The kangaroo is an iconic Australian marsupial recognized globally for its powerful bipedal hopping, driven by large, synchronized hind limbs and a muscular tail. Despite being primarily land animals, their relationship with water—specifically their ability to swim and their susceptibility to drowning—is often overlooked. The physical adaptations that make them supreme hoppers necessitate a drastic shift in mechanics when they enter an aquatic environment. Understanding this shift reveals a surprising versatility in an animal widely considered a creature of the open plains.
Why Kangaroos Enter the Water
Kangaroos interact with water bodies for several practical and defensive reasons related to their survival in the Australian environment. One frequent motivation is thermoregulation, particularly for large red and grey kangaroos living in hot, arid climates. Submerging their bodies in a dam or river offers an immediate and effective way to dissipate excess heat, a behavior commonly observed during the peak warmth of the day.
Necessity also drives them into water, especially when natural obstacles like rivers or flooded areas must be crossed to access foraging grounds or escape bushfires. Environmental pressures sometimes leave them with few options other than swimming. However, the most common reason for a kangaroo entering the water is as a defensive strategy against predators.
When pursued by a predator, such as a dingo or a domestic dog, a kangaroo may retreat into a body of water deep enough for it to stand but force the attacker to swim. This maneuver instantly negates the attacker’s speed advantage on land and alters the dynamic of the confrontation entirely. By standing upright in the water, the marsupial can leverage its size and powerful forearms, placing it in a superior defensive position.
The Mechanics of Kangaroo Swimming
When a kangaroo enters deep water, its terrestrial bipedal hopping gait is abandoned in favor of a quasi-quadrupedal swimming action. The powerful hind legs, synchronized for movement on land, begin to operate independently, alternating in a motion resembling a dog-paddle. This shift from a two-limbed to a four-limbed propulsion system is a remarkable display of locomotor plasticity.
The smaller forelimbs play a substantial role in propulsion. These arms perform an alternating posterior power stroke, pushing water backward to generate forward momentum. The forelimb movement is similar to that of a human performing the Australian crawl, contributing to the animal’s overall speed and direction.
The large, muscular tail, which acts as a balancing fifth limb while hopping, is repurposed in the water. While not the primary source of propulsion, it functions effectively as a rudder and stabilizer. By subtly adjusting the tail’s position, the kangaroo maintains balance and steers its body through the water.
Vulnerability and Drowning Risks
Despite their ability to swim, kangaroos are not specialized aquatic mammals, and they face risks of drowning under certain circumstances. Their dense musculature, especially in the hindquarters, makes maintaining buoyancy a challenge over extended periods. A sustained swim, perhaps over hundreds of meters or against a strong current, can lead to muscle fatigue and exhaustion, increasing the probability of submersion.
A frequent source of accidental drowning occurs when a kangaroo cannot easily exit the water. Many man-made dams, steep-sided water tanks, or natural banks are slippery or too high for the animals to climb out of once they are waterlogged. The large hind legs, adapted for explosive upward and forward movement on land, are poorly suited for climbing steep, muddy inclines from a deep-water position.
Kangaroos also intentionally utilize water to cause drowning as a defensive tactic against perceived threats. When a predator like a dog pursues a kangaroo into deep water, the marsupial gains a leverage advantage by standing on the bottom. The kangaroo can then use its strong forearms to hold the swimming predator’s head underwater. While kangaroos can drown due to exhaustion or entrapment, they also use the aquatic environment to deliberately drown other animals.