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Beyond the boundaries of civilisation: Landmark study shows lab rats revert to survival mode within hours when set free. Is it the same for humans?
For more than 200 generations, they have not ventured outside. Yet a remarkable new experiment, which has tantalising implications for human behaviour, has discovered that laboratory-bred rats never forget how to survive in the wild.
Despite not knowing what the natural world looks, smells or even feels like, a group of rodents whose forebears have been kept in cages for the past 96 years showed that their ancient genetic impulses quickly surfaced.
Within hours of being freed, the rats started to return to their 'wild' ways, burrowing and following ancient mating instincts, behaviour which had never been possible when they were caged captives.
People have long thought that the trappings of civilisations could be quickly discarded when mammals were confronted with the necessities of survival.
But far from witnessing a Lord of the Flies -style reversion to a violent, cruel society, the rats formed more of a hierarchical order based on age, showing respect for the older animals and better organisational skills.
Dr Manuel Berdoy, a zoologist at Oxford University Veterinary Services, who put 75 rats into a farmyard and watched and filmed their reactions over six months, said that the results threw light on how our innate instincts work.
'The released rats quickly showed the ghost of their wild ancestors still lies beneath the wild coat of the lab rat, even after so many years of selective breeding [to favour more docile animals],' he said.
'Our rats found water, food and bolt holes almost immediately; within days they had started to establish social hierarchies, and within weeks they had a wide-ranging pattern of runs criss-crossing the colony.'
While Berdoy is wary of making too many links between species, he said: 'There are lots of similarities between rats and humans in that we are successful social omnivores. Certainly they had similar problems to resolve and some of them they resolved in a similar way.'
There could be no greater change of environment for a rat than the difference between the outdoors and a research laboratory. Lab rats are kept in plastic cages - normally with straw, maybe with cardboard tubes to hide in - that are cleaned out at least weekly. There is a constant supply of nutritionally balanced pellets for food, lighting is artificial and on timers, and the heating is controlled to within a few degrees.