There is a documented record of animals modifying their food. In a study conducted in the 1950s, scientists provided sweet potatoes and other snacks to Japanese macaques (Macaca fuscata) on the beaches of Kojima Island, located in northern Japan.
Initially, most of the small monkeys consumed the vegetables immediately after receiving them, including the sand. However, a young female, known as Imo, began washing her meal in a nearby stream before eating. This behavior was gradually assimilated and replicated by the other young monkeys on the island, leading to the fact that, after a few years, almost all the animals washed the potatoes.
At first, the use of the freshwater from the stream was more frequent to remove the sand. However, on certain occasions, the little macaques also washed the food in the sea itself. Years later, researchers observed that they all started preferring to use the ocean, as the saltwater probably gave the meal a flavor.