SCIENCE FOCUS

Roaches: It's not about looks, but personality

Cockroaches with individual characters? What next, world domination?

PUBLISHED : Sunday, 08 February, 2015, 8:41am
UPDATED : Sunday, 08 February, 2015, 8:41am

Comedian Dayo Wong Tze-wah turned out to be right about cockroaches: they are not just disgusting vermin but have individual personalities.

That's the latest scientific finding. If people can be divided into extroverts and introverts, well, scientists have discovered the insects may be classified as "adventurous" or "shy".

Back in the early 2000s, TVB had a popular sitcom, War of the Genders, which starred Wong as Yu Lok-tin, a badly educated paralegal who fancied himself a ladies' man and kept a cockroach called Siu Keung as a pet. To the intense annoyance of his flatmate, a legal eagle played by Dodo Cheng, he called Siu Keung his spiritual brother and insisted the bug had personality and communication skills.

Now, scientists at the Université libre de Bruxelles have proved him right. Cockroaches are not just a skittering homogenous mass but have individual character traits, said Isaac Planas Sitjà, a lead researcher at the university.

When they venture out in the open, the shy ones quickly seek shelter and hide away as long as possible. However, others are more adventurous and explore their surroundings. The "cautious" ones may feel safer but have fewer opportunities to find food sources. Those who take risks find more food but are also more easily destroyed.

Writing in the journal Proceedings of the Royal Society B, the research team said: "From studying the way they find shelter, we show that individuals have consistent behaviour which can differ between individuals in a group - cockroaches have personalities."

The cockroaches in the experiment were each attached with a radio tag. They were released in batches to observe the speed and time they needed to find shelter or to explore for food. It turns out the personalities of individuals can also affect the behaviour of others in the same groups. Having diversified traits favours the survival of a species because when disaster strikes, at least those with favourable characteristics have a better chance to live on and pass on their genes.

It has been often claimed that cockroaches would inherit the earth after a global nuclear holocaust. They do have amazing ability to withstand high doses of radiation. In one experiment, the bugs were subjected to varying levels of radiation. Exposed to 1,000 radon units (rads) of radioactive metal cobalt 60, a human would die in just 10 minutes. But half of the sampled cockroaches subjected to the same amount were still alive and kicking after a month.

The bomb dropped on Hiroshima radiated about 10,000 rads. At this level, 10 per cent of the insects survived after a month. The entire group was wiped out at 100,000 rads. The reason for their superior survival ability over humans is that radiation gradually destroys at the cellular level. Cells are most vulnerable to radiation when they divide. But cockroaches have much slower cell cycles than humans.

One way or another, the bugs will probably outlive us. If they have developed personality traits, their descendants may well evolve into intelligent beings, given enough time.