How do foraging animals find their food? A new study from researchers at New York University shows that lemurs use scent, social cues and long-term memory to locate hidden fruit — a combination of factors that may have deep evolutionary roots.
“Our study provides evidence that lemurs can integrate sensory information with ecological and social knowledge, demonstrating their ability to consider multiple aspects of a problem,” said anthropologist Elena Cunningham, clinical professor of molecular pathobiology at NYU College of Dentistry and lead author . of the research, published in the International Journal of Primatology.
Animals rely on their senses and ecological and social knowledge to find food and water. It is thought that these factors – perhaps in combination – may have played a role in primates developing into larger brains and higher cognitive skills than other animals.
“Historically, there have been two schools of thought on why primates evolved larger brains: ecological pressures, such as the need to find scarce fruits in the forest, and the social pressures of living in a group where everyone tries to outsmart each other. Cunningham said. “I have long been interested in the interplay between social and ecological factors when it comes to cognition – it seems a given that these would have evolved in relation to each other.”
To better understand how primates integrate these factors to find food, Cunningham traveled to the Lemur Conservation Foundation in Myakka City, Florida, a sanctuary dedicated to researching and protecting lemurs outside their native Madagascar. The Foundation is home to several species of lemurs, including brown lemurs: social animals with a keen sense of smell (much better than humans) and whose diet consists mainly of fruit.
The researchers studied the brown lemurs in pairs and groups of three and conducted several experiments by hiding pieces of melon in cardboard takeout containers and placing both fruit-filled and empty containers in the lemurs’ environment. They then observed the groups of lemurs examining and opening the containers, noting their interactions with each other.
Despite there being more empty takeout containers than those containing melon, the lemurs had little trouble finding and eating the fruit – and several factors seemed to work together. The lemurs quickly learned which containers contained food and could remember the location of the fruit-filled containers days, weeks and even months later: the order in which they approached the baited containers was about 50 percent better than chance. But the lemurs almost always (98 percent of the time) opened the fruit-filled containers first, suggesting they used their sense of smell to detect the melon up close.
Furthermore, the researchers noted that the lemurs’ individual strategies for finding fruit were influenced by social factors. Some groups were egalitarian and information and melon were happily shared, while in other, more hierarchical groups, the dominant lemurs took advantage of the subordinates who discovered the melon and helped themselves once the fruit was found. But subordinates were more likely to find the fruit, and some used their “finder’s advantage” to eat more of the melon.
“What our study shows is that these three factors are all working at the same time: the lemurs have memories of where the food is and they take into account olfactory information and social factors,” says Cunningham. “We still have a lot to learn about how this interacts and the evolution of cognition, but it is important not to look at these factors in isolation, but in conversation.”
Other authors of the study are Malvin Janal, Rachelle Wolk and Maria Gonzalez-Robles of NYU Dentistry. The research was supported by the NYU Research Challenge Fund Program and the NYU College of Dentistry Academy of Distinguished Educators Funding Award.
