CLOWNFISH can count to determine whether other fish are friend or foe, research suggests.
Experiments found they appear to identify their own kind from the number of stripes on their bodies.
The orange fish were portrayed as friendly in animated 2003 Pixar film Finding Nemo.
But in reality, they are feisty creatures which aggressively defend their homes from rivals.
Researchers found common clownfish — with three stripes — pursued and nipped their own kind and clownfish with two stripes.
But they did not mind those with one stripe or none.
Study leader Dr Kina Hayashi, of Okinawa Institute of Science and Technology, Japan, said: “Common clownfish attacked their own species most frequently.”
He suggested it may relate to their development.
Common clownfish initially form two white stripes at around 11 days old, before gaining the third three days later.
Dr Hayashi suspects clownfish who grow up with other two-striped youngsters see similar ones as competitors to be chased away.
