The leopard seal (Hydrurga leptonyx) is a massive and formidable predator of the Antarctic and Southern Ocean. These large true seals spend the majority of their lives in the frigid waters and on the surrounding ice floes of the pack ice zone. They are built for a life of hunting in the water, which raises questions about their movement capabilities when they haul themselves onto solid ground. Understanding their terrestrial speed reveals the limits of a body highly specialized for the marine environment.
Measured Speed on Terrestrial Surfaces
Movement on land or ice is not a sustained activity for the leopard seal, and their speed varies significantly based on their motivation. When moving casually—such as shifting a resting position or briefly crossing a patch of snow—their speed is generally slow and labored. This relaxed pace often falls below two miles per hour, resembling a slow human walking speed. Accurate measurement of a leopard seal’s maximum burst speed on ice is difficult because their terrestrial movements are unpredictable and short-lived. Observations suggest they can achieve a much higher, though unsustainable, speed when highly motivated, but this is always a brief sprint.
Unique Locomotion Style
The leopard seal belongs to the “true seal” family, meaning it lacks the ability to rotate its pelvic bones forward for walking, unlike sea lions. This anatomical constraint forces them to use a unique and physically demanding method of terrestrial locomotion known as “galloping” or undulation. The movement involves a synchronized arching and straightening of the spine, propelling the body forward in a caterpillar-like motion.
The massive fore-flippers, which are highly developed for swimming, are used to anchor and pull the body along the surface. These flippers provide the necessary traction and power for forward momentum and steering on rougher surfaces. Conversely, the small hind flippers are largely useless for propulsion on land and are typically dragged behind the body.
The type of surface dictates the efficiency of this locomotion style. On rough or rocky terrain, the movement is slow and strenuous, requiring great effort to lift and push the heavy body. However, on smooth, slick ice or snow, they can use their streamlined bodies to their advantage, sometimes tobogganing or sliding to cover distance more easily. Even with this adaptation, their movement on land remains awkward and inefficient compared to their performance in the water.
Aquatic Speed Versus Land Movement
The leopard seal is an apex predator in the water, with a body structure optimized for speed and agility beneath the surface. Their long, serpent-like, and muscular bodies are perfectly hydrodynamic, allowing them to slice through the water with minimal drag. They are capable of sustained cruising speeds and can reach burst speeds of up to 25 miles per hour (40 kilometers per hour) when pursuing prey. Their powerful swimming is driven primarily by the large, paddle-like fore-flippers, which act as hydrofoils to generate propulsion.
This efficiency in water is a consequence of millions of years of evolution for an aquatic lifestyle. These same adaptations, however, cause their clumsiness on land. Their movements on ice or land are a necessary inconvenience, used only for short periods to rest, breed, or thermoregulate, before returning to their true element.