The medium used to create the art was bat guano.

It was the bat guano they couldn't handle.

Most of the life in this cave is supported by large amounts of bat guano.

Have you got a bit of bat guano on you?

And bat guano sells as fertilizer at the central market for 18 cents a pound.

Population estimates were derived from the accumulation of bat guano.

The living species are believed to be associated with bat guano.

Mummified rat and snake on top of rocks in bat guano.

He had it mined for bat guano, a valuable natural fertilizer.

Let's see, I need a ball of bat guano and a pinch of sulfur.