Time Seals Spend on Land
Seals, as marine mammals, spend a significant portion of their lives within aquatic environments; however, they regularly come ashore for various essential activities. One primary reason seals haul out is for rest, allowing them to conserve energy and digest their meals safely. Many species also utilize land for pupping, where females give birth and nurse their young for several weeks, providing a safe nursery.
Additionally, seals undergo an annual molting process, shedding their old fur and growing new coats, which often requires them to remain on land for extended periods. During this time, energy is redirected from foraging to fur growth, making terrestrial resting beneficial. Coming ashore also provides an escape from aquatic predators, such as killer whales and large sharks. These terrestrial excursions are temporary, serving as a necessary interlude in their predominantly marine existence.
Specialized Biological Adaptations
Seals possess a suite of specialized biological adaptations for both their aquatic and terrestrial environments. Their streamlined, torpedo-shaped bodies minimize drag in water, allowing for efficient swimming through powerful undulations of their hindquarters and strong strokes of their hind flippers.
These flippers, while highly effective for propulsion in water, are also modified for limited terrestrial locomotion, enabling a somewhat awkward but effective movement across land through a “galloping” or “caterpillar-like” motion. Their fore-flippers, equipped with strong claws, aid in maneuvering on various surfaces.
A thick layer of blubber beneath their skin serves multiple purposes, primarily providing insulation against the cold ocean waters. This blubber also acts as an energy reserve, sustaining them during periods of fasting, such as during molting or pupping seasons. On land, blubber helps regulate body temperature by dissipating excess heat, preventing overheating. Their dense fur also contributes to insulation, trapping a layer of air against the skin to reduce heat loss in water and providing some protection on land.
The Indispensable Role of Water for Seals
Despite their adaptations for terrestrial excursions, water plays an indispensable role in the long-term survival of seals. Their primary food sources, including fish, squid, and crustaceans, are found exclusively within marine environments, necessitating regular returns to the water for hunting and foraging. Seals obtain almost all their necessary hydration from the metabolic breakdown of fats in their prey and the water content within the prey itself, rather than by drinking seawater, which would lead to dehydration due to its high salt content.
Water is also crucial for temperature regulation, especially for cooling down. While blubber insulates them in cold water, seals can overheat on land, particularly in warmer climates or during strenuous activity. Returning to the water allows them to dissipate excess body heat efficiently and avoid hyperthermia.
The ocean additionally provides a critical refuge from terrestrial predators, such as polar bears in Arctic regions or coyotes and wolves in some coastal habitats. Prolonged absence from water would lead to severe dehydration, an inability to forage for food, and an increased risk of overheating.