The birth of one of the most critically endangered species of monkey has been captured on video at a safari park in Wiltshire.

Longleat Safari Park, in Warminster, is home to Maxi and Rico, two cotton-top tamarin monkies who are critically endangered.

The two monkeys, aged five and six, have now become mother and father after Maxi gave birth to a new cotton-top tamarin monkey at Longleat.

Rare footage of the birth shows father Rico at Maxi's side and the infant, whose gender is not yet known, was born weighing around 40g - approximately the average weight of a chicken egg.

This birth is part of a European breeding programme and marks key progress for the conservation of the species, which is critically endangered due to human activity.

Cotton-top tamarin monkeys are named because of the shock of white hair on their headsCotton-top tamarin monkeys are named because of the shock of white hair on their heads (Image: Longleat Safari and Adventure Park/PA Wire)

 “We weigh Maxi and Rico weekly as part of our usual checks, and we saw her weight gradually increasing," said Abbi Wheeler, a keeper at Longleat.

“Cotton-top tamarins usually sleep through the night, but Maxi was awake for an hour one night which sent an alert via the camera system as it was unusual.

“When we watched we saw her make a jumping movement and we saw a baby climbing around her side and cling straight onto her fur.

“They share parenting as carrying the baby takes up a lot of energy so mum holds while feeding and then dad carries the infant.

“It is really exciting as Maxi and Rico are the first breeding pair at Longleat, and they are critically endangered as there are only around 6,000 in the wild."

In the late 1960s and early 1970s, 20,000 to 30,000 cotton-top tamarins were exported to the United States for biomedical research, specifically as subjects of studies related to colon cancer.

Although this is now illegal, deforestation in the Colombian tropical rainforests where the monkeys are from continues to pose a significant threat to their survival.

It is expected that the new infant will be fully weaned at around 15 weeks old when the monkey will then move to its main diet of insects, fruits, plant exudates, flowers, nectar, eggs and smaller vertebrates.

Visitors to Longleat will be able to see Maxi, Rico and their new baby in their enclosure in the Animal Adventure area.