Of all the living reptiles, the 12 modern crocodile (Crocodylus spp.) species are the largest. Like all reptiles, crocodiles breathe with lungs rather than gills. Lungs are evolution’s solution to respiration issues faced by the first lower life forms that tentatively crept out of the water to eventually live on land full time. It became necessary for these animals to take their oxygen from the atmosphere rather than from the water.
A crocodile can dive beneath the water’s surface and hold his breath for extended periods of time. The smaller the croc, the less time he can spend underwater. During a voluntary dive, such as when hunting underwater, the crocodile can remain submerged for 10 to 15 minutes. If a perceived threat prompts the animal to dive involuntarily, the underwater time may be 30 minutes or longer. In dire emergency situations, most crocodiles can stay under for up to two hours. During such an extreme dive, the heart rate may drop drastically to only two or three beats every minute in a desperate bid to conserve oxygen.
Crocodiles are fast, stealthy and highly maneuverable due to powerful pelvic, rib, diaphragm and abdominal muscles that move their lungs as needed within the body. The animal pulls these muscles backward to dive, pushes them forward to resurface and shoves them sideways to achieve a lateral lunge or the famous crocodile roll.
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