Seals, marine mammals known as pinnipeds, are defined by their semi-aquatic existence and ability to spend time on land. This behavior, called “hauling out,” involves coming ashore onto beaches, rocks, or ice floes for necessary terrestrial activities. While seals are adapted for life in the ocean, their time on land is governed by biological needs and physical limitations. The duration of their stay is highly variable, ranging from a few hours to several weeks, depending on the purpose of the haul-out and the specific species.
Physiological Constraints on Land
The primary factors limiting a seal’s time ashore are managing body temperature and conserving moisture. The thick layer of blubber that insulates them in cold water becomes a liability on land, making heat dissipation difficult and creating a high risk of overheating (hyperthermia). Seals cope by exposing their flippers, which act as “thermal windows” to release excess heat, or by flipping cool sand or mud onto their bodies.
If the ambient temperature exceeds 30°C, some species are compelled to return to the water. Dehydration is also a constraint, as seals do not drink freshwater and must rely on metabolic water conservation. Specialized species, like the elephant seal, have a unique nasal structure that helps recycle moisture in their breath, significantly reducing water loss during long fasts.
Duration Based on Hauling Out Purpose
The length of time a seal remains on land is directly tied to the specific biological function it needs to perform. For common activities like resting, grooming, or digesting a meal, seals may haul out for a few hours up to a full day or two. This short-term rest allows them to recover from dives, conserve energy, and prepare to return to the water to forage.
Extended stays are required for major life events, such as molting, the annual process of shedding their old coat. During molting, which can last up to 6 to 8 weeks for grey seals, the seal must remain dry for the new coat to grow properly, forcing them to fast and stay immobile. The longest terrestrial durations occur during the breeding and pupping seasons. Female elephant seals fast and remain on land for up to 28 days while nursing their pups. Male grey seals are known to fast for over 50 days to defend their territory during the mating season, subsisting entirely on blubber reserves.
Differences Between True Seals and Sea Lions
The term “seal” is used broadly, but significant anatomical differences exist between true seals (Phocidae) and sea lions/fur seals (Otariidae) that affect their terrestrial mobility. True seals lack external ear flaps and cannot rotate their hind flippers underneath the body. This physical limitation means they move on land through a cumbersome, caterpillar-like motion called “galumphing,” making them relatively slow.
Sea lions and fur seals, known as “eared seals,” have visible external ear flaps. Their key terrestrial advantage is the ability to rotate their hind flippers forward, allowing them to walk or even gallop on all four limbs. This superior mobility means Otariids are better adapted to spend longer, more active periods on terrestrial rookeries.