Lemmings eat a surprisingly varied menu of tundra plants, but exactly what ends up in their stomachs depends heavily on which species you are looking at. The two most studied Arctic species, the brown lemming and the collared lemming, share the same landscape yet eat strikingly different things. Brown lemmings lean heavily on grasses, sedges, and mosses, while collared lemmings favor shrubs and herbs. This dietary split is one of the reasons both species can coexist across the same stretches of Arctic terrain without starving each other out, and it has cascading effects on the tundra ecosystem that researchers are still working to fully understand.
Brown Lemmings and Collared Lemmings Eat Very Different Plants
The clearest finding from decades of lemming diet research is that brown lemmings (Lemmus sibiricus) and collared lemmings (Dicrostonyx groenlandicus) partition the tundra buffet between them. Stomach content and fecal analyses near Barrow, Alaska, showed that brown lemmings ate primarily grasses, sedges, and mosses, while collared lemmings ate primarily willow leaves and forbs.1Journal of Mammalogy. Nutritional Ecology of Microtine Rodents: Food Habits of Lemmings near Barrow, Alaska Cafeteria-style feeding trials, where captive lemmings were offered a spread of tundra plants and allowed to choose freely, confirmed the same pattern: brown lemmings preferred graminoids and moss, and collared lemmings preferred shrubs and herbs.2Canadian Journal of Zoology. Diet selection in Arctic lemmings (Lemmus sibericus and Dicrostonyx groenlandicus): food preferences
This is not a casual preference. The split runs deep enough that it shapes where each species forages. Brown lemmings tend to stick to wet meadows and sedge-dominated lowlands where their preferred grasses and mosses grow thickly. Collared lemmings favor drier, better-drained ridges and slopes where dwarf shrubs like mountain avens (Dryas integrifolia) and Arctic willow (Salix arctica) thrive. The result is a kind of natural zoning, two herbivores occupying the same general habitat but targeting different plant communities within it.
What Drives Their Food Choices
When researchers compared lemming food preferences against the chemical and physical makeup of the plants on offer, the biggest factor was straightforward: calories and macronutrients. Both species gravitated toward plants with higher caloric content and more accessible nutrition.2Canadian Journal of Zoology. Diet selection in Arctic lemmings (Lemmus sibericus and Dicrostonyx groenlandicus): food preferences But the differences between the two species came down to secondary plant compounds and physical traits. Collared lemmings showed a greater capacity than brown lemmings for handling the downsides of their preferred plants, such as defensive chemicals and the presence of plant hairs, which can make digestion harder.2Canadian Journal of Zoology. Diet selection in Arctic lemmings (Lemmus sibericus and Dicrostonyx groenlandicus): food preferences
This makes sense when you consider what each species is eating. Willows and shrubs tend to produce more defensive chemicals than grasses and mosses. A collared lemming that could not tolerate those compounds would struggle to survive on its preferred diet. Meanwhile, brown lemmings avoid that challenge entirely by sticking to plants that are lower in toxins but also lower in certain nutrients, compensating by eating a lot of it.
Interestingly, the idea that tundra plants fight back by ramping up chemical defenses after being grazed has not held up well under testing. When researchers simulated herbivory on forage plants in Norwegian alpine rangelands, most plants either showed no response to the damage or actually had reduced levels of defensive compounds afterward.3PubMed. Effects of simulated herbivory on defensive compounds in forage plants of norwegian alpine rangelands So at least in some tundra environments, plants do not seem to be escalating a chemical arms race against their grazers in the way that was once hypothesized.
How Winter Changes the Menu
Summer in the tundra offers an abundance of fresh growth, but winter buries everything under snow for months. Lemmings do not hibernate. They stay active year-round, tunneling through the basal snow layer to reach vegetation on the ground. This means their winter diet depends on what is available under the snowpack, and it shifts accordingly.
For brown lemmings, the summer-to-winter shift is substantial. In summer, graminoids like grasses and sedges dominate their diet with some mosses mixed in. In winter, this reverses: mosses become the primary food and graminoids drop to a supplementary role.4Canadian Journal of Zoology. Diet selection in Arctic lemmings (Lemmus sibiricus and Dicrostonyx groenlandicus): forage availability and natural diets Mosses stay green and accessible beneath the snow, and they are often one of the few things a brown lemming can easily reach when the ground is frozen.
Collared lemmings show more dietary consistency across seasons. Their summer and winter diets were both dominated by the evergreen shrub Dryas integrifolia, supplemented by Arctic willow.4Canadian Journal of Zoology. Diet selection in Arctic lemmings (Lemmus sibiricus and Dicrostonyx groenlandicus): forage availability and natural diets Because Dryas is an evergreen with tough, persistent leaves, it remains available even in midwinter when deciduous plants have lost their foliage. This gives collared lemmings a more stable food base year-round, at least in terms of what they are eating, even if the effort required to access it changes with snow conditions.
