Rats, like all mammals, cannot breathe underwater. Despite their adaptability to diverse environments, including those near water, they lack the specialized biological structures for aquatic respiration. This common misconception often arises from their observed resilience and presence in places like sewers.
Why Rats Cannot Breathe Underwater
Rats possess lungs, similar to humans, designed exclusively for air. These lungs function by facilitating gas exchange, where oxygen from the air is absorbed into the bloodstream and carbon dioxide is released. When submerged, water fills the respiratory passages and lungs, preventing this vital exchange of gases. Without access to atmospheric oxygen, the rat’s body cannot sustain its metabolic processes, leading to respiratory failure. The intricate network of airways within their lungs is adapted for gaseous environments, not liquid.
How Rats Navigate and Survive in Water
Despite their inability to breathe underwater, rats are surprisingly proficient swimmers and can navigate aquatic environments for limited periods. They possess strong legs that propel them through water and a streamlined body that reduces drag. Their long tails also serve as a rudder, aiding in steering and balance during swimming.
Rats can hold their breath for a significant, though constrained, duration, typically up to three minutes. In some instances, particularly when distressed, this breath-holding capacity can be shorter, around 10 to 20 seconds. Their dense, water-repellent fur can trap a layer of air close to their skin, which provides additional buoyancy and insulation in cold water.
These aquatic abilities are primarily used for temporary navigation, such as escaping predators, foraging for food, or traversing flooded areas, rather than for prolonged aquatic living. Rats have even been observed treading water for extended periods, sometimes up to 72 hours, demonstrating their impressive stamina.
Consequences of Prolonged Submersion
If a rat remains submerged beyond its breath-holding capacity, severe physiological consequences quickly ensue. The body experiences a rapid depletion of oxygen, leading to a condition known as hypoxia. As oxygen levels fall, the rat’s body attempts to conserve its remaining oxygen through a mammalian diving reflex.
This reflex involves slowing the heart rate, ceasing breathing, and constricting blood vessels to prioritize blood flow to vital organs like the brain and heart. However, these protective mechanisms are temporary.
Once the stored oxygen is exhausted, the rat will involuntarily inhale water. This inhalation causes damage to the lungs and disrupts the body’s electrolyte balance, ultimately leading to drowning. The ultimate outcome of prolonged submersion without access to air is fatal, highlighting their complete dependence on atmospheric oxygen for survival.