Seals, marine mammals belonging to the group called pinnipeds, exhibit complex and varied social behaviors that differ across species. Whether they travel in groups depends heavily on the specific species, the time of year, and their current activity. Large numbers of seals resting together are often temporary aggregations driven by external needs rather than true cooperative sociality. Their life cycle involves a flexible social structure, moving between isolated foraging at sea and dense, seasonal colonies on land.
Solitary Existence Versus Social Gatherings
Most seal species are fundamentally solitary during day-to-day activities in the ocean, especially foraging and long-distance travel. For example, the harbor seal is typically solitary and rarely interacts with others outside of mating season. When in the water, individual seals hunt alone, relying on their own skills to capture prey. This contrasts sharply with the cooperative hunting strategies seen in some other marine mammals.
Despite their solitary nature at sea, seals frequently gather in non-reproductive groups on land or ice, known as “haul-outs.” These are simple aggregations where many individuals converge in a limited, safe space for resting and thermoregulation. Though physically close, seals often maintain personal space and may exhibit aggressive behaviors if another encroaches too closely. The group presence provides safety in numbers from predators without requiring complex social cooperation.
Gathering on Land for Reproduction and Rest
The most conspicuous examples of seals forming large groups occur on land or ice for specific biological necessities. These dense, temporary gatherings are known as “rookeries” during the breeding season. Species like elephant seals form massive colonies where one dominant male defends a large group of females, creating a highly structured, polygamous social hierarchy. This density is driven by the limited availability of suitable breeding habitat.
During the pupping season, females congregate to give birth and nurse their single pup. This period sees intense competition among females for prime pupping sites and among males for access to mates. Colonies are also utilized for the annual molting process, requiring seals to remain on land for an extended period, sometimes for two to three weeks, while shedding their old fur and skin. Hauling out is a response to a physiological or reproductive need rather than a desire for constant companionship.
Hunting and Migration Behavior in Water
When seals are actively traveling or foraging, their behavior is typically less social than their activities on land. Migration often involves individual seals traveling alone, sometimes covering thousands of kilometers between feeding grounds and breeding sites. Northern fur seals, for example, undertake massive migrations where individuals may travel alone for months, sometimes covering up to 6,000 miles annually.
Seals moving between locations may appear to be traveling in a loose group because they are following the same concentrated food source or using the same migratory corridor. Recent observations of harbor seals have noted mass gatherings in the water, suggesting they may occasionally engage in group foraging to corner fish. Even in long-distance migrations, such as those undertaken by female Northern elephant seals, their movements show coherence in direction. This suggests they are influenced by similar oceanographic cues, resulting in regional aggregations without coordinated, cooperative travel.