A toxic, slimy, sexy concoction...
In some drier areas, a thin mucous layer isn't enough protection.
Phyllomedusa sauvagei is a large South American tree frog which spends much of its time in tree
tops where the wind and heat can cause rapid water loss from evaporation. When P. sauvagei
settles into a resting pose, special glands in its skin secrete a waxy substance which the frog then
rubs all over its body. When dry, the waxy coat provides enough waterproofing to lower the
frog's rate of water loss close to that of a desert iguana!
In addition to lubricating and protecting the skin, glands can function in communication. For example, "hedonic" glands produce pheromones used in courtship. The use of chemical signals is particularly important in the salamanders since they can't vocally announce their sexual readiness as the frogs do.