Do Japanese macaques add flavor to their meals?

When you pour kibble into your dog's bowl, does your pet ever add condiments like ketchup before eating? Or perhaps your cat mixes tartar sauce into its fish-based meal?

Probably not. Adding seasoning to food appears to be a distinctly human habit. Humans have been using salt to enhance flavors since as early as 10,000 B.C. [source: UK Food Standards Agency]. Roman soldiers were even paid partially in salt, which is where the term "salary" originates. Nowadays, most households have a well-stocked spice collection.

However, a group of Japanese monkeys, also known as macaques, defied this idea in a 1950s study. As you might expect, Japanese macaques live on all Japanese islands except Hokkaido. Their habitat ranges from subtropical to subarctic climates, making them the northernmost nonhuman primates globally [source: Gron]. Adapted to cold environments, these monkeys have thick brown or gray fur and bear a striking resemblance to pink-faced Ewoks.

Macaques typically form groups of 30 to 40 individuals, known as troops, which are led by males. They alternate between tree-dwelling and ground activities, with females showing a preference for staying in the trees [source: Gron]. Once males reach sexual maturity, they leave their natal groups to roam among various troops for mating opportunities [source: Tanhehco].

Macaques are highly adaptable when it comes to food. Studies show they consume over 213 plant species, along with insects and soil, earning them the classification of omnivorous creatures [source: Gron]. In Ohama Park, Osaka, captive macaques have been placed on restricted diets due to overeating. Years of accepting snacks like bread and candy from visitors have led to obesity, with one monkey weighing 63 pounds (29 kilograms), double the species' average [source: Ryall]. Park authorities now discourage feeding the monkeys to prevent overindulgence.

But do these versatile eaters care about flavor? Do they season their food? Discover more on the following page.

Social Learning in Macaque Troops

Imagine you're at a pizzeria with friends, and someone orders a pizza topped with anchovies. You've never tasted anchovies and initially reject the pungent fish. However, after seeing your friends relish the anchovy slices, curiosity gets the better of you, and you take a bite. The experience changes your perspective, and the next time you order pizza, you include anchovies.

A comparable form of social learning occurred among Japanese macaques on Koshima Island in the 1950s. Researchers studying these monkeys offered them sweet potatoes to encourage them to come into the open, making observation easier.

Typically, the monkeys would remove dirt from the potatoes by brushing them with their hands to avoid damaging their teeth. However, in September 1953, a female macaque named Imo advanced this behavior by washing her potato in a freshwater stream. Over time, this habit spread, and by 1958, six of Imo's nine family members adopted the practice [source: Carpenter]. By 1965, the behavior had been passed down to younger generations, and the monkeys began using saltwater instead of freshwater. They would dip their potatoes repeatedly, suggesting they enjoyed the salty taste. Researchers concluded that the behavior had evolved from cleaning to seasoning the potatoes.

Masao Kawai, the lead researcher, published these findings in 1965 in the journal "Primates," titled "Newly-acquired pre-cultural behavior of the natural troop of Japanese monkeys on Koshima islet." The title doesn't mention food because the monkeys' preference for salt was incidental. The study's significance lay in demonstrating that macaques could develop basic cultural practices through social learning.

Examining how the saltwater-dipping habit spread among the macaques reveals insights into the development of new behaviors. Continue reading to explore how this unique potato seasoning practice became a troop-wide phenomenon.

Monkey Behavioral Patterns

Eba, Imo's mother, was the first to adopt the potato-washing behavior. Female macaques in the troop were more inclined to wash their sweet potatoes compared to older males. Since male macaques leave their original troops upon reaching mating age, they have fewer opportunities for social interaction and exposure to new behaviors within the group. This lack of social engagement explains why older males were less likely to adopt the habit [source: Carpenter].

Age significantly influenced whether monkeys adopted potato washing. Younger monkeys, particularly those under two years old, were more open to trying new behaviors. This is due to the inverse relationship between age and brain plasticity—the brain's capacity to form new neural connections essential for learning. Studies on macaque behavior further support this, showing that younger individuals exhibit greater innovation and less resistance to change.

A comparable trend emerged when researchers introduced caramel candy to the monkeys. Juvenile and infant macaques were the first to sample the candy, with adults following their lead. This demonstrates observational learning in macaques, as younger individuals often pioneer new behaviors that adults later adopt.