Hippos, those colossal creatures often seen partially submerged in African waterways, possess a unique relationship with water that often leads to misunderstandings about their aquatic abilities. Despite their common depiction, these massive mammals do not “swim” in the conventional sense that many other aquatic animals do. Instead, their movement in water is a fascinating display of specialized adaptations, allowing them to navigate their watery environments with surprising agility.
How Hippos Navigate Water
Hippos move through water not by floating and propelling themselves with rhythmic limb strokes, but by using a distinctive method of walking or bounding along the bottom of rivers and lakes. Their dense bone structure allows them to sink and maintain contact with the riverbed, acting like ballast. This enables them to effectively “run” or “gallop” underwater, pushing off the ground with their powerful legs. In deeper sections, they perform porpoise-like leaps, pushing off the bottom to move forward and surface for air.
Hippos can achieve speeds of up to 5 miles per hour (8 kilometers per hour) underwater through this bottom-walking technique. They can hold their breath for extended periods, typically around five minutes, which facilitates their submerged movements and allows them to remain hidden. While adults can stay submerged for several minutes, calves need to surface more frequently, usually every 40 seconds to two minutes.
Why Hippos Rely on Water
Water is important for hippos, serving several functions. They spend the majority of their daylight hours, often up to 16 hours, submerged in water to manage their body temperature in the hot African climate. Their sensitive skin, which lacks sweat glands, is highly susceptible to sunburn and dehydration when exposed to direct sunlight for prolonged periods. Submersion provides a continuous cooling effect and prevents their skin from drying out and cracking.
Water also offers protection from predators, especially for calves. Hippos typically emerge from the water after dusk to graze on land, returning to the water before the sun’s heat becomes too intense. This routine conserves energy, as their large bodies are buoyed by the water, reducing the physical effort required to support their weight.
Remarkable Aquatic Adaptations
Hippos possess several physical characteristics that make them well-suited for their semi-aquatic existence. Their eyes, ears, and nostrils are positioned on top of their heads, allowing them to see, hear, and breathe while the rest of their massive bodies remain submerged. When fully diving underwater, they can instinctively close their nostrils and ears to prevent water from entering. Their eyes are also equipped with a clear membrane that acts like goggles, providing protection while still allowing them to see underwater.
Their skin glands secrete a fluid often referred to as “blood sweat.” This reddish-orange, oily fluid is not actual blood or sweat but contains two acidic pigments. This natural secretion acts as a sunscreen and also functions as an antiseptic, helping to prevent infections in their skin.