Seals, a diverse group of marine mammals known as pinnipeds, spend significant portions of their lives in the ocean but are also frequently observed on land or ice. While fundamentally adapted for aquatic environments, their ability to navigate terrestrial landscapes is a necessary aspect of their life cycle. Their presence ashore serves various specific purposes, allowing them to thrive across two distinct habitats.
Their Primary Aquatic Habitat
Seals are primarily creatures of the water, where they perform most essential activities, including hunting and feeding. Their bodies are highly specialized for marine environments. A streamlined, torpedo-shaped body minimizes drag, allowing for agile and swift movements.
Their powerful flippers are designed for aquatic propulsion. Some seal species use large fore-flippers to “fly” through the water, while others propel themselves using strong, side-to-side movements of their hind flippers. The ocean is their main living space, where they spend the majority of their time.
Reasons Seals Come Ashore
Seals come ashore for several specific and temporary reasons, a behavior known as “hauling out.” One primary motivation is breeding, which includes giving birth to pups and mating. Females often return to familiar land or ice locations to deliver and nurse their young, forming large colonies during this sensitive period.
Another important reason is molting, the annual process of shedding old fur and replacing it with a new coat. During this time, seals often remain on land because increased blood flow to the skin is needed for new hair growth, making staying in cold water energetically costly. Seals also haul out to rest, conserve energy, or warm themselves in the sun, a process known as thermoregulation. Additionally, coming ashore can offer a temporary refuge from aquatic predators such as sharks or killer whales.
Physical Adaptations for Dual Life
Seals possess several physical adaptations for their amphibious lifestyle. A thick layer of blubber beneath their skin provides insulation against cold water, maintaining core body temperature. This blubber also serves as an energy reserve, especially during fasting periods on land, and contributes to their buoyancy.
Their flippers, optimized for swimming, also facilitate limited movement on land. Seals can hold their breath for remarkable durations, from 15 minutes to over an hour for some species, due to adaptations like increased oxygen storage in their blood and muscles and a reduced heart rate during dives. Their thick fur offers some protection.
How Different Seals Move on Land
Seals move on land differently depending on their group: true seals (phocids) or eared seals (otariids), which include sea lions and fur seals. True seals have small front flippers and cannot rotate their hind flippers forward under their bodies. This means they move on land by undulating their bodies in a caterpillar-like motion, often described as “humping” or “flopping.”
In contrast, eared seals possess larger front flippers and can rotate their hind flippers forward. This allows them to support their weight and “walk” on all fours, making them more agile and capable of faster movement on terrestrial surfaces.