Is this monkey really cuddling a pet mongoose?

A tender moment or something more sinister?

The image appears to show a bonobo cuddling a little mongoose like a treasured pet. But instead, maybe the monkey took the mongoose pup for dinner after killing its mother.

But that would be unusual - bonobos mainly eat fruit and only occasionally hunt.

The intriguing behaviour was photographed by Christian Ziegler in Democratic Republic of Congo.

His fascinating picture has been selected as a Highly Commended image in the Natural History Museum's Wildlife Photographer of the Year (WPY) 58th competition.

The shortlist was revealed on Thursday, and the overall winners will be announced at London's Natural History Museum (NHM) in October.

Christian had been tracking the group of bonobos "chest-deep through flooded forest" in the Salonga National Park for days when he spotted the young male holding a juvenile mongoose in his hand.

"I was so surprised to see how he carried the mongoose with such care. I immediately started to follow him and document it," he told BBC News.

The monkey held and stroked the small mongoose for over an hour, he said.

But he may have been planning to eat him. When bonobos catch prey, they do not immediately kill it, but instead start eating when it is still alive, according to Dr Barbara Fruth, director of the LuiKotale Bonobo Project which has been observing these animals for over 20 years.

But occasionally, if dinner is too big and the ape gets full, it will treat the leftover living prey as pets. Usually, these animals are later eaten.

Dr Fruth believes that this is probably what was happening in the picture.

She does highlight that bonobos are known for their gentle, empathetic and peaceful nature.

"We know from captivity that bonobos care for individuals other than their own species," she says. In the wild, it's unlikely that a bonobo would take care of another species as a long-term pet, she adds.

But she does not exclude the idea that the apes keep other animals as accessories to attract interest from other group members and thereby increase their status.

In the end, this mongoose had a happy ending - the bonobo eventually released his "pet", who then got away unharmed.

The mystery behind the photo is part of its attraction to the judges of the Natural History Museum's contest.

Senior researcher at the Natural History Museum Dr Natalie Cooper whittled down nearly 40,000 entries across 20 categories with her fellow judges. "We're looking for technically, really brilliant images - the ones that you see once and wake up in the morning still thinking about," she says.

WPY has become one of the most prestigious competitions of its kind. Entries from 93 countries were received for this year's event.

The category and Grand Prize winners will be announced at a Natural History Museum ceremony on 11 October. The museum will then open its annual exhibition of the best photos on 14 October.

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