Image copyright Tauana Films

In 2012 Valentin Gruener rescued a young lion cub and raised it himself at a wildlife park in Botswana. It was the start of an extraordinary relationship. Now an astonishing scene is repeated each time they meet - the young lion leaps on Gruener and holds him in an affectionate embrace.

"Since the lion arrived, which is three years now, I haven't really left the camp," says Gruener.

"Sometimes for one night I go into the town here to organise something for the business, but other than that I've been here with the lion."

The lion he has devoted himself to is Sirga - a female cub he rescued from a holding pen established by a farmer who was fed up with shooting animals that preyed on his cattle.

"The lions had killed the other two or three cubs inside the cage, and the mother abandoned the remaining cub. She was very tiny, maybe 10 days old," Gruener says.

The farmer, Willy de Graaf, asked Gruener to try to save her and so he took her to a wildlife park financed by de Graaf and became her adoptive mother, "feeding her and taking care of her".

"You have this tiny cute animal sitting there and it's already quite feisty," he says. "It will become about 10 times that size and you will have to deal with it."

She's much bigger now, but when Gruener opens her cage she still rushes to greet him - ecstatically throwing her paws around his neck.

Media playback is unsupported on your device Media caption The lion leaps on Gruener as they meet. Video courtesy of John Hawkins.

"That happens every time I open the door. It is an amazing thing every time it happens, and it's such a passionate thing to do for this animal to jump and give me a hug," says Gruener.

"But I guess it makes sense. At the moment she has no other lions with her in the cage and I guess for her I'm like her species. So I'm the only friend she's got. Lions are social cats so she's always happy to see me."

The companions spend their time hanging out in the Botswana bush, doing the kind of things that cats enjoy, such as lying around under trees, play-fighting, and hunting.

"I don't believe we have to teach the lion to hunt. They have this instinct like a domestic cat or even a dog that will try to hunt. Any cat will catch a bird or a mouse. The lion will catch an antelope when it gets big enough," Gruener says.

"I'm definitely giving her that opportunity to hunt, about three times a week at the moment. Each walk takes five hours - sometimes up to nine. We sort of hunt together and I'm helping her sometimes, trying to show her how to kill something rather than catch it."

After Sirga's first kill Gruener wasn't sure if it would still be safe for him to get close to the lion. But "she let me come in", he says. Now he despatches animals the lioness fails to kill quickly enough.

"It's a bit cruel because she will catch an antelope and hold it down, and when it gets tired she could simply go and bite it in the throat and kill it. But because it's so exciting she's like a cat that keeps on playing with the mouse.

Image copyright Tauana Films

"It's not so lovely to watch when a lion has an antelope in front of her and she's having fun playing with this antelope."

Willy de Graaf has handed Gruener 500 hectares (two square miles) to create a "miniature park" in which Sirga can roam freely, but she will not be released into the wild. Not because she could not survive, Gruener says, but because she has lost her fear of humans.

Under those circumstances she is likely to get too close to humans, and if there is an accident she will end up getting shot. "And that's not really the whole point of raising a lion," Gruener says.

In the park Sirga can live like a wild lion, but remain safe, he says. "That's the plan for her future."

And what of his own future? Gruener has put aside work on a PhD while he has been raising Sirga, and has hardly ever left her alone.

"If she gets into a bigger enclosure and gets more space, and maybe another lion to give her companionship, I'm sure I would be able to leave for longer periods of time - which is required for me to finish my studies.

"But as long as she needs me, and as long as I feel I want to be there to make her life better, I will have that as my priority.

"I doubt anything will change much between me and her."

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Valentin Gruener spoke to Outlook on the BBC World Service. Listen again on iPlayer or get the Outlook podcast.

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