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Early isolation makes for a dull chameleon

Shy behaviour Chameleons reared in isolation are less colourful and more submissive than those who grow up together, new research has found.

The findings could add weight to the idea that the behaviour of such animals, which are believed to be largely asocial, can be influenced by social interactions in early life.

The research, by PhD student Cissy Ballen at the University of Sydney, and colleagues, is reported in the February issue of Animal Behaviour.

"It's generally assumed these animals are asocial and that environmental factors that these juveniles would encounter during their early development would not affect their social behaviour," says Ballen. "I wanted to test this assumption."

Chameleons, like most reptiles, are believed to lead a fairly lonely existence. While they come together to mate, there is no maternal care of the young.

"The mother oviposits the eggs into a hole and leaves them," says Ballen.

But recent research suggests that early social interactions can affect such animals in their later life.

Chameleons are known to hatch together and disperse slowly so they may well spend time with their siblings, says Ballen.

To investigate the impact such interactions would have on later life, she and colleagues studied the behaviour of about 40 veiled chameleon (Chamaeleo calyptratus) hatchlings in the laboratory.

Some animals were kept in isolation while others were kept in groups of four. After two months, the researchers carried out a number of tests.

Foraging ability

In one test, Ballen put two chameleons together and observed their behaviour for 20 minutes. She also used a spectrometer to record the chameleons' colour as a result of the encounter.

Animals reared in groups showed signs of aggression. They chased the other animal, curled and uncurled their tail, compressed their body and extended their throat.

Those animals reared in isolation, on the other hand, were more submissive in their encounters with others - fleeing or curling into a ball.

During encounters with each other, there was also a very distinct difference in the colour of the two groups of chameleons.

"Those reared in a group would become brighter and more saturated in colour whereas isolated individuals tended to become darker and duller in colour," says Ballen.

In another test, Ballen studied how long it took the animal to gobble up a pinhead cricket placed in its enclosure.

"We used the time from when the cricket was exposed to the animal to when the animal caught the cricket as a measure of foraging ability," she says.

"Those who were reared in groups were able to catch their prey more quickly than those reared in isolation," says Ballen.

She says the findings suggest that being reared in a group, even briefly, could be a benefit to individual chameleons in terms of colour expression and their ability to forage.

Ballen says the next step to confirm the findings, is to extend lab studies to examine the impact of isolation on adult animals. It would also be important to have continuous field monitoring of the animals to confirm findings, she says.

However veiled chameleons, which are native to Yemen and Saudi Arabia, are hard to study in the field, says Ballen.