Swimming is an important survival skill for many animals, allowing them to find food, avoid predators, and traverse their environments. However, not all animals are equipped for aquatic locomotion. There are a number of land mammals, birds, insects, and other creatures that cannot swim at all or are very poor swimmers. Understanding why some animals can’t swim gives insight into the evolutionary adaptations and constraints that have shaped different species.
Mammals That Cannot Swim
Most mammals have at least some ability to swim. Their buoyancy, fur, and ability to dog paddle gives them basic swimming skills. However, there are exceptions, particularly among domesticated and terrestrial species that have lost their aquatic adaptations.
Dogs
Dogs are often considered poor swimmers, though some breeds like Labrador Retrievers are quite skilled in the water. The physical attributes and behaviors that make dogs ill-equipped for swimming include:
- Lack of webbing between toes
- Poor buoyancy due to lack of body fat
- Top-heavy bodies and disproportionately large heads
- Tendency to panic and thrash in water
Certain dog breeds have particular difficulties swimming due to their body shape. For example, Bulldogs have dense, muscular bodies and large heads that cause them to quickly sink. Short-muzzled dogs like Pugs, Boxers, and Shih Tzus cannot keep their nose above water well due to the shape of their faces.
Cats
Though cats are agile and have some ability to swim, most domestic cats are not fond of water and are not especially skilled swimmers compared to other mammal species. Reasons cats tend to avoid water and swim poorly include:
- Dislike of getting fur wet
- Instinct to avoid water due to lack of exposure during kittenhood
- Lack of webbing between toes
- Long fur that weighs down the body
- Aversion to the loss of control and vulnerable feeling of swimming
The Turkish Van is one breed of cat known for its unusual fondness for water. Their water-repellent coat and webbed toes make them adept swimmers compared to other cats.
Primates
Our closest primate relatives also lack innate swimming skills. Great apes like gorillas, chimpanzees, bonobos, and orangutans cannot swim at all and quickly sink in deep water. Their heavy bodies, long limbs, and lack of adaptations for swimming make them unsuited for aquatic mobility. Their aversion to water also has an instinctual basis in their arboreal ancestry.
Rodents
The vast majority of rodents are also incapable of swimming. Their small limbs are not equipped with webbed feet or other anatomical features to aid swimming. Buoyancy and body shape also work against them. Hamsters, gerbils, chinchillas, degus, and other popular pet rodents will quickly drown if immersed in water, as will wild species like mice, voles, lemmings, and porcupines.
Rabbits
Rabbits are another mammal that lacks any natural swimming ability. Their fur becomes waterlogged, weighing them down. They also have a high metabolism and limited fat stores that mean they quickly become exhausted and hypothermic in water. Panicked thrashing to get out of the water can cause rabbits to take in water and drown.
Birds That Sink Like Stones
While most birds have some ability to float and paddle in water, there are certain species that are especially unsuited for swimming. Some of the birds that sink like stones when they land in water include:
Ostriches
The largest extant birds in the world, ostriches cannot fly and also cannot swim. Their long, powerful legs are great for running, but paddle uselessly when submerged. Their feathers also quickly become waterlogged.
Cassowaries
Cassowaries are another large, flightless bird that will sink and drown if they find themselves in deep water. They live in wet tropical forests, but avoid entering pools, streams, and other bodies of water.
Parrots
The dense plumage and small wings of parrots make swimming impossible. All parrot species will sink and drown if they cannot get out of the water almost immediately.
Chickens
Despite having wings, chickens are terrible swimmers. Their feathers lack the oily waterproof coating found in ducks and other waterfowl. Once their plumage becomes soaked, they have no buoyancy and sink. Their short wings also don’t provide thrust for swimming when submerged.
Peacocks
The elaborate plumage of peacocks may be splendid for courtship, but it quickly weighs them down in water. Peacocks can flap their wings to gain some propulsion across the surface, but they cannot stay afloat for more than a moment or two.
Emus
Emus are large, flightless birds that live in Australia. If they happen to fall into a pond or trough, they thrash wildly but cannot stay above the surface. Their plumage absorbs water rapidly, negating any buoyancy.
Rheas
Rheas are related to ostriches but live in South America. They also cannot fly or swim. Their feathered wings are vestigial, providing no help staying afloat if they become submerged.
Penguins
Penguins may seem like obvious swimmers given their aquatic lifestyle. However, penguins rely on their dense bones and streamlined shape to “fly” through the water. If removed from the water, their feathers quickly become waterlogged and they have difficulty moving on land. Though they live at sea, they would drown if unable to get back to land or ice.
Insects and Arachnids That Sink
Insects and arachnids have an exoskeleton that tends to become waterlogged, causing them to sink rapidly in water. Just a few of the bugs that cannot swim include:
Spiders
All spiders quickly become trapped and drown in water. Though some spiders can skim across the surface of pools and puddles, their light weight and hydrophobic hairs quickly become useless if submerged.
Beetles
Beetles have heavy exoskeletons and limbs not designed for swimming. While whirligig beetles can row in circles on the water’s surface, most beetles immediately sink if they fall into water.
Grasshoppers
The powerful hind legs of grasshoppers let them leap incredible distances on land, but are useless for swimming. Grasshoppers sink as soon as they hit water.
Cockroaches
Cockroaches prefer dark, moist habitats but are not adapted for life underwater. They quickly become trapped and drown if immersed.
Ants
Ants are adept at navigating their terrestrial world but cannot swim at all. Fire ants use their mandibles and legs to form rafts for survival if floods cover their nests. Other ants simply sink and drown if plunged into water for more than a few seconds.
Flies
True flies like house flies have short life spans and no need to ever enter water. They skitter across the surface with water-repellent hairs but soon become trapped if they fall in.
Butterflies
Butterflies begin life as caterpillars that may cross small pools and streams. However, the adult insects have no ability to swim and will quickly become disabled if their wings get wet.
Moths
Like butterflies, most moths have wings covered in fine scales that render them useless for flight if they get wet. Moths cannot swim and will sink and drown rapidly in water.
Stick insects
Stick insects have elongate bodies and spindly legs perfect for resembling vegetation. However, these adaptations make them helpless in water. They have no defense against drowning if submerged.
The Importance of Swimming Adaptations
Most animals have evolved adaptations that allow them to swim to some degree. However, there are some species that simply lack those aquatic adaptations. Their morphology and instincts are designed for terrestrial life.
Animals that cannot swim effectively tend to have:
- Lack of webbed feet or other limbs adapted for paddling
- Poor waterproofing on feathers or fur
- Heavy bodies with little fat or air-filled bones for buoyancy
- Instinctual aversion to water or fear of drowning
For animals adapted to drier regions, swimming would provide little selective advantage. However, falling into water can be deadly for them. Understanding what makes some animals sink rather than swim provides insight into evolutionary constraints and trade-offs that shape survival in different habitats.
Conclusion
While most animals can swim to some degree, certain groups like terrestrial mammals, large flightless birds, insects, and arachnids lack adaptations for swimming. Traits like waterlogged fur and feathers, heavy bodies, inefficient limbs for paddling, and fear of water cause them to sink. Swimming requires specific morphological and behavioral adaptations that terrestrial animals simply do not possess. Knowing what animals cannot swim helps illustrate how evolution equips different species for survival in either aquatic or drier habitats.