ほとんどの哺乳類は、陸生動物であるため、海に住むことに適応していません。つまり、陸上に住んでいます。彼らは、空気を呼吸したり、発汗や喘ぎを通して体温を調節したり、手足で土地を簡単に動かすなど、土地に住むことを可能にする適応を持っています。対照的に、クジラ、イルカ、アザラシなどの海洋哺乳類には、長時間息を止め、肥大で体を隔離し、フリッパーや尾で効率的に泳ぐ能力など、海に住むことができる適応があります。。また、海洋環境は、圧力の変化、淡水の不足、異なる食物連鎖などの要因により、哺乳類にとっても困難です。
Most mammals are not adapted to living in the ocean because they are terrestrial animals, meaning they live on land. They have adaptations that allow them to live on land such as the ability to breathe air, regulate their body temperature through sweating or panting, and move easily on land with their limbs. In contrast, marine mammals such as whales, dolphins, and seals have adaptations that allow them to live in the ocean such as the ability to hold their breath for long periods of time, insulate their bodies with blubber, and swim efficiently with flippers or tails. The ocean environment is also challenging for mammals due to factors such as pressure changes, lack of fresh water, and a different food chain.