Females can activate their testes and deactivate their ovaries.
Did you know that most so-called poisonous snakes aren't poisonous at all, but actually venomous?
Can animals grow infinitely big in the right conditions? Learn more on this Moment of Science.
Almost all mammals, in fact, have REM sleep; birds do too, although only in the early parts of their lives. It seems that sleep and REM are required by a particularly complex kind of brain.