NYT: Drinking mammals

The human species now has drinking partners.

German scientists have discovered that seven species of small mammals in the rain forests of western Malaysia drink fermented palm nectar on a regular basis. For several of the species, including the pen-tailed tree shrew, the nectar, which can have an alcohol content approaching that of beer, is the major food source — meaning they are chronic drinkers.
Frank Wiens and Annette Zitzmann of the University of Bayreuth were separately studying two of the species, including their eating habits. They discovered that the nectar of the bertam palm becomes fermented by yeast carried on the flower buds.
The pen-tailed tree shrew, in particular, takes advantage of it. By watching the animal and analyzing fur samples, the researchers estimated that the tree shrews consumed enough alcohol that they had about a 36 percent chance of being intoxicated (by human standards). But the researchers never saw any signs of inebriation, and from an evolutionary standpoint, it makes no sense to be drunk anyway. With predators all around, Dr. Wiens said, “it’s just too risky for an animal.”
The findings, reported in The Proceedings of the National Academy of Sciences, suggest that the tree shrews and other animals have some efficient means of metabolizing the alcohol. The findings also suggest there must be benefits to having chronic low levels of alcohol in the bloodstream — otherwise the behavior would not have evolved.
Those benefits may be psychological, Dr. Wiens said, perhaps enabling the animals to cope with stress of some sort. Further studies to determine the benefits may help in understanding humans’ relationship to alcohol, he said. And since tree shrews are similar to species that were precursors of primates more than 50 million years ago, studying their alcohol use might also provide some evolutionary background for human drinking, he added.