Dolphins – Sleep with one hemisphere of their brain at a time to remain alert while swimming.
Giraffes – Sleep in short bursts of 5-10 minutes, staying vigilant for predators.
Bullfrogs – Don’t seem to sleep at all, staying in a constant state of rest.
Bats – Sleep upside down in large groups, with complex, synchronized sleep cycles.
Koalas – Sleep up to 22 hours a day to conserve energy from their low-nutrient diet.
599 trainees passing out for taking up new challenges on border