Foraging Under the Snowpack
The way lemmings find food in winter is inseparable from the snow itself. They do not just survive under snow; they depend on it. The snowpack provides insulation from air temperatures that can plunge far below freezing, and the basal layer of snow nearest the ground often develops into a soft, crystalline structure called depth hoar, which lemmings can dig through relatively easily to reach the plants underneath.
A long-term study on Bylot Island in the Canadian High Arctic tracked lemming winter nests for 13 years and snow properties for 6 years across four different habitat types. Lemmings used riparian habitats most intensively because snow accumulated faster there, the snowpack was the deepest, and the temperature at the base of the snow layer was the highest.5PubMed. Lemming winter habitat: the quest for warm and soft snow Warmth and depth are both critical: deeper snow means better insulation and more room to build nests and tunnel networks. But the study also found a trade-off. In the deepest snowpacks, the basal depth hoar layer was denser and less developed, making it harder to dig through. Those conditions were negatively related to lemming reproduction in winter.5PubMed. Lemming winter habitat: the quest for warm and soft snow
This trade-off matters because lemmings breed under the snow. A female that cannot dig efficiently to reach food burns more energy for less reward, which reduces her ability to nurse pups through the winter. So the best winter habitat is not simply wherever snow is deepest. It is wherever the combination of depth, warmth, and snow texture allows lemmings to move freely and reach food without exhausting themselves.
A Gut Built for Low-Quality Food
Eating mosses and grasses all winter is not easy. These are bulky, fibrous, nutrient-poor foods, and breaking them down takes specialized equipment. Lemmings, especially brown lemmings, have digestive tracts adapted for the task. The Norway lemming (Lemmus lemmus), a close relative of the brown lemming, has an unusually large post-caecal spiral in its gut and a longer colon than many comparable rodents. Researchers have linked this to the demands of its preferred diet, which is low in easily digestible nutrients.6Comparative Biochemistry and Physiology. Adaptations of the caecum-colon structure of rodents
A larger fermentation chamber and longer intestinal transit time give gut microbes more opportunity to break down cellulose and extract whatever nutrition the food has to offer. Think of it as a longer conveyor belt in a factory: the raw materials are not great, so the production line has to run slower and longer to get anything useful out of them. This is a common adaptation among herbivorous rodents, but the degree of specialization in lemmings reflects just how much of their diet consists of plants that most other small mammals would pass over.
How Lemming Grazing Reshapes the Tundra
Lemmings are small, but they eat in enormous numbers during population peaks. The cumulative effect on tundra vegetation is real and measurable. Long-term exclosure experiments in Fennoscandian highland tundra, where fences kept lemmings and other mammalian herbivores out for years, showed strong increases in overall plant biomass when grazers were absent. Both palatable plants like graminoids and large mosses, and less palatable plants like evergreen shrubs and lichens, all increased when lemmings were excluded.7Ecosystems. Long-Term Experiments Reveal Strong Interactions Between Lemmings and Plants in the Fennoscandian Highland Tundra One of the more interesting findings was that palatability turned out to be a poor predictor of which plants responded most to the removal of grazers. The plants that grew the most were not necessarily the ones lemmings preferred eating. Instead, the biggest gains went to species that were capable of accumulating the most biomass when freed from grazing pressure.
Broader comparisons across Scandinavia and Alaska confirmed the pattern. Vegetation density was consistently lower where herbivores, including lemmings, were present compared to areas where they had been excluded for two to three decades.8PubMed Central. Large and small herbivores have strong effects on tundra vegetation in Scandinavia and Alaska Lemmings are not the only grazers in the tundra, of course. Reindeer, muskoxen, and geese all contribute. But lemmings operate at a different scale, clipping vegetation close to the ground and accessing plants under snow that larger herbivores cannot reach. Their influence on mosses and the ground layer of vegetation is particularly outsized relative to their body mass.
When Geese Eat the Lemmings’ Food
Lemmings do not always have the tundra to themselves. In some parts of the Arctic, large goose colonies create a different kind of competition. At a major nesting colony near Karrak Lake in Nunavut, heavy grazing by Ross’s geese and lesser snow geese stripped graminoid plants from lowland areas almost completely. The result was a dramatic reduction in small mammal numbers: lemming and vole abundance inside the colony was roughly an order of magnitude lower than in comparable lowland areas outside it.9Canadian Journal of Zoology. Habitat alteration by geese at a large arctic goose colony: consequences for lemmings and voles
This is worth paying attention to because Arctic goose populations have been growing in recent decades, partly due to agricultural food subsidies on their wintering grounds farther south. As colonies expand, they degrade more tundra habitat, and the species that depend on that habitat, lemmings included, get squeezed. For brown lemmings in particular, whose diet revolves around grasses and sedges, losing those plants to goose grazing is a direct hit to their food supply.
Lemmings as Tundra Fertilizers
What goes in must come out, and lemming droppings play a role in tundra nutrient cycling that goes well beyond what you might expect from an animal that weighs less than a smartphone. Lemmings concentrate nutrients in specific spots: latrines, winter nests, hay piles (small food caches), and burrow entrances. Each of these structures affects the soil underneath in different ways.
Across multiple study regions, hay piles, though relatively uncommon, increased several soil nitrogen and phosphorus pools along with enzyme activities involved in carbon and nitrogen cycling. Latrines had a broader spatial footprint and also influenced carbon, nitrogen, and phosphorus pools, though the effects varied by region.10Functional Ecology. Small but mighty: Impacts of rodent‐herbivore structures on carbon and nutrient cycling in arctic tundra Finer-scale work found that soil under winter nests tended to have higher ammonium levels, while burrows showed lower nutrient levels compared to undisturbed soil, suggesting that digging itself may disrupt nutrient accumulation.11PubMed Central. The Effect of Structure Building Small Mammals in a Shifting Arctic Landscape
The broader implication is that lemmings are not just consumers of tundra plants. They are also redistributing nutrients across the landscape. During population peaks, the sheer volume of fecal matter they produce may help the ecosystem recover from the heavy grazing those same peaks cause. Because fecal decomposition is slow in cold environments, the nutrients deposited during a peak year can persist in the soil across multiple years, creating legacy effects on plant growth long after lemming numbers have crashed.12PubMed. When top-down is also bottom-up: Examining consumer-driven nutrient recycling in an arctic herbivore population In other words, lemmings eat the tundra down and then, through their waste, help it grow back.
Lemmings, Willows, and a Warming Arctic
Climate change is reshaping the tundra in ways that intersect directly with what lemmings eat. One of the most visible changes is the northward expansion of shrubs, especially willows. Warmer temperatures favor shrub growth, and across much of the circumpolar Arctic, researchers have documented increasing cover of erect willows and other woody plants in areas that were once open tundra.
Lemmings may be acting as a brake on this process. Both brown and collared lemmings consume willows, and in peak population years, small rodents can cause severe damage to willow saplings. In parts of northern Norway, up to 90% of willow saplings have been killed during rodent population peaks.13PLOS ONE. Highly Overlapping Winter Diet in Two Sympatric Lemming Species Revealed by DNA Metabarcoding On Bylot Island, where snowbed habitats are generally favorable for erect shrub growth, the consumption of Salix by both lemming species present could limit the encroachment of erect shrubs despite warming conditions.13PLOS ONE. Highly Overlapping Winter Diet in Two Sympatric Lemming Species Revealed by DNA Metabarcoding
Whether lemmings can actually keep up with shrub expansion in the long run is an open question. Lemming population cycles are themselves affected by climate change, particularly through changes in snow conditions. If warmer winters produce less favorable snowpacks, with denser basal layers, harder to tunnel through, and fewer insulating air pockets, lemming populations could decline or cycle less dramatically. That would remove one of the key checks on shrub encroachment, potentially accelerating the transformation of open tundra into shrubland. The tundra’s future plant community may depend, in part, on whether conditions stay favorable enough for a rodent that most people only know from a myth about mass suicide.
How Winter Nests Reveal What Lemmings Really Eat
Figuring out what a small, elusive animal eats in the depths of an Arctic winter is not straightforward. You cannot exactly follow a lemming through its tunnels with a clipboard. Traditional approaches relied on stomach contents and fecal pellet analysis, which involve collecting samples and identifying plant fragments under a microscope. These methods work, but they have a bias toward plants with tough, recognizable cell structures. Soft-tissued plants and fungi tend to get digested beyond recognition, so they are underrepresented in the results.
More recently, researchers have turned to DNA metabarcoding, which extracts and sequences tiny fragments of plant DNA from fecal samples. This method can detect plants that would be invisible under a microscope, and it has expanded the known winter diet of lemmings to include species that traditional methods missed. The dietary overlap between brown and collared lemmings in winter turned out to be higher than previously thought, which raises questions about how the two species avoid competing too directly when food is scarcest.13PLOS ONE. Highly Overlapping Winter Diet in Two Sympatric Lemming Species Revealed by DNA Metabarcoding
Winter nests themselves are another data source. When the snow melts in spring, lemming nests are left behind on the ground surface, along with latrines and food caches. Researchers can survey these structures across large areas to infer where lemmings were active, what they were eating, and how successfully they bred. The density of nests in a given habitat type reflects both the quality of the snow for tunneling and the availability of food plants underneath. Riparian areas, with their deep, warm snowpacks and relatively rich plant communities, consistently show the most intensive use. But even there, the balance between snow depth and snow texture creates trade-offs that keep lemmings from simply piling into the best-looking habitat and staying put.