Consumption of two birch species by captive mountain hares (Lepus timidus) in relation to resin and phenolic content

PALO, R.T.; GOWDA, J.H.; HODAR, J.

Clemont Ferrand

Workshop; XIIth Lagomorph Workshop; 1996

The species Betula pubeschens and B. pendula are common in the diet of mountain hare during winter. These species differ in their composition of secondary chemistry notably phenolics and isoprenoid resins. The concentration of phenols in twigs of B. pubescens is higher than in B. pendula in the same microhabitat, while the isoprenoid content is higher in the latter. Mountain hare is able to recognize differences in plant chemistry by smell and taste. They consume significantly less pellets containing phenols irrespective of species but consumed more pellets with phenolic extract from B. pendula than pellets based on twigs of B. pubescens. They rejected intact twigs of B. pendula, but consumed twigs of B. pubescens. The excretion of phenolics is higher in urine than in feces for both species. Resin glands of B. pendula apparently is  an effective defense line against feeding by hare, while phenols are less effective but still cause hare to minimize their intake of both species. Divergent evolution of chemical defenses and stabilizing selection due to feeding by multiple herbivores may be a reason for the persistence of two co-ocurring plant species with different defense investments.