Far in the distance, an eagle hunts its reindeer prey
Golden eagles have been filmed hunting and attempting to kill reindeer calves.
One eagle was filmed swooping down and grabbing a calf, while another pulled out of an attack at the last minute.
A BBC natural history film crew gathered the extraordinary footage along a reindeer migration route in northern Finland.
It finally proves this eagle species does occasionally hunt reindeer, something suggested by forensic evidence and the local Sami people.
The crew filmed the behaviour while capturing footage of the reindeer migration for the BBC natural history series
though the images were shot at too far a distance to be included in the final cut of the high definition programme.
In the last 100 yards it went into a low powerful glide and hit the back of a calf
Dr Ted Oakes
Television producer Dr Ted Oakes, cameraman Mr Barrie Britton and scientist Mr Harri Norberg set out to film the hunt along the northern edge of Finland.
For his PhD thesis Mr Norberg has spent the past few years studying how predators interact with the reindeer (Rangifer tarandus), which are known as caribou in North America.
Mr Norberg would tag calves, then search out those that had stopped moving to find out what had killed them.
By examining the bodies and the size and shape of claw, bite or talon marks, he ascertained that the majority of reindeer calves killed in the region had been attacked by eagles.
But he had never actually witnessed such an attack.
"It is also something that the Sami had always told people and complained about but people didn't believe them," said Dr Oakes.
Migrating to safer pastures?
So to get documentary evidence of the behaviour, Dr Oakes and his colleagues used four-wheeled bikes and the advice of local Sami reindeer herdsmen to follow the reindeer along their migratory route.
Striking a new camp every few days or hours, the crew kept up with the animals as they moved out of the forest and into more northern, open and mountainous land.
The reindeer travelled there to avoid wolves and biting insects such as mosquitoes.
"When the reindeer get out in the open, that's when the eagles have a chance," said Dr Oakes.
The film crew captured a handful of successful and aborted attacks on camera.
"One of the things I witnessed was an eagle up a kilometre high and it put its wings up over its head and it fell in a bizarre way, vertically," Dr Oakes described.
"Then in the last 100 yards it went into a low powerful glide and hit the back of a calf."
"This is an extremely dangerous thing for an eagle to do, because the prey is much larger and heavier."
A near miss, as the eagle abandons its attack
To kill a reindeer, the birds strike it in a specific region in its withers, driving their talons into the mammal's lungs.
"They are not killing anything instantly so they have to ride like a rodeo cowboy on the back of the calf," explained Dr Oakes.
"No wildlife filmmaker has ever filmed this before."
"Another one was when the eagle came down and landed near to the calf and was trying to make up its mind," he said.
"I think it had misjudged the approach to the calf and ended up on the ground. It was staring at the calf thinking whether it should have another go and the mother reindeer ran in and scared the eagle away."
More often than not the golden eagles (Aquila chrysaetos) appeared to attack white calves, rather than tan or brown ones, though the crew did not know why.
According to Mr Norberg, it is usually immature golden eagles that kill the calves.
However, he also believes the birds occasionally hunt adult reindeer.
Another larger species of eagle lives in the region, the white-tailed eagle, but this bird is less aggressive than the golden eagle, and will often be chased off a reindeer carcass by its smaller relative.
The Sami people that live in the area say they have seen white-tailed eagles also killing reindeer, but this behaviour has yet to be scientifically documented.
The BBC series Lifeis broadcast at 2100BST on BBC One each week from Monday 12th October.
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