Unsinkable Sam (nickname of a German ship's cat) who served on 3 warships, one German, two British, all sank in action. The cat survived each sinking, floating away on wooden planks to rescue.
19
There was a bear called Wojtek who was adopted by Polish soldiers during WW2. It carried ammunition, wrestled with soldiers, and drank beer.
40
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Cats and dogs can hear ultrasound.
350
The reindeer is the only mammal that can see UV light.
17