Effects of geophagy on food intake, body mass, and nutrient dynamics of snowshoe hares (Lepusamericanus)

Abstract

Geophagy is thought to have several physiological benefits to animals, including mineral supplementation and adsorption of toxins. However, these benefits have rarely been demonstrated experimentally. Using soil from a known lick in northern Alaska, we investigated the effect of geophagy on food intake and mass loss in captive snowshoe hares (Lepus americanus Erxleben, 1777) fed a formulated ration of feltleaf willow leaves (Salix alaxensis (Andersson) Coville), a preferred forage of snowshoe hares. Lick soil contained 4.8% clay, 12.5% carbonates, and had more available Na (72.7 mg·kg−1) than willow leaves. Hares fed willow leaves consumed more soil (15.2 ± 2.0 g·kg–0.75·d−1) than those fed formulated ration (9.3 ± 1.3 g·kg–0.75·d−1). Hares had higher willow intake when offered soil (45.8 ± 2.0 g·kg–0.75·d−1) than those without soil (35.0 ± 2.1 g·kg–0.75·d−1), and willow-fed hares offered soil lost less body mass (P < 0.001) than those without soil. Soil availability resulted in higher digestible intakes of N, Ca, Mg, Na, and K, but not P. These results suggest that the availability of mineral licks may alter forage use and functional response of this generalist herbivore in interior Alaska.