Causes and consequences of geophagy in snowshoe hares (Lepus americanus), an important generalist herbivore of the boreal forest

Abstract

Geophagy, the consumption of mineral soil, is believed to have several benefits for herbivores. Soils high in clay are often implicated in the detoxification of plant secondary metabolites. High mineral concentrations in soils may also provide nutrients that are poorly available from plants. Local observers report that snowshoe hares (Lepus americanus) use a lick in the foothills of the Brooks Range, Alaska. Using soil from this lick and other mineral supplements, I conducted a series of feeding trials on captive snowshoe hares fed felt-leaf willow (Salix alaxensis) or a formulated ration to determine whether geophagy resulted in a physiological benefit and, if so, which soil constituents are therapeutic. When fed willow leaves, hares ate more and lost less weight when they had access to soil. Access to soil increased sodium intake and dietary ratios of sodium to potassium in hares fed willow. Soil consumption resulted in higher calcium to phosphorous ratios for both diets. Across diets, higher sodium to potassium and lower calcium to phosphorus ratios corresponded to reduced weight loss. Access to pure calcium carbonate resulted in reduced weight loss in hares fed winter dormant willow twigs, suggesting that carbonates may also be an important component of this lick.