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Critically endangered roloway monkey born at Chester Zoo

A baby monkey with black and white fur and big, round eyes holds its hand to its mouth, as it sits with its mum in the sunshine.Chester Zoo

Four-week-old Lagertha is roughly the same size as a tennis ball

There's a very cute new arrival to meet - a four-week-old roloway monkey named Lagertha, who's about the same size as a tennis ball.

But even though she's tiny, experts at Chester Zoo say her birth is a big deal, calling it a "significant moment" for the species.

Roloway monkeys are marked as critically endangered on the International Union for Conservation of Nature's red list, which means that they face a very high risk of extinction in the wild.

The organisation says there are fewer than 2,000 of them living in the wild in the West African countries of Ghana and the Ivory Coast, where they face threats including poaching and habitat loss.

A monkey with black and white fur lies on a table at the vets. A vet wearing a blue uniform and blue gloves gently rests her hand on the monkey.Chester Zoo

Mum Masaya had an operation on her foot just months before she gave birth

Lagertha's arrival is particularly special as her mum, Masaya, had to have a complicated operation for a foot injury just months before she gave birth.

Luckily, her surgery was a success and keepers at the zoo say she's been looking after Lagertha "magnificently".

"Masaya is very important - not just to her family, but to her whole species. There are only a few breeding females in zoos in Europe," zookeeper Zoe Edwards explained.

She added that little Lagertha, who was named after a Viking queen, is "already curious" about her habitat and "inquisitive" about humans.

A little monkey with black and white fur crouches on a rock, whilst its mum stands nearby on the grass.Chester Zoo

Vets say Masaya is "comfortable" and "active" after the surgery

Roloway monkeys have dark grey fur that covers most of their bodies, with a long, white beard and a dark orange marking on their back.

According to the Chester Zoo website, they use these unique colour patterns to recognise each other.

It says that they can also be very noisy and use a variety of distinctive calls, although these can unfortunately make it easier for poachers to find them in the wild.

Sometimes these can sound like chuckles, croaks and even yells.