Hippopotamuses are massive, semi-aquatic mammals commonly found in the rivers and lakes of sub-Saharan Africa. These imposing creatures, known for their barrel-shaped bodies, spend much of their day submerged. Their aquatic lifestyle raises questions about how they navigate water and their speeds. Understanding their unique relationship with water reveals fascinating insights into their movement.
Understanding Hippo Aquatic Movement
Hippos navigate aquatic environments distinctively, as they don’t truly “swim” conventionally. Unlike many aquatic mammals, hippos primarily move by bounding or walking along the riverbed. Their dense bone structure and substantial weight prevent them from floating, allowing them to sink and walk underwater. This locomotion enables surprising underwater speeds, up to 5 miles per hour (8 kilometers per hour). When in deeper sections of water, they push off the bottom with powerful thrusts, creating a porpoise-like leap that gives the illusion of swimming.
Hippos control buoyancy by adjusting breath and posture, precisely regulating their position in water. Adult hippos can hold their breath for up to five minutes while submerged, well-suited for shallow river habitats. Young hippos surface more frequently, every 30 to 60 seconds. They can even sleep underwater, instinctively rising to the surface for air without waking.
Built for the Water: Hippo Adaptations
Hippos possess adaptations that make them efficient in their aquatic surroundings. Their bones are notably dense, known as osteosclerosis, which contributes to their negative buoyancy, allowing them to sink effortlessly to the riverbed. This density enables them to maintain contact with the bottom, providing a stable platform for their powerful legs to push off and propel them forward. Their short, stout legs provide robust propulsion through the water, allowing for their characteristic underwater gallop.
Their feet exhibit features beneficial for aquatic movement, including four webbed toes that help distribute their immense weight and provide thrust. The placement of their sensory organs is uniquely suited for their semi-aquatic lifestyle. Their eyes, ears, and nostrils are positioned high on top of their heads, enabling them to remain almost entirely submerged while seeing, hearing, and breathing above the water’s surface. When fully underwater, hippos can close their nostrils and ears to prevent water entry. They also have a clear membrane, sometimes called “built-in goggles,” that covers their eyes, protecting them while allowing underwater vision.