Too amusing not to mention:

[aamusedinatx]

For some male bats, sexual prowess comes with a price — smaller brains. A research team led by Syracuse University biologist Scott Pitnick found that in bat species where the females are promiscuous, the males boasting the largest testicles also had the smallest brains. Conversely, where the females were faithful, the males had smaller testes and larger brains.

"It turns out size does matter," said Pitnick, whose findings were published in December in "Proceedings of the Royal Society: Biological Science," an online journal.