The sperm whale (Physeter macrocephalus) is the largest of the toothed whales and the world’s largest toothed predator. This marine mammal is instantly recognizable by its massive, square-shaped head, which can account for up to one-third of its total body length. Found in all deep oceans worldwide, this species is a highly specialized hunter, adapted to pursuing prey in the perpetual darkness of the deep sea.
The Primary Prey: Deep-Sea Squid
The vast majority of the sperm whale’s diet is composed of cephalopods, primarily various species of deep-sea squid. Evidence of this specialized diet is often collected by examining stomach contents from stranded or deceased individuals. Indigestible squid beaks accumulate in the whale’s stomach, recording the species and size of prey consumed.
Among these, the giant squid (Architeuthis dux) and colossal squid (Mesonychoteuthis hamiltoni) are the most famous prey, representing a significant challenge and reward for the whale. Physical evidence of these battles is commonly seen on the whales’ heads, where circular scars are left by the suckers and sharp hooks of their struggling prey.
Squid meat generally has a low caloric content, meaning the whales must consume immense quantities daily. A single adult can consume approximately one ton of food per day, equating to about 3 to 3.5 percent of its body weight. This high volume of feeding is necessary to obtain the energy required for its demanding lifestyle as a deep-sea diver and predator.
Secondary and Opportunistic Food Sources
Sperm whales are not typically active predators of large, healthy baleen whales. Their long, narrow lower jaw contains teeth that fit into sockets in the upper jaw, a structure poorly suited for tearing large chunks from massive prey. This morphology is instead optimized for grappling and securing the slippery, soft bodies of squid and deep-sea fish.
The idea of a sperm whale engaging in a sustained hunt against a large baleen whale is extremely rare in modern observations. Predation on other cetaceans is primarily the domain of the orca, or killer whale. However, sperm whales are opportunistic feeders; they will consume smaller cetaceans or scavenge on the carcasses of dead whales that sink to the ocean floor, a phenomenon known as whale fall.
Their secondary diet varies significantly depending on geographical location and local prey availability. In regions like the Gulf of Alaska, demersal fish can constitute a considerable portion of the diet, sometimes making up almost half of the total intake. These supplementary items include large, bottom-dwelling species like skates, rays, and various deep-water sharks, such as sleeper and basking sharks. These prey items are often swallowed whole, facilitated by the sperm whale’s wide throat, a feature uncommon among other whale species.
Hunting Strategies and Deep Diving
Sperm whales have evolved physiological adaptations for deep-sea hunting. They routinely undertake foraging dives reaching 600 to 800 meters, though they can plunge to depths exceeding 2,000 meters. These dives often last about an hour, allowing the whale extended periods to search for prey in the aphotic, or lightless, zone of the ocean.
In the darkness, the whales rely on echolocation to navigate and locate prey. They produce powerful, rhythmic clicks using the spermaceti organ in their head, generating some of the loudest sounds in the animal kingdom, potentially reaching over 230 decibels. These clicks travel through the water, bouncing off objects to provide the whale with an acoustic map of its surroundings.
When a potential meal is detected, the rhythmic search clicks transition into a rapid burst of sound known as a “buzz,” indicating the terminal phase of the hunt. This buzz is emitted just before the whale attempts capture, often occurring around an average depth of 700 meters. The actual feeding mechanism frequently involves suction, where the whale creates a vacuum to draw the soft-bodied squid into its mouth, often without needing to chew.