The diet of most primates relies on fruits, leaves, and insects, classifying them as omnivorous or herbivorous. Due to this common profile, the consumption of fish is often considered an anomaly. However, scientific observation confirms that some monkeys do eat fish, though this behavior is not universal across the primate order. The consumption of aquatic resources demonstrates flexibility in the feeding strategies of certain monkey and ape species.
The Direct Answer: Piscivory in Primates
The term for fish-eating behavior is piscivory, and it is a recognized phenomenon among a small percentage of primates. Fewer than ten percent of all primate species exploit aquatic resources, suggesting this dietary shift is a specialized adaptation. Species that engage in piscivory typically live near water sources, such as coastlines, rivers, or tidal pools.
The presence of fish in the diet is highly site-specific, often dependent on local ecological conditions and seasonal changes. Consumption is most often recorded during drier seasons when low water levels concentrate aquatic life, making capture easier. This behavior is an active, learned response to environmental opportunities, demonstrating a behavioral plasticity that allows certain groups to access alternative food supplies.
Primate Species Known to Consume Fish
Observations confirm that a number of primate species have successfully integrated fish into their diets across various geographies. The long-tailed macaque (Macaca fascicularis), found throughout Southeast Asia, is one of the most frequently cited examples, often seen foraging in coastal and riverine habitats. These macaques have been recorded scooping up small fish from rivers and are also known for consuming crabs and other aquatic invertebrates.
Another well-documented instance involves the Japanese macaque (Macaca fuscata). Fecal studies confirmed that these “snow monkeys” actively hunt fish, particularly during the harsh winter months when other food sources become scarce. Beyond the macaque genus, other primates observed consuming fish include capuchin monkeys, olive baboons, and chacma baboons. Even great apes like the orangutan have been documented eating disabled catfish, demonstrating that this behavior spans different primate families.
Opportunistic Hunting Techniques and Nutritional Role
The methods primates use to acquire fish are generally opportunistic and reflect a creative use of their environment and dexterity. Long-tailed macaques, for example, commonly use a simple scooping technique, rapidly plunging a hand into shallow water to grab small, trapped fish. Japanese macaques have been filmed actively hunting live fish in streams, suggesting a more deliberate effort to catch prey for sustenance during winter.
Orangutans have shown an even greater diversity of techniques, ranging from opportunistic hand-catches to the use of tools to obtain fish, often targeting vulnerable or disabled prey in shallow, slow-moving water.
This fishing behavior is primarily motivated by the high nutritional value of fish, which offers a concentrated source of high-quality protein. Fish also provide essential micronutrients, including iodine, calcium, and zinc, which are often difficult to obtain from a purely terrestrial plant-based diet. The omega-3 fatty acids found in fish are particularly beneficial for developing juveniles and reproductive females.