A banana slug can be 6-8 inches and their erect penis can be just as long. Also, their penises emerge from their heads. After sex, banana slugs eat each others penises.
17
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
It has been calculated that a single breath from a mature blue whale can inflate up to 2,000 balloons.
492
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
Christmas Island has bridges for crabs to stop them getting run over during the mass migration.
9