The results suggest that ruffed lemurs primarily rely on a memory of the place, rather than a memory of what turns they took. The other species showed a mix of both strategies.
Finally, to better reflect the situations lemurs face when foraging in the wild, a third experiment tested the lemurs' ability to remember multiple locations. In the initial session, a lemur was allowed to explore a room containing eight open boxes, each marked with a distinct visual cue. Half the boxes were baited with food and half were empty. After the lemur learned which boxes contained food and which didn't, all eight boxes were baited with food and covered with lids to keep it from view. Ten minutes later, when each lemur searched the room again, only the ruffed lemurs preferentially searched spots where they found food before.
In their native Madagascar, ruffed lemurs' diets can exceed 90% fruit -- especially figs. Remembering when and where to find food from one season to the next requires keen spatial skills and good powers of recall. Fruit is only ripe and ready to eat on a given tree for a limited time, and the next fruit-laden tree may be far away in the forest.
Coquerel's sifakas eat mostly leaves, which are easier to find and available for more months of the year. And ring-tailed lemurs and mongoose lemurs -- who finished in second and third place in many of the memory tests -- can grab a snack pretty much anywhere, anytime, Rosati explained.
Animals living in captivity don't have to forage for food in the same way they do in the wild, so the differences the experiments found are probably innate, not learned, the researchers said.
The study is part of a long history of research aimed at understanding the origins of primate intelligence. The most widely accepted idea is that humans and other primates owe their smarts to the demands of getting along in a group. But far fewer studies have examined the idea that some asp
|Contact: Robin Ann Smith|