A customs sniffer dog at Charles de Gaulle airport in Paris was taken by surprise when a suspicious bulge in an arriving passenger's trousers turned out to a live boa constrictor.

A 30-year old Frenchman was found to be trying to smuggle the 40-cm (16-inch) boa into the country undercover.

The sniffer dog latched on to the reptile's scent through the man's bulging trousers, as he disembarked from a flight from the Colombian capital Bogota.

The man told customs officials he wanted to add the snake to his reptile collection.

Boa constrictors are protected under the Convention on International Trade in Endangered Species (Cites), which classifies it as a potentially endangered species which cannot be freely traded.

The boa was confiscated and placed in the temporary care of airport officials.

Ideal pet?

In the United States, boas bred in captivity are sold as pets, with prices ranging from $200 upwards for a Colombian red-tailed boa, which can grow to well over 2m (7 ft) in length.

Strong pigmentation in the tails, fine striping or patterning and extremely light colouring can all increase the price of a boa to well beyond $1,000.

Would-be owners are advised that young boas consume an average of a mouse per week.

Snakes, being cold-blooded, need to be kept in a warm environment, but inside underwear is not normally recommended.