Marine Mammal Adaptations
Generally, marine mammal lungs are proportionately smaller than humans', but they:
- Use oxygen more efficiently. They fill their lungs and exchange 90% of their air in each breath, have high blood volume, and their blood chemistry allows greater oxygen retention (the high red blood cell count and increased myoglobin make their muscle tissue and blood dark red).
- Have a high tolerance to lactic acid and carbon dioxide. Their muscles can work anaerobically (without oxygen) while they hold their breath.
- Can tolerate tremendous atmospheric pressure at great depths. Lungs and ribs are collapsible, air spaces are minimized, and nitrogen absorption is limited.
- Drag is reduced by hydrodynamic body forms.
- Appendages are modified for maximal propulsion and minimal drag.
- A large body with small surface-to-volume ratio reduces heat loss. Blubber or thick underfur is used as insulation.
- Complex circulatory system in extremities is used to conserve and dissipate heat.
- Young pinnipeds and cetaceans grow fast on milk with 40–50% fat (human milk is 3.3% fat).
Most marine mammals rarely drink fresh water; instead, they:
- Utilize water present in their food, inspired air, and blubber.
- Have specialized kidneys that produce urine that is saltier than seawater.
- Marine mammals communicate underwater with sound, and many species use sound (echolocation) to locate prey. Tactile senses are acute. Pinnipeds and fissipeds have well-developed facial whiskers.