Spider Monkeys Are Experts At Sniffing Out The Best Fruits

Spider monkeys are experts at sniffing out the very best ripe fruits, as revealed in a recent study from Linkoping University and two German universities.

In the experiment, five spider monkeys were tested for their ability to distinguish different types of fruit odors at a field station in Mexico. The study was carried out by Rosa Orts Garri, a masters student, along other researchers and Prof. Matthias Laska, professor of zoology at Linkoping University, according to a news release.

The monkeys were presented with mixtures of ten substances that resembled the fruit of two tropical tree species, which were in varying stages of ripeness. The task was to select the best fruit, which the monkeys could do in more than 70 percent of the attempts.

"Distinguishing between the ripe and the completely unripe odor - they learned this in one day. And when the mixtures were made more similar to each other, the monkeys could still tell the difference quickly," said Laska.

The study found that the monkeys use their sense of smell to identify ripe fruit in nature. The monkeys learned to associate the odor of ripe fruit in the wild when they were rewarded with the taste of delicious fruit, similar to the experiment, in which they were rewarded with a tidbit of sweet fruit when they selected the right mixture, according to the news release.

The study revealed that the interchange between the fruit eating primates and the tropical trees is an example of co-evolution, where each species adapt to each other's needs over millions of years. For many animals, the fruit has a higher value when it contains more sugar and nutrients.

"This adaptation goes back some fifty thousand years, when the first primates appeared. Initially they ate mostly insects, before eventually trying fruit and vegetables. Some fruit didn't want to be eaten, so they developed toxic substances. Others acquired better and better odors that signaled energy-rich sugar and nutrients," Laska said.

Most primates and tropical bats can determine the best fruits by smelling them. However, birds are more attracted to bright colors, they are less inclined to smells, according to the researchers.

The study concluded that a species' sense of smell cannot be considered "good" or "bad". Spider monkeys that eat fruits from various plant species learn to differentiate between complex scent mixtures. 

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