A pale gray-green branching lichen (a symbiosis of fungus and alga) that carpets boreal forest floors and arctic tundra. The primary winter food of caribou and reindeer.

Also called: Reindeer Moss (technically incorrect — not a moss), Caribou Moss

Native status: Native; circumboreal Arctic and subarctic

§ Quick facts

SizeIndividual thallus 5–10 cm tall; clonal carpets cover hundreds of square meters
WeightN/A
LifespanIndividual thallus may live 100+ years; clonal mats persist for centuries
OrderLecanorales
FamilyCladoniaceae

§ Encyclopedia

Cladonia rangiferina, also known as reindeer cup lichen, reindeer lichen or grey reindeer lichen, is a light-coloured fruticose, cup lichen species in the family Cladoniaceae. It grows in both hot and cold climates in well-drained, open environments. Found primarily in areas of alpine tundra, it is extremely cold-hardy.

Source: Wikipedia — Cladonia rangiferina Licensed under CC BY-SA 4.0

§ Identification

Field marks. Pale gray to white intricately branched lichen forming dense ground-covering mats; rounded "knobby" tips on branches.

Similar species. Other Cladonia species (different growth forms). Iceland Moss (lichen with different texture; flat thallus).

Voice. N/A

§ Diet & behavior

Diet. Photosynthesis (via algal partner) supplemented by atmospheric nutrients; absorbs water primarily from rain and fog.

Behavior. Not a single organism but a lichen symbiosis between a fungus (Cladonia rangiferina) and a green alga (Asterochloris). Primary winter food of caribou and reindeer — entire herds dig through snow to reach lichen carpets, and overgrazing or fire damage can render summer ranges uninhabitable for 50–100 years. Among the most pollution-sensitive organisms known — disappears from areas with significant SO₂ pollution, making it a "biomonitor" species for air quality.

§ Range

Boreal North America, mountain tundra

§ Habitat

Open boreal forests, alpine tundra, sandy barrens

§ Threats

Air pollution (lichens are extremely sensitive), boreal logging, caribou population crashes, climate-driven shifts.

§ Conservation status

According to the IUCN Red List, the reindeer lichen is currently classified as Least Concern.

§ What helps

Support clean-air policies. Avoid trampling lichen carpets in alpine/arctic. Support boreal forest protection.

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§ Further reading

§ Sources cited

  • USDA Forest Service Lichen Air Quality program
  • Canadian Forest Service
  • Smithsonian Arctic Studies Center