The relationship between the arctic fox and polar bears and that between pitcher plant midges and mosquitoes are examples of commensalism in the tundra biome. Commensal interactions provide an advantage to an individual of one species without either benefit or damage to its benefactor.
The arctic fox scavenges the remnants of polar bear kills, following the bears without interacting. The fox gains food in the relationship, but the polar bear is not impacted.
Midge and mosquito larvae live in pitcher plants feeding on the invertebrate carcasses captured by the plant leaves. Although both depend on the same food source, the relationship between the species is not competitive. Similar to the fox, the mosquito larva eats the food after initial processing by the midges. This particular form of commensalism, named processing chain commensalism, occurs when two species use the same food source but at different points of its breakdown.
Another form of commensalism is in the distribution of lichen over vast areas of the Arctic tundra by birds and mammals. The lichen spores adhere to the bird feathers and are transported by the birds in their migrations. The birds are unaffected by the transaction.
Some researchers believe that commensalism is non-existent, as any interaction provides a benefit or damage to both participants, even if too small to be readily apparent, according to Clark University.