The bearded seal, Erignathus barbatus, is the largest seal species in the Arctic, typically reaching lengths of seven to eight feet and weights between 575 and 800 pounds. This marine mammal resides in circumpolar Arctic and sub-Arctic waters, maintaining a close association with seasonal sea ice over relatively shallow continental shelves. This icy, shallow environment fundamentally shapes its life and diet, allowing it access to the nutrient-rich ocean bottom. The seal uses broken and drifting pack ice for resting, molting, and giving birth.
The Core Diet: Benthic Invertebrates
Bearded seals are primary benthic feeders, meaning their diet consists mainly of organisms that live on or in the seafloor. Foraging is generally restricted to depths shallower than 650 feet, ensuring they can easily reach the bottom to find food. This specialized niche leads to a highly diverse intake of bottom-dwelling invertebrates.
Preferred prey includes:
- Various species of mollusks, such as clams, mussels, and whelks.
- Crustaceans, including crabs (especially hermit crabs) and shrimp.
- Soft-bodied invertebrates like sea cucumbers, polychaete worms, and sea anemones.
This diet sometimes gives the seal a unique physical trait; their faces and foreflippers can take on a rust-colored hue from continuous foraging in the iron-rich sediments. The reliance on these seabed creatures means bearded seals compete for food with other benthic feeders, most notably the Pacific walrus.
Specialized Hunting and Foraging Techniques
The bearded seal possesses specialized anatomical features that allow it to successfully locate and capture food hidden within the seabed. The most distinctive feature is their highly sensitive, long white whiskers, known as vibrissae, which give the seal its common name. These vibrissae act as tactile sensory probes, allowing the seal to detect subtle movements and textures of prey buried in the soft sediment of the ocean floor.
Once prey is detected, the seal employs a powerful method of suction feeding. They create a strong vacuum force within their mouth to suck soft-bodied prey, such as clams and worms, directly out of the sediment. This suction-feeding strategy is particularly effective for consuming preferred benthic prey, often allowing them to swallow smaller items whole.
The seal’s foreflippers are relatively small but square-shaped and equipped with strong claws. These claws are used for maneuvering on the ice and for disturbing the sea bottom, helping to flush out or expose prey hidden just beneath the surface. The combination of sensory whiskers, specialized suction, and strong foreflippers makes the bearded seal a highly efficient benthic hunter.
Diet Variation by Season and Location
While the core diet is based on benthic invertebrates, the bearded seal’s menu is also influenced by geography, age, and seasonal shifts in ice cover. In some areas, particularly in the Bering and Chukchi Seas, small demersal fish are a significant component of the diet. These secondary prey items include Arctic cod, polar cod, sculpins, and flatfishes.
Fish consumption increases when benthic prey is less accessible or when schooling fish are abundant. Studies in the Bering Sea show that during the early spring, fish like capelin and codfish may constitute a major portion of the stomach contents. Younger seals also tend to eat proportionally more shrimp than older animals, highlighting age as a factor in dietary composition.
The seasonal movement of sea ice directly impacts foraging success. Feeding intensity is highest during the open-water season when the continental shelf is fully accessible for bottom-foraging. In regions with deep ice cover, the seals may switch to opportunistic feeding on fish and cephalopods, like squid, which are more easily caught in the water column. This flexibility allows the bearded seal to adapt to the changing availability of prey across its vast Arctic range.