It was a beautiful morning in the Scilly IslesA group of islands off the coast of Cornwall in south-west England. as the biosecurityMeasures aimed at preventing the spread of harmful organisms. officer made her morning rounds. She had had a wonderful time watching the seabirds. But suddenly she saw something that horrified her. Coming ashore were the birds' greatest enemy: rats!

Rats can be extremely destructive, which is why the British government is giving a large amount of money to combat them.

They pose a serious threat to seabirds, eating their eggs and chicks. Storm-petrels, puffins, gannets, terns and razorbills are particularly at risk.

The Scilly Isles are a vital breeding ground for these birds. With the sea to protect them, they ought to be safe - but rats can swim for three days, as well as stow away on boats.

Storm-petrels only breed in two places in Britain - "and if rats get to those islands, the consequences are dire", according to Jaclyn Pearson, a Scilly Isles conservation officer.¹

One island saw its storm-petrel population plummet from 20 breeding pairs to five. Although the rats have now been eliminated, constant surveillance is needed to stop them coming back.

Some people, though, think we should have more respect for the invading rodents. "Although I wouldn't want one in my house, I do admire rats," says the TV presenter Iolo Williams. "Of all wildlife, they've adapted to live alongside us better than any other animal."

Rats have very good memories, and a strong visual sense. They can remember up to 30 events, and tell a film that contains a rat from one that does not. 

They are also very good at learning, and finding their way around mazes. Experiments at Leuven University in Belgium suggested that rats were actually better than humans at some tests.

The reason, the researchers decided, was that humans always look for rules about how things work - even if there are none. Rats have a simpler approach, but it can be more effective.

And though they are destructive, they cannot really help it. Because their teeth grow around four inches a year, they have to gnawChew. on things to keep them under control.

Humans have not always had a low opinion of them. The Ancient Egyptians and MayansA complex civilisation that lived in modern day Central America from around 2000 BC. Eventually ruined by famine and conflict, the last Maya city was conquered by Spain in 1697. worshipped rats, and the Romans considered them lucky.

Yes: At least in some tests, according to the researchers at Leuven. The fact that there are so many of them shows that they are clever enough to survive and thrive in many different environments.

No: They have very small brains compared to ours, and can only do a limited number of things. They are not about to produce great works of literature or send a rocket into space.

Or... Sometimes not being brilliant is a good thing. If humans had not been so ingenious in inventing machines to exploit fossil fuel, we would not have such huge environmental problems.