Sloths take two weeks to digest their food.
243
Dolphins sometimes have fun by blowing bubbles and creating rings of air underwater, which they then swim through.
17
Cats and dogs can hear ultrasound.
350
Sergeant Stubby was the only war dog to be promoted to sergeant through combat in WWI. He saved his regiment from surprise mustard gas attacks, found and comforted the wounded, and even once caught a German spy by the seat of his pants, holding him there until American Soldiers found him.
16
Dolphins can rapidly heal from extreme injuries, such as shark bites, and regenerate their original body shape.
19