Bullfrog Bullfrogs can go months without sleep and enter a state of dormancy, which is a state of inactivity and lowered metabolism, instead of following a sleep-wake cycle.
DolphinDolphins develop a special mechanism called unihemispheric sleep, which allows one-half of their brain to rest while the other stays awake to watch for predators.
Alpine SwiftAlpine Swifts fly for months, taking brief naps while airborne. During this time, they enter a state of inactivity to conserve energy.
BluefishThey do not sleep since their constant movement helps with breathing and hunting. These animals also use their lateral line organ to detect water vibrations.
Walrus Walruses swim for up to 84 hours without sleep but make up for it by sleeping up to 19 hours on land.
ElephantElephants sleep around two hours daily and stay active to maintain social bonds as well as forage for food.
GiraffeGiraffes sleep briefly, from minutes to two hours a day. They stay alert due to their height and predator risk.
DeerDeers sleep minimally when migrating or facing threats and stay semi-alert, ready to flee at any point.
SharkSome sharks must constantly swim to breathe, experiencing periods of low activity but never fully sleeping.
HorseHorses can sleep standing up, requiring only two hours of REM sleep daily to stay alert for predators.