Consumer survey: Caged mink value water

Researchers have used principles of human economics to figure out how mink regard fur-farm conditions.

Even after 70 generations in captivity, caged American mink still seem to miss the swimming they would do in the wild, say Georgia J. Mason and her colleagues at Oxford University in England.

They set up each of eight male and eight female mink in its own warren of compartments. All had a typical mink cage, with seven added chambers featuring various attractions. For example, one chamber held a pool of water, and another offered a different novelty, such as a traffic cone, each day.

To measure what the mink were willing to “pay” to enter a particular chamber, the researchers required the animals to push against weights to gain entry. The more weight the animals were willing to push, the more they presumably wanted what was inside the chamber.

In this system, the mink rated the swimming pool as “their most valuable resource,” Mason and her colleagues report in the March 1 Nature. In order to swim, the minks pushed a total of 17 percent more weight during the experiment than they did to get access to their second-most-popular chamber, one holding hay.

A second test found that cortisol, a stress hormone, jumped 33 percent in animals cut off from the pool, once they knew it was there, but not in those kept away from the hay.

“These results suggest that caging mink on fur farms does cause the animals frustration, mainly because they are prevented from swimming,” say Mason and her colleagues.

“The take-home message of their paper, however, is that science can inform arguments about animal welfare by providing objective evidence about how animals respond to captivity, ” comments veterinary researcher Michael Mendl of the University of Bristol in England.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.