Ambam celebrates his birthday. Picture: Charlotte Jones

A gorilla who became an internet sensation when footage emerged of him walking like a man is celebrating his 21st birthday.

YouTube footage of western lowland gorilla Ambam aping humans with his unusual habit of walking upright has been viewed more than five million times.

Today the 500lb beast was joined by fellow primates to mark his milestone at Port Lympne Wild Animal Park near Hythe.

Keepers there marked the occasion by giving Ambam and his group special wrapped presents filled with food.

The clip of Ambam went viral in January, thrusting him into global superstardom.

Head gorilla keeper Phil Ridges said: "Ambam and his group really enjoyed ripping open their presents which were filled with mixed seeds.

"Hiding the food in boxes tested the gorillas' ingenuity so it was a good enrichment for them as well as a special treat for Ambam's birthday.

"Enrichment is really important for animals, particularly an intelligent species like gorillas, as it encourages them to exhibit natural behaviours such as foraging and problem solving."

The footage was filmed by animal researcher Johanna Watson whilst she was working with the University of Manchester for a project on great ape locomotion.