Keeping Mice Happy

German scientists say laboratory mice that are kept entertained by having toys in their cages respond the same as mice that live in empty cages, a finding that will surely boost the animal rights activists' campaigns for researchers to treat lab animals humanely.

The millions of mice and rats used each year in labs for testing are bred according to strict criteria so that they are all the same size, weight and have the same genetic background. The animals' standard housing is small, empty cages, which are thought to make the creatures anxious and even cause impaired brain development.

Skewing scientific results?

Many researchers are concerned that mice that are treated differently could deviate from the norm and, thus, skew the outcome of experiments.

University of Giessen animal physiologist Hanno Würbel and colleagues have challenged this assumption. They used 48 female mice, drawn from two standard breeds, and either housed them in standard cages or in large "enriched" cages where there were tunnels, trapezes and other objects to stimulate them.

The mice then took part in four experiments that are classically used in behavioral research -- finding their way through mazes and responding to new objects. The rodents performed the same in both tests, thus showing that an "enriched environment" had no effect on the outcome.

Not just for behavioral research

Strictly speaking, the results of Würbel's experiments apply only to behavioral research. But Würbel says they should be just as relevant in other branches of lab research.

"They should also apply to animals' physiology or anatomy, which are, in any case, less sensitive than behavior to environmental perturbations," he said.

The study appears Thursday in Nature, the British weekly science journal.