Zoologists, spurning high-tech testing gadgets, are turning to old-fashioned methods used to measure consumer satisfaction in order to determine the happiness of animals bred in captivity.
For the first time, scientists at Oxford University have used preference tests to analyze what caged animals want and the physiological stress they endure it they don't get it.
"These methods can be used objectively to measure animal welfare and improve their living conditions. We don't have to guess anymore," scientist Georgia Mason said.
Fur-farmed minks cannot fill in surveys or answer questions, so Ms. Mason and her colleagues set up experiments to measure their satisfaction levels and how much they would be willing to pay, in terms of effort, to get something.
Living in a tiny cage and being bred from birth to be slaughtered and worn on someone's back is bad enough, but what minks miss most - more than toys, new nest sites, tunnels or raised platforms - is swimming.
"We found that the animals rated the water pool as the most valuable resource," Ms. Mason said in a study published in Nature magazine.
Despite 70 generations being bred in captivity, mink still hanker to do what comes naturally in the wild. The caged creatures also displayed the highest stress levels when they were cut off from the water pool or deprived of food.
Contrary to arguments suggesting that successful breeding proves minks have adapted well to captivity, the researchers said their study shows minks have still not been domesticated.
"These results suggest that caging minks on fur farms does cause the animals frustration, mainly because they are prevented from swimming," Ms. Mason added.
Scientists may now be able to select the mink least bothered by the lack of swimming and breed them to produce minks that are more content to live in cages.