Which animals eat lichens

The lichen carpet in some regions of tundra provides the major source of food and nutrients for the big herbivores, which in turn are a primary food source for wolves. Odd to think that such an awesome predator ultimately depends on a combination of a fungus and algae. More than 17, species of lichens have been described, most belonging to the fungus group that includes the edible morel mushrooms. What might seem to be a fragile life form may actually be one of the toughest organisms around.

Lichens not only persist on tundra and mountain cliffs but also inhabit hot deserts and Antarctic sea water. But natural conditions do not have to be harsh for lichens to thrive. They can be found in old growth forests, wetlands, and prairies. Ironically, the durable lichens are believed to be highly sensitive to some components of modern air pollution.

They have been reported to be intolerant of toxic materials such as sulfur dioxide, heavy metals, and fluorine. Lichens have even been proposed for use as indicators of air pollution in areas with high pollution from industrial sources. One report noted a gradual decrease in lichen abundance from the outskirts of an industrial area to its center. Lichens serve as a food source for many animals besides caribou, such as moths, slugs, and mites. The bright colors on the wings of tiger moths are thought to warn bird predators that, because the moth caterpillars eat lichens, the adult moths are distasteful.

Hummingbirds, vireos, and other birds use lichens for nest material. Lichens are even used by humans, such as for dyes including those used in Harris tweeds , antibiotic salves, and perfumes.

Indeed, they do not even have roots or require constant hydration, which is why lichens are able to grow in places that other plants cannot, such as deserts, mountaintops and frozen landscapes. Many species of lichen have become extinct due to increasing levels of sulphur dioxide since industrialisation, with others affected by ammonia from animal husbandry, atmospheric nitrogen oxides from exhaust fumes, and other pollutants such as ozone and fluorine.

While some species have seen a dramatic decrease in numbers, other species of lichen now have a wider range than they did a century ago — these species tend to have a higher tolerance to polluted air and survive in urban areas, growing on walls and pavements.

Lichens can be extremely long-lived, with some considered to be among the oldest living things on earth. Lichens grow slowly, with some only adding around 0.

Some Antarctic lichens have estimated ages of up to 5, years old. Despite growing so slowly, lichens can be amongst the first living things to grow on fresh rock exposed after an event such as a landslide.

The long lifespan and slow and regular growth rate of some lichens can be used to date events, which is called lichenometry. This all means that we can use lichens to determine many things, such as the length of time a habitat has been left undisturbed, or the effects of pollution and climate change. For comparison, the World Health Organisation recommends that levels of microcystins in drinking water should be no more than 0.

The chemicals themselves were incredibly varied. Kaasalainen found 52 different varieties of microcystins, many of which had hardly ever been seen before. She also found 30 distinct varieties of the mycE gene. Indeed, the lichens may have provided cyanobacteria with an evolutionary platform from which to diversify into many new forms. After all, we know that Nostoc strains in lichens are far more diverse than those that grow on their own.

Wolf lichen is one of them , and has been used to stuff reindeer carcasses in order to poison scavenging wolves and foxes. These poisons may protect the lichens from grazing mouths. Certainly, many animals eat lichens, including snails, voles, squirrels and snub-nosed monkeys. In winter, they are an important source of food for reindeer, which avoid the ones containing poisonous cyanobacteria.

Humans sometimes eat lichens too, and some species are used in Asian traditional medicines. Kassalainen suggests that the health risks of lichens, if any, are currently unclear, and will stay that way without more research.

Cyanobacteria produce a high variety of hepatotoxic peptides in lichen symbiosis. Image by Ryane Snow.