Why spend 60 years studying seals?
In 1951 a small organisation called the Northumberland Natural History Society took an interest in the hundreds of grey seals that lolled on the tiny beaches of the Farne Islands off the north east coast of England.
Every year the seals would crowd ashore and give birth to their pups. The local nature enthusiasts decided to try to find out more about the pups that were born there.
"At that point, we knew hardly anything about grey seals," David Steel, the National Trust's head warden on the Farne Islands tells BBC Nature.
"So they decided to tag 10 newborn pups to see if they could find out where they went, and if they returned to the islands to have their own pups."
End Quote David Steel National Trust
When you're born in November on a rock in the North Sea, it's a tough start to life”
So, at the beginning of the pupping season, the team attached cattle clips - metal tags marked with the name and address of the organisation - to 10 seal pups' tails.
Three weeks later, the trust received a letter from Norway. A fellow naturalist there had found seal pup number one alive and well on a beach in Stavanger, approximately 650km (400 miles) from the Farne Islands.
John Walton is the islands' property manager. He works for the National Trust, which owns the site.
"That pup swam 400 miles in a maximum of 14 days," he explains. "It was the first real indication, ever, of the distances seals could travel."
This was the beginning of a project that has now been running for 60 years, studying Farne Island grey seals' lives and behaviour.A tough beginning
Mr Steel is now in the midst of this season's seal count.
Between early October and early December, 1,500 seal pups will be born. Almost half will not make it past the first three weeks of life.
"The pups have to stay out of the water for the first three weeks, when they have their white coat, which is not very waterproof," explains the warden, who spends nine months of the year on the islands.
"But when you're born in November on a rock in the North Sea, it's a tough start to life."
Storms often wash young pups into the water. And occasionally, young, inexperienced mothers abandon their pups and head out to sea.
"We lost 41% last year," says Mr Steel. "Mother Nature certainly keeps them in check."
Despite the early challenges for every newborn seal, the Farnes population is healthy and slowly and steadily growing. There are almost 4,000 seals on a set of islands, which is designated a Special Area of Conservation (SAC) - meaning it is protected under EU regulations.
This successful human safeguarding of the seals' habitat is a huge turnaround; just a few decades ago, the seal population was deliberately decimated.
The animals used to be thought of as a threat to local fish stocks. And during the late 1960s and 1970s, thousands of seals were shot in a cull that aimed to protect the local fishing industry.
- Grey seal females are called cows, males are bulls and juveniles are called pups
- Bull seals can live for up to 25 years, while cows can live up to 35 years
- Adult animals have about 10cm of insulating blubber under their skin
- Seals' whiskers are so sensitive that they are able to pick up the shapes and sizes of their prey from the trails they leave in the water
According to the National Trust, between 1962 and 1983 approximately 2,000 adult females and 3,000 pups were shot.
Mr Steel explains that local fishermen "hated the seals". "They were still shooting small numbers until the 1990s," he tells BBC Nature.
But, as the fishing industry collapsed, it was gradually replaced by tourism. Today, several companies use fishing boats to take groups of people to visit the islands and admire the scenery, seabirds and, of course, the grey seals that make their homes in this bleakly beautiful place.Follow that seal
Over the years, researchers have moved beyond monitoring the seal population to find out more about the animals.
Dr Bernie McConnell from the Sea Mammal Research Unit at Scotland's University of St Andrews has been studying the animals of the Farnes for 25 years.
He and his research team have worked on the islands for weeks at a time studying grey seal biology.
In one of their most recent projects, the team fitted adult seals with hi-tech data loggers that monitored the animals' movements. These tags glued on to the seals' fur and simply fell off when they moulted.
They work like mobile phones, explains Dr McConnell: "As soon as the seals come near shore, they phone their data home."
This data includes location, which the tags measure via the GPA satellite system, and the depth the animal is at - measured via a pressure gauge.
"We can reconstruct the dive profiles of the animals," says Dr McConnell.
"They dive almost continually day and night; 80% of their time at sea is spent underwater.
We don't call them divers, we call them surfacers. Even though they're air-breathing mammals, just like us, that's where they spend the bulk of their time."
Part of the reason for tracking the seals in such detail is to ensure that their habitat is protected. The conservation status of the islands means they must be maintained in a way that is favourable for the seals.
"When they're at the Farnes, they forage within 50km of the [islands], but they're quite capable of travelling further afield," says Dr McConnell.
"There are boundaries to the protected areas and we've shown that the seals move way outside these boundaries.
We have to safeguard the food supply out in the North Sea... and allow them to complete their life cycle."
The research also continues to reveal some of the remarkable ways in which these mammals have evolved to live in the water - withstanding huge pressures to dive up to 70m and using their super-sensitive whiskers to track the wake trails left by the fish they hunt.
And since seals are near the top of the food chain, they rely on a healthy marine environment to feed and survive.
"If the seal population is doing ok, it's one big indication that things are ok in their environment," says Dr McConnell.
"They're a window into the health of the seas."
Follow @BBCNature on Twitter