A note from the author:

I really like bats, and last year I got to spend quite a bit of time at a bat conservation center in Costa Rica, so I wanted to take a second an dispel the myth that all bats have rabies (despite perpetuating that myth in the first panel). The CDC did a study and found that only around 6% of bats have rabies, and those are bats that are sick or injured. Bats in the wild have a much lower percentage, and there are about 2 cases of rabies in the US each year. The CDC's website has a good writeup about it.
White Nose Syndrome, an infectious disease which is currently wiping out bat populations in the Northeast and is working its way south, is a much bigger concern than rabies.

Also, props to Zach Weiner, author of the wonderful comic known as Sunday Afternoon PorkFast Cheerios, for suggesting the Joker panel.