Ruffed Grouse Consumption and Detoