Moo Deng's protective big sister fought with a monkey.

Moo Tun charged at the primate who was sitting inside its enclosure at Khao Kheow Open Zoo in Chonburi, Thailand.

Footage shows the juvenile hippo sitting on the hay and dashing toward the young macaque causing it to run away.

Hippos are known to be social animals. This behaviour helps them learn social cues and establish relationships within their group. Their playful nature also allows them to explore and learn about their surroundings.

Moo Deng - whose name translates to 'bouncy pig' - is attracting large numbers of visitors to the zoo in Chonburi near the city of Pattaya.

Officials said the zoo has seen record ticket sales since the pygmy hippo exploded in popularity.

From September 1 to 23 alone, weekday attendance surged to 5,000 visitors daily, compared with fewer than 1,000 before Moo Deng. On weekends, numbers surged from at little as 2,000 to more than 10,000.