Dec 24 2020
In this most wonderful time of the year, Christmas is naturally on the mind of many people around the world. With only a few days left until the holiday is upon us, folks are preparing in many different ways. To those people who like to build yearly nativity scenes, your Christmas preparations might involve a surprising group of organisms—lichens. It is not uncommon in some cultures, where it is tradition to make beautiful and detailed miniature replicas of the nativity scene in their homes, to decorate the scene with a variety of lichens and mosses. The lichens especially stay dry, rigid and healthy-looking for quite some time, standing in for trees, bushes and grasses in the diorama.
Perhaps the most common lichens used in these models (and in model-making in general) are the reindeer lichens, a group of morphologically similar lichens in the genus Cladonia. While the name might suggest they grow only amongst reindeer, these diverse species are widespread across the globe. Most often found in exposed areas with minimal canopy cover, it is rare to find a single species on its own—appearing as a dense bundle of bushy white or pale green branches atop stone, soil or sand—the reindeer lichens enjoy living communally, living happily amongst other Cladonia species. In some habitats, reindeer lichens are early successors, establishing after a disturbance until plants overgrow them (Uotila et al. 2005). In other habitats such as boreal forest glades, they are the final stage of succession, holding fields of sprawling lichen mats under their control for long stretches of time (Magnusson 1982). Many animals also make a meal of these beautiful lichens, from deer and moose to—yes—even caribou (reindeer). In fact, the gray reindeer lichen, Cladonia rangiferina, even gets its scientific name from its relationship with the caribou (otherwise known as Rangifer tarandus).
Caribou specifically rely heavily on reindeer lichens during the winter months, to the point where it becomes the most prominent component of their diet. While most of the species caribou eat are as white as the snow that covers them, these animals have the capacity to sniff out the lichens from beneath even a heavy snow blanket (Lance and Eastland 2000). In fact, a considerable portion of a caribou’s day in the winter is spent digging reindeer lichens out from under the snow. These lichens aren’t quite as nutrient-rich as the plants caribou eat outside of winter however, so one might consider the reindeer lichens almost like a snack to hold the caribou over, until the main course is brought out. No doubt that, as Christmas Eve is rapidly approaching, Santa’s reindeer are enjoying some tasty lichen snacks right now, in preparation for their big flight.