Koalas require a lot of sleep because their food gives them very little energy and eucalyptus requires a lot of energy to digest. Basically most of their energy is spent on digesting the eucalyptus they eat.

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Elk shed and regrow their antlers every year

Starfish are carnivores and eat critters like clams, oysters, and mussels. And clams can flee predators. 

Orcas will play with stinging jellyfish like a dog plays with a ball

Blue-green algae can create poisonous cyanotoxins that make people, pets, and other animals sick

Gaboon vipers do not release their prey after a bite; they hang on

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