Rain is an essential ingredient of any farming enterprise. When a rain event is desperately anticipated, especially in a dry year, farmers will sometimes look to animal behavior as a rainfall predictor. Some believe if a kookaburra calls in the middle of the day it’s a sure sign of rain, while others consider a bearded dragon sitting on a fence post to be a reliable indication that it will rain in the next three days.
One dependable indicator of moisture in the environment is Mallee Popcorn - Xanthoparmelia semiviridis. Mallee popcorn is a vagrant lichen meaning it is not attached to the substrate but rather tumbles around the environment. This is an adaptation that has allowed the species to thrive in sandy soils where the surface is highly mobile.
When there is no moisture Mallee Popcorn dry out and roll up into a tight ball. When there is rain or heavy dew they re-hydrate causing them to unroll and flatten (as seen in the photograph). Mallee popcorn can hold up to three and a half times its dry weight in water and it is in this state that the lichen will photosynthesize.
When the lichen is dry and rolled up it can be blown around in strong winds. This allows it to not only disperse through the environment but also helps with reproduction. Wind may force the lichen against objects such as rocks, causing pieces to break off and new individuals to form.
A Bearded Dragon sitting on a fence post is said to be a sign that good rain is coming. Some even say the direction the lizard is facing will predict the direction the rain will come from.