Sydney, July 27 - Like animals, trees can camouflage themselves too, a new study has found. One tree even kept changing the colour of its leaves to protect them from a giant flightless bird.

'Plants are attacked by a bewildering array of herbivores and in response they have evolved a variety of defences to deter predators such as thorns and noxious chemicals,' said Kevin Burns from Victoria University, New Zealand, lead researcher of the new study.

'Animals often use colours to hide from predators or advertise defences, but until now there has been little evidence of colour based defences in plants.'

Burns' team studied the leaves of the Araliaceae tree, a species native to New Zealand. This species goes through several colour transitions from germination to maturity, probably as a defence strategy against an extinct predator, the moa.

Before the arrival of humans, New Zealand had no native land mammals, but was home to moa, giant flightless birds, closely related to the modern ostrich and the top herbivore in the food chain.