English Audio Request

In the wild, on a tennis court-sized enclosure, they had a terrain of grass, stones and straw bales, and obstacles like ladders. There was a supply of pellets but they also discovered and tasted berries, an apple, a snail, an egg and even a dead bird. The lights went out when the sun set, and the weather fluctuated from sunshine to rainstorms.
The white and Lister-hooded rats in the experiment had been bred and kept in labs since such testing began in 1908 - which, given that rats can breed every three months, makes them at least the 200th generation.
The conclusions are obvious, according to Berdoy. 'We have taken the animal from the wild, but we have not taken all the wild from the animal.'
His experiment unfolds in an award-winning internet film which has attracted interest from several TV companies. The first thing the released rats did was to venture out to explore the new terrain - led by the male hooded rats which, before they did anything, went to find their female white companions.
After that the animals soon found water, and began experimenting with new foods, a far cry from the pel lets their many ancestors lived on in labs.
It then took little time for the rats to start finding burrows for protection - even though they would never have been threatened in such ways before.
Even after six months, the lab rats were bolder or more naive about risk than their wild cousins, but they still showed a remarkable instinct for self-preservation. When they met their first-ever cat in the farmyard they immediately took refuge - suggesting an 'innate aversion' to cat odours. And the females took the precaution of storing food for pregnancy - even though they had always been fed daily. Within hours the lab rats had also adopted a 'hopping gait' characteristic of wild rats, and began to dig, something they could not do before.
Within days they began to establish a hierarchy along traditional lines. The bigger ones remained dominant once they had won an encounter, even when they were outgrown, showing that age meant something.
They also established a network of runs between key locations of food and shelter which the rats navigated by smell so effectively they did not have to look where they were going - again as they do in the wild.