Many mammals instinctively navigate aquatic environments with ease, but some species exhibit a surprising inability to swim. This contrasts with the general perception that swimming is a universal mammalian trait. While most mammals can propel themselves through water, a select few are remarkably unsuited for it.
Unexpected Non-Swimmers
Among mammals surprisingly unable to swim are giraffes, hippopotamuses, and most great apes, including chimpanzees and gorillas. Giraffes, despite their towering stature, are not adept in water; their body structure makes efficient swimming challenging. Hippopotamuses spend extensive time in water, but do not truly swim. Their dense bones and heavy bodies cause them to sink, moving instead by walking or galloping along the riverbed. Great apes generally lack the natural instinct and physical characteristics for swimming, with deep water often serving as a habitat barrier.
While some sources debate if camels can swim, most are not typically found in aquatic environments and are not adapted for swimming. Armadillos, despite their heavy shells, can cross water by holding their breath and walking underwater. These examples defy the common assumption that all mammals possess an inherent swimming ability.
Physical and Behavioral Limitations
The inability of certain mammals to swim stems from physical characteristics and behavioral predispositions. For giraffes, their unique anatomy, including long legs and a high center of gravity, makes maintaining stability and propulsion in water difficult. Their disproportionately long forelimbs and heavy shoulders make swimming strenuous, requiring them to hold their heads at an uncomfortable angle to keep their nostrils clear. The sheer drag created by their long limbs further impedes efficient movement.
Hippopotamuses, despite their aquatic lifestyle, possess bones denser than water, preventing natural floating. Their bodies are designed for walking on land or pushing off the bottom of a water body. Great apes’ dense body composition and low body fat contribute to a lack of natural buoyancy, causing them to sink. They often exhibit an aversion or fear of deep water, and a lack of instinctive dog-paddling movements makes swimming unnatural and dangerous for them.
Survival Without Swimming
Mammals that cannot swim have evolved alternative survival strategies. Giraffes typically inhabit savannas and open woodlands, where large, deep water bodies are less common or can be avoided. They obtain most of their water from the plants they consume, reducing reliance on direct water sources. When they need to drink, they adopt an awkward splayed-leg stance, demonstrating their adaptation to terrestrial hydration.
Hippopotamuses thrive in aquatic environments by leveraging their body density to walk or gallop along riverbeds. Their skin requires constant moisture to prevent dehydration, and staying submerged offers protection from the sun and predators. Great apes, such as chimpanzees and bonobos, often live in forested areas where rivers act as natural boundaries. Their arboreal lifestyle and ability to navigate dense vegetation reduces the necessity of aquatic travel.