Recent surveys show that the number of Sable Island grey seal pups increased to 50,000 last year.

Juveniles born on Sable Island can be found on the Scotian Shelf and in the Gulf of St. Lawrence. They return to the island to breed when they are four or five years old.

Where can you see grey seals?

It depends on the time of year. Our first view was from Zodiacs as we approached North Beach on the Nova Scotia island. Grey seals were hauled out like boulders along the long stretch of sand.

Adventure Canada passengers in Zodiac view grey seals on North Beach
Adventure Canada passengers in Zodiac view grey seals on North Beach
Photo © Barb & Ron Kroll

The second time, we observed them as we walked across South Beach, where they snuggled together by the surf, sandblasted by the ever-present wind.

Breeding season

According to Jonathan Sheppard, Sable Island National Park manager, who accompanied our group on the walk, the grey seal breeding season is December, January and February.

Jonathan Sheppard, park manager
Jonathan Sheppard, park manager
Photo © Barb & Ron Kroll

"In winter, seals spread out all over the island, become aggressive and hold their ground," he explained. Bulls establish their territories and mate with all cows within reach.

Cows and weaners

After the pups are born, their mothers nurse them for about three weeks. The cows and weaners (weaned pups) head to the high dunes.

During our visit in June, the seals were skittish. Sheppard ensured that we approached quietly and kept our distance. "We don't want to alarm them. If frightened, they will jump into the ocean."

"Grey seals don't stay in family groups," he added. "They congregate in one mass even though there is lots of room to spread out."

We watched the seals bask on the sand. A tail popped up and then a head. The seal looked around, scratched its body with a flipper, and then plopped back down again to snooze.

Interactions with wild horses

Do grey seals interact with Sable Island horses? "Seals are more tolerant of horses than people," said researcher Zoe Lucas, who also accompanied Adventure Canada passengers on the walk.

"I've seen horses sniff basking seals, which snarled and lunged at them. Twice, I saw horses bit by seals, but for the most part there is not much negative interaction."

She explained that when grey seals are pupping, they can displace horses from places where they graze. When they are inland, seals also flatten some of the grasses that horses eat.

Grey seal carcass on North Beach
Grey seal carcass on North Beach
Photo © Barb & Ron Kroll

Shark predators

During our Sable Island walks, we were surprised to see seal carcasses and placentas on the sand. They were evidence of the cycle of life. Gulls scavenge them for food. The rest decays into life-giving nutrients.

Although some seals died from natural causes, others died from shark-inflicted wounds. Research papers published by Zoe Lucas and her colleagues indicate that they were attacked by white sharks and Greenland sharks.

What sounds do seals make?

We heard a variety of grey seal sounds during our visit—groans, grunts, snorts and sighs, often drowned out by the crashing surf.

When they poked their heads out of the water to watch us in our Zodiacs, the seals were wide-eyed and silent.

Species and size

A major advantage of visiting Sable Island on an Adventure Canada cruise is the access it provides to a team of resource staff. During his natural history lecture, Dalhousie University biology professor, Bill Freedman, explained that there are five species of seals on Sable Island—grey, harbour, harp, hooded and ringed.

"Only the grey and harbour seals (Phoca vitulina) breed here," he said. While doing research, he noted that the largest aggregates of seals were on the east and west tips of Sable Island.

Marine biologist, Ree Brennin
Marine biologist, Ree Brennin
Photo © Barb & Ron Kroll

Differences between grey and harbour seals

How can you tell them apart? Grey seals are Canada's largest seal, weighing up to 990 pounds (450 kilograms). Harbour seals are smaller—less than 130 pounds (58.5 kilograms) and shorter—up to 6.6 feet (2 meters) long.

Harbour seals have feline-like faces. Marine biologist, Ree Brennin, another onboard lecturer and scientist, helped us identify grey seals. "They have Roman noses," she explained. They are also called horsehead seals based on their profiles.

Pelt color

"Grey seal pups are white when they are born on the sand," added Brennin. Young males, after molting, are deep-black with a few scattered grey spots. The pelt of molted females is the opposite—silver-grey, with several small dark spots. (Our visit, in June, was during the molting season.)

You can also identify seals by their nostrils. The grey seal has wide-set nostrils, while the harbour seal's are heart-shaped.

Seal research

On Sable Island, Adventure Canada cruise passengers had the opportunity to meet with W.D. Bowen, a grey seal researcher at the Bedford Institute of Oceanography in Dartmouth, Nova Scotia. He has studied seals for several decades.

The Dalhousie University professor has published several papers about seal behavior, such as changes in buoyancy when they dive pre-breeding and post-molting and their dive depths and time spent on the bottom of the ocean.

Satellite GPS tag and acoustic transceiver for tracking grey seals
Satellite GPS tag and acoustic transceiver for tracking grey seals
Photo © Barb & Ron Kroll

Tracking instruments

We were intrigued by the Crittercams and instruments used to track seals. Don Bowen showed us a satellite GPS tag that he affixes to seals. "It transmits their locations every 15 minutes when they come to the surface."

How long do seals dive? Eight minutes on average, according to Bowen.

He showed us an Argos PTT transmitter that sends the seal's location to four satellites in orbit around the world every time the seal comes to the surface. "It also transmits its dive depth every 10 seconds," he explained.

The results showed that grey seals are continental shelf animals. "There are no family groupings or social bonds in grey seals. They travel as individuals," said Bowen.

"VHF transmitters only work on land. We catch grey seals, when they are hauled out on the beach, by cutting them off from the rest of the group with ATVs.

"We then use 10-minute epoxy on a nylon fish net to secure the instruments to the heads of males and the nape of the necks of females." Data is transmitted from the units' sensors when the seals bob their heads above the water.

Don Bowen, grey seal researcher, shows Adventure Canada passengers map of tracked seal locations
Don Bowen, grey seal researcher, shows Adventure Canada passengers map of tracked seal locations
Photo © Barb & Ron Kroll

Acoustic transceivers

Newfoundland fishermen often blame the appetites of millions of seals for the depletion of Atlantic cod. "They kill cod and only eat the liver," one fisherman told us.

As a result, Don Bowen's studies about the diet of grey seals are very important.

He showed us data from five years of tracking grey seals with transceivers that provided acoustic messages about their foraging locations. Bowen's team also tagged bluefin tuna, cod, salmon, snow crab, American eel and other species.

What do grey seals eat?

"We can distinguish fish that seals eat based on fatty acid signature analysis of their blubber," he explained. "It appears that the grey seal's favorite foods are small salmon, herring and redfish."

Although grey seals do eat some cod, current evidence from his data suggests that seals don't deplete cod stocks.

How much does a grey seal eat? According to Don Bowen, an adult male eats about 15.4 pounds (seven kilograms) per day, while an adult female eats about 11 pounds (five kilograms) a day.

Our visit to the biggest colony of grey seals in the world was informative as well as fascinating.


Adventure Canada

Sable Island National Park Reserve

More things to see & do on Adventure Canada Sable Island cruises:

Gully Marine Protected Area - Habitats for Seabirds and Whales

Sable Island Birdwatching - Gulls, Terns, Petrels and Ipswich Sparrows