"To find out whether that was all there was to it," said Richard W. Byrne, a study co-author, "we reanalyzed the data looking only at the temperature of the days in between the last visit and the revisit. The effect held up."
The team also ruled out other sensory clues, like smell, by focusing only on the trees with unripe but insect-rich fruit. Again, the effect held up.
So, Byrne said, "we're as sure as anyone could be that the only way a monkey could know whether to head for [trees with unripe fruit with insects inside] from 50 or 100 yards [150 to 300 feet] away was by using its memory."
Overall, the mean temperature of the days between visits was the best variable for predicting the monkeys' behavior, Byrne says.
"That showed us that the monkeys were really using the weather to predict whether a revisit was worthwhile—the exciting result."
Free Email News Updates
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
|
SOURCES AND RELATED WEB SITES
|
