Lemurs that stick to an all-fruit diet may have better spatial memory than more adventurous eaters.
The findings suggest that relying on foods that are seasonally available and harder to find gives the animals a "competitive edge," a Duke University news release reported. These individuals are most likely better at remembering where the best fruits are.
Researchers tested the spatial memory of five lemur species: "fruit-eating red-ruffed and black-and-white ruffed lemurs, leaf-eating Coquerel's sifakas, and ring-tailed and mongoose lemurs that eat a mix of fruit, leaves, seeds, flowers, nectar and insects," the news release reported.
The team looked at 64 lemurs' ability to find food in mazes and boxes; they found that fruit-eaters were able to find the treats more quickly than lemurs that ate a mixed diet.
In the first experiment, the lemurs learned where the treats were located in a T-shaped maze. The fruit-eating ruffed lemurs were able to remember this information a week later.
In a second experiment the lemurs were taught how to find a piece of food in a "symmetrical cross-shaped maze." About 10 minutes later the lemurs were released at a different point in the maze and left to find their way to the treat. The ruffed lemurs tended to find their way back to the food.
"Before they might have turned right, but now they had to turn left to get to the same spot," Alexandra Rosati of Yale University said in the news release.
The results suggest ruffed lemurs rely on memory of place rather than direction.
In a third experiment the lemurs were allowed to explore a room with eight covered boxes displaying various visual cues. Half the boxes contained food and half were empty. When the lemurs were allowed to explore the room for a second time (about 10 minutes later) only ruffed lemurs looked in places where they had already found food.
The findings suggest that certain parts of primate intelligence developed to help them overcome everyday obstacles such as finding food.
"Our results [suggest] that different cognitive skills might evolve for different reasons," Rosati said.
