Toothed whales, a diverse group of marine mammals including dolphins, porpoises, and larger species like sperm whales, are active predators in the ocean. They possess specialized teeth, unlike their baleen whale relatives, which equip them for hunting and consuming a variety of prey. These aquatic hunters have developed unique adaptations, allowing them to thrive in diverse marine environments, from shallow coastal waters to the deep ocean. Their predatory nature is a defining characteristic, shaping their behavior and their role within marine ecosystems.
Diverse Dietary Components
The diet of toothed whales is wide-ranging, with different species specializing in various types of marine life. Many toothed whales, such as dolphins and porpoises, primarily consume fish. For example, bottlenose dolphins eat a variety of fish including mullet, sea trout, and flounder, while harbor porpoises mainly feed on schooling fish like herring and mackerel, often near the seabed. Some dolphin species, like spinner dolphins, also include jellyfish and krill in their diet.
Cephalopods, such as squid and octopus, are a significant food source, especially for deeper-diving toothed whales. Sperm whales, the largest toothed whales, predominantly hunt giant and colossal squid, often diving to depths of 300 to 800 meters, and sometimes up to 2 kilometers, in search of them. The circular marks found on sperm whales’ heads sometimes result from battles with large squid attempting to avoid being eaten. While squid form their primary diet, sperm whales also consume various fish and occasionally other items like rays.
Some larger toothed whales, particularly orcas (killer whales), are apex predators with a highly varied diet that extends beyond fish and cephalopods. Orcas are known to hunt other marine mammals, including seals, sea lions, and even other whale species, as well as seabirds and sharks. Different populations of orcas often specialize in specific prey types, with some focusing on salmon while others target marine mammals. Some smaller toothed whales, like dusky dolphins, also consume crustaceans such as shrimp.
Ingenious Hunting Strategies
Toothed whales employ a range of sophisticated strategies to locate and capture their prey in diverse aquatic environments. Echolocation, or biosonar, is a primary hunting tool, allowing them to “see” with sound in dark or murky waters. Toothed whales produce high-frequency clicks by forcing pressurized air through structures called phonic lips in their nasal passages. This sound is focused by a fatty organ in their forehead, known as the melon, and travels through the water until it strikes an object. The returning echoes are received by a fat-filled channel in their lower jaw, which transmits the information to their inner ear for analysis, providing details on the prey’s distance, size, and movement.
Many toothed whale species engage in cooperative foraging, working together to increase hunting success. Dolphins, for instance, often herd schools of fish into a tight ball, known as a “bait ball,” by encircling them. Individual dolphins then take turns swimming through the compacted school to feed while others maintain the formation. Some bottlenose dolphins use “silt netting,” where they create a wall of mud with their tails to trap fish, forcing them to leap into waiting mouths. Orcas also coordinate attacks on larger prey, such as seals, by creating waves to wash them off ice floes.
Toothed whales also use techniques to stun or disorient their prey. Dolphins may use powerful tail slaps on the water’s surface to confuse fish, making them easier to catch. Some researchers suggest that the intense, focused sounds produced during echolocation might also disorient prey. Additionally, certain species, such as beluga whales and some beaked whales, utilize suction feeding, drawing prey directly into their mouths. This method is particularly effective for capturing bottom-dwelling or individual prey items.
Factors Influencing Diet
The diet of toothed whales varies based on several factors, reflecting their adaptability to different ecological conditions. Each toothed whale species has evolved to specialize in certain types of prey, influenced by their size, dentition, and habitat. This specialization ensures efficient foraging within their ecological niches.
Geographic location significantly impacts prey availability, leading to regional dietary preferences. Dolphins living in different areas, such as the Moray Firth in Scotland versus tropical waters, consume fish species prevalent in their local habitats. The availability of prey in a given marine environment shapes the foraging choices of resident toothed whale populations.
Seasonal availability and migration patterns of prey also play a role. Many toothed whales adjust their food intake based on seasonal abundance, with feeding seasons often occurring during warmer months when fish, krill, and squid are plentiful. Shifts in prey populations, such as the decline of herring stocks, have led porpoises to shift their diet to other species like sandeels and gadoid fish. Older or larger whales might target different or larger prey compared to younger or smaller individuals, with juvenile porpoises, for example, initially eating smaller gobies before transitioning to larger fish as they mature.