Recently, Reddit user u/colonoscopescount asked, "What is your number-one obscure animal fact?" And I can honestly say, I didn't know any of them.
Please be advised that some submissions have been edited due to length and/or clarity.
1. "Army ants will create 'balls' during high water floods. The ball will roll, allowing every ant to get a breath." —H010CR0N

2. "The duck-billed platypus has no nipples to feed their offspring. Instead, milk oozes from the skin." —ChimpyChompies

3. "Vultures urinate on their legs and feet to cool off on hot days, a process called urohidrosis." —Iron_Chic

4. "Penguins have a gland above their eye that converts saltwater into freshwater." —Yeeteth_thy_baby

5. "The vast majority of Greenland sharks are blind thanks to a special parasite that eats their eyes and replaces them." —Fabled_Webs

6. "Sloths are literally too lazy to go looking for a mate, so a female sloth will often sit in a tree and scream until a male hears her and decides to mate with her." —amishsheepherder

7. "There is a genus of frog called Mini. There are only three frogs in the genus, and their scientific names are all puns: Mini mum, Mini ature, and Mini scule." —SwimmingOnMars

8. "There are no male mourning geckos. The entire species is female." —Moctor_Drignall

9. "Snakes don't have eyelids. If you see a snake blink, that's a legless lizard." —CirothUngol

10. "A common garden snail can have 14,000 teeth. Some snails grow 25,000 teeth in their lifetime. And the teeth grow on their tongue." —doublestitch

11. "When caterpillars enter the chrysalis phase, they don’t just sprout wings; their entire body first turns into a liquid, soupy substance, which then reforms into the butterfly." —Unlucky-Pomegranate3

12. "Some species of bats practice oral sex. Apparently certain species of male bats found out that if they satisfy the female enough, that she will not go mate with another male, thus securing their place as a father of the offspring." —Novel_Jelly8482

13. "Tarantulas have pet frogs. The frogs eat bugs and parasites that would damage the spider’s eggs, and in turn the spider protects the frog. Even after the eggs hatch, they continue to protect the frog." —Hazmatix_art
