The snowshoe hare (Lepus americanus) is a mammal of the North American boreal forests, recognizable by its seasonally changing fur and oversized hind feet, which act like natural snowshoes. As a member of the order Lagomorpha, which includes rabbits and pikas, the hare is a strict herbivore. Its diet consists entirely of plant matter, and its adaptations allow it to survive efficiently on fibrous, seasonally-variable vegetation in cold, resource-scarce environments.
Seasonal Variation in Diet
The diet of the snowshoe hare undergoes a shift with the change in seasons, driven by the availability and nutritional content of local flora. During the summer months, when food is abundant, the hare consumes soft and nutritious herbaceous plants. This includes grasses, clovers, ferns, and the new, supple growth of woody vegetation.
Winter forces the hare to rely on much tougher, less digestible sources, primarily consisting of woody browse. They consume the bark, buds, and small twigs of deciduous trees such as willow, birch, and aspen, in addition to the needles of evergreens like spruce. This winter fare is lower in protein and readily available energy, necessitating specialized methods to extract sufficient nourishment.
Specialized Digestive System
Successfully processing the snowshoe hare’s high-fiber diet requires a specialized digestive strategy. Hares are hindgut fermenters, relying on the cecum, a large, pouch-like organ located between the small and large intestines, to break down cellulose. The cecum is a fermentation chamber where symbiotic bacteria digest tough plant fibers that the hare’s own enzymes cannot process.
This bacterial action converts the indigestible fiber into volatile fatty acids, which the hare can absorb, and also synthesizes B vitamins and essential microbial proteins. Because the cecum is positioned after the main site of nutrient absorption in the small intestine, the hare employs a process called cecotrophy to reclaim these products. During this process, the hare produces soft, moist pellets, known as cecotropes, which are rich in the newly synthesized nutrients.
The hare consumes these cecotropes directly from the anus, effectively passing the food through the digestive tract a second time. This re-ingestion allows the stomach acid to kill the bacteria and the small intestine to absorb the microbial protein, B vitamins, and vitamin K produced in the cecum. This double-digestion mechanism enables the animal to maximize nutrient extraction from a low-quality, high-fiber food source.
Role in the Ecosystem
The snowshoe hare is a primary consumer in the boreal forest food web, serving as a major conduit for energy transfer. Their browsing habits have a direct effect on local plant communities, especially in winter when they can create distinct “hare lines” on shrubs by clipping stems up to a certain height. During periods of high population density, hares can severely damage or kill saplings by girdling, which involves stripping a ring of bark from the tree’s circumference.
The species is famous for its population fluctuations, cycling between periods of abundance and scarcity over an approximate 8- to 11-year period. This cycle directly influences the population dynamics of its primary predators, most notably the Canada lynx. As the hare population rises, providing a plentiful food source, the lynx population increases with a slight time lag.
When hare numbers crash, often due to intense predation and food stress, the lynx population follows suit, demonstrating the hare’s significance in regulating predator numbers. The hare is a central species whose abundance dictates the health and structure of the northern ecosystem. Its consumption of plants and its role as a prey item link the producer and carnivore trophic levels.