Rock Tripe is a type of lichen that is briefly mentioned in the DreamWorks Dragons Franchise.
To keep organization on the How to Train Your Dragon Wiki, Rock Tripe will be classed under 'Plants', though, in fact, Rock Tripe are in the Kingdom Fungi.
Rock tripe is the common name for lichens in the genus Umbilicaria. These lichens can be found growing on rocks throughout the northern parts of North America, but can be found in other parts of the world, such as Europe and Asia.
In the Franchise, the only known function for rock tripe is to be the food of specific dragons, particularly Buffalords.
In real life, if prepared correctly, rock tripe can be edible to humans, with it often being used as a famine food in survival situations, like those faced by early American explorers. One species, U. esculenta is often used as food in China, Japan, and Korea and is also used as a restorative medicine in traditional Chinese medicine.
The Buffalord Frostgnaw is said to eat rock tripe.
|“||In the frozen north of the Barbaric Archipelago, the Frostgnaw subsists on a steady diet of sphagnum moss and rock tripe.||”|
|— Dragons: Titan Uprising|