Manatees are large, gentle aquatic mammals, often referred to as “sea cows.” These herbivores are fully adapted to life underwater, yet they maintain a fundamental connection to the air above the surface. As mammals, they must breathe air to survive. Their unique breathing patterns and specialized physiology allow them to thrive in their aquatic environments.
Manatee Respiratory Needs
Manatees, unlike fish, do not possess gills; instead, they rely on lungs to extract oxygen directly from the atmosphere. They must regularly surface to inhale air. Their aquatic lifestyle, despite requiring atmospheric oxygen, highlights their adaptation to a watery habitat.
Breathing Frequency and Duration
The frequency with which manatees surface for air varies significantly depending on their activity level. When actively swimming, feeding, or moving, a manatee may need to surface as often as every 30 seconds to a few minutes. In contrast, when resting or sleeping, they can hold their breath for considerably longer periods. A resting manatee can remain submerged for up to 20 minutes before needing to resurface for air. This ability to extend breath-holding times allows for energy conservation.
Physiological Adaptations for Diving
Manatees possess several physiological adaptations that enable their breath-holding capabilities. Their lungs are flattened and elongated, extending horizontally along much of their back, which aids in buoyancy control. These lungs allow for efficient gas exchange; manatees can renew approximately 90% of the air in their lungs with each breath, compared to humans who typically exchange about 10%. This maximizes oxygen intake.
Their respiratory muscle structure includes two separate hemi-diaphragms, allowing for independent air exchange in each lung. During dives, manatees also exhibit bradycardia, a slowing of their heart rate, which reduces the body’s overall oxygen demand. Blood flow is shunted away from less oxygen-sensitive areas and redirected towards the brain and heart, preserving oxygen for these organs.
Another adaptation is their dense bone structure. Manatee bones, particularly their ribs, are solid and lack a marrow cavity, making them very heavy. This increased bone density acts as a natural ballast, helping manatees sink and remain submerged on the seabed with minimal effort while resting. The combination of these specialized lungs, circulatory adjustments, and heavy bones allows manatees to efficiently manage their time above and below the water’s surface.