The Basenji dog is the only dog that is not able to bark.
4
The largest earthworm on record was found in South Africa and measured 22 feet.
151
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
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Tigers can see 6 times better at night than humans.
305
Condoms were originally made of animal intestines or linen.
347