Fun Fact Friday (#70)

Fun Fact Friday is a meme hosted by Lettora at I’m Booked! If you’d like to join and do your own Fun Fact Friday, just ask! At I’m Booked! Every week we’ll give you five new, fun facts. 

This week’s five facts: 

1. At the center of every raindrop is an impurity such as dust, clay or soot. It is almost impossible for raindrops to form from pure water.

2. The opah, or "moonfish", is the only known fully warm-blooded fish.

3. The lifespan of a squirrel is about nine years.

4.  A group of twelve or more cows is called a flink.

5.  Fingernails grow nearly 4 times faster than toenails.