Quite a lot. Toads have two prominent glands behind and above their eyes and sometimes have an extra pair on their thighs. These glands secrete a smelly and sticky white fluid that the toads use for defence. It is an unpleasant irritant that potential predators dislike and this puts them off eating the toad. If a predator does grab hold of the toad, the glands go into overdrive and the fluid starts to burn the delicate tissues in the predator’s mouth.

The active ingredients of the toxin produced by the glands of the toads have been studied quite intensively over the years. The toxic substance is a complex mixture of chemicals that have many different effects. One is similar to digitalis, the substance derived from fox gloves that is used to treat heart failure. This could explain why the ancient Chinese used toad skins to treat circulatory problems.

Such natural secretions can reveal many potential new drugs that can be developed by the pharmaceutical industry. A lot of drugs with this sort of natural origin often turn out to be more effective that those the chemists try to design.