Table of Contents (click to expand)The Evolution Of WhalesWhales And Dolphins Don’t Have GillsHow Do Whales Hold Their Breath Underwater For So Long? Whales and dolphins can hold their breath for so long underwater because they have efficient respiratory systems, they can conserve energy underwater by purposely slowing their heart rate, constructing select arteries and limiting blood supply to only a few organs, and they have a protein in their muscles called myoglobin that stores oxygen. Here’s a fun fact: whales and dolphins are not really fish. This might be one of those truths of the world that make you … Continue reading How Can Whales And Dolphins Hold Their Breath For So Long Underwater?