Mosses, ancient and diverse non-vascular plants, thrive globally in diverse habitats, from tropical rainforests to polar tundras. These small, flowerless plants form dense mats, absorbing water and nutrients directly through their leaves. While not a primary food source for many large animals, a surprising array of invertebrates and vertebrates incorporate moss into their diets. They consume moss for nutritional benefits, moisture content, and as a survival food when other vegetation is scarce.
Invertebrate Moss Consumers
Many invertebrate species feed on mosses, often playing a role in their ecosystems. Slugs and snails are common examples, utilizing their rasping mouthparts, called radulae, to graze on moss. Moss provides moisture and nutrients for snails. They typically consume live moss, as dry moss is more difficult to digest.
Certain insect larvae also consume mosses. Crane fly larvae, for instance, are known to feed on decaying plant matter, which can include moss. Some beetles, known as “moss beetles,” graze on moss in damp environments.
Another group, the moss bugs (Peloridiidae), are flightless insects that exclusively feed on mosses and liverworts. Springtails, small invertebrates often found in moist soil and leaf litter, also include moss as part of their diet. Mites, microscopic arachnids, can also be found feeding on mosses. These invertebrates often chew or rasp at the moss tissue, contributing to the breakdown of plant material within their habitats.
Vertebrate Moss Consumers
Vertebrate animals also incorporate moss into their diets, although it is often a supplementary food source rather than a primary one. In colder climates, where other vegetation can be scarce, mosses become a more important food. Reindeer (caribou) consume moss, especially in winter when other food sources are limited. While they preferentially consume lichens like “reindeer moss” (which is technically a lichen, not a true moss), they will eat true moss species in low-lichen regions or when lichens are overgrazed. Moss can constitute a significant portion, sometimes up to 55%, of a Svalbard reindeer’s winter diet.
Muskoxen, large bovids inhabiting the Arctic, also include moss in their diet, particularly during winter months. Moss consumption by muskoxen increases in low-lichen regions and higher latitudes. Lemmings, small rodents found in arctic and subarctic regions, commonly eat moss, which can make up nearly half of their winter diet in some areas.
The wood lemming, for example, primarily consumes moss, preferring species like Dicranum for their nitrogen content. American pikas, small mountain-dwelling mammals, can also rely heavily on moss, with some populations consuming up to 60% moss in their diet, especially in cooler microclimates. Some bird species, such as barnacle geese, feed heavily on mosses during winter, and certain geese species in the sub-Antarctic have been observed to deliberately forage on mosses.
Ecological Role of Moss Consumption
The consumption of moss by various animals contributes to the intricate web of ecological processes within their habitats. While mosses are not typically at the base of extensive food chains, their consumption facilitates nutrient cycling and energy transfer within ecosystems. Animals that feed on moss help break down plant material, returning nutrients to the soil through their waste products. This process supports the overall health and productivity of the environment.
The feeding habits of moss consumers can also influence moss populations directly. In some cases, heavy grazing by herbivores can lead to localized declines in moss cover, potentially altering the microhabitat for other organisms that rely on moss for shelter or moisture. Conversely, the ability of moss to grow in harsh environments makes it an important survival food source for animals when other vegetation is scarce, particularly in cold or nutrient-poor regions.
The high fiber content of moss, while challenging to digest for some, provides essential roughage and can be a source of arachidonic acid, which is beneficial for animals in cold temperatures. Some animals, like pikas, have adapted unique digestive strategies, such as coprophagia, to extract more nutrients from their high-fiber moss diet. Thus, moss consumption plays a role in the resilience of animal populations and the dynamic balance of the ecosystems they inhabit.