Dolphins, despite being mammals that breathe air, are not equipped to survive on land for any significant duration. Their entire physiological makeup is adapted for an aquatic existence, making them vulnerable and unable to breathe effectively outside of water. While they possess lungs and inhale oxygen from the atmosphere, their bodies cannot withstand the terrestrial environment.
The Aquatic Respiratory System of Dolphins
Dolphins, like all marine mammals, breathe air into their lungs, unlike fish that use gills to extract oxygen from water. Their breathing is a conscious, voluntary process, unlike the automatic breathing in humans. To take a breath, a dolphin surfaces, and its blowhole, located on top of its head, opens. This allows them to quickly exhale and inhale before submerging again.
Dolphin lungs are highly efficient, exchanging 80% to 90% of their air with each breath, a stark contrast to the 10-15% exchanged by humans. This efficiency, along with adaptations like higher concentrations of oxygen-storing proteins (hemoglobin and myoglobin), enables dolphins to hold their breath for extended periods, typically 8 to 10 minutes. A diving reflex also slows their heart rate and redirects blood flow to vital organs, conserving oxygen during dives.
Why Land Poses a Threat to Dolphins
The adaptations that allow dolphins to thrive in water become liabilities on land. Without the buoyant support of water, their heavy bodies are subjected to gravity. This pressure can cause internal organs, particularly lungs, to collapse under their own weight, making breathing difficult and leading to suffocation.
Dolphin skin, designed for a wet environment, is susceptible to desiccation. Exposed to air, their skin dries out, cracks, and can lead to dehydration and infection. Dolphins also possess a thick blubber layer, which provides insulation in cold water. On land, this blubber becomes a disadvantage, causing rapid overheating as they cannot dissipate heat. Their streamlined bodies and lack of limbs also mean they are immobile on land, unable to move or escape danger.
Stranding and Survival Limitations
When a dolphin strands, the consequences of these physiological challenges become dire. The collapse of their lungs under gravity can lead to suffocation, and without water, they face rapid dehydration and severe sunburn. Overheating is also a threat due to their insulating blubber and inability to regulate temperature.
The time a dolphin can survive out of water is limited, often a few hours, depending on factors like size, weather conditions, and internal organ damage. Human intervention is crucial in stranding events to provide supportive care, such as keeping the animal cool and moist, and to attempt rescue. Even with prompt assistance, the prognosis for stranded dolphins without immediate return to water is grave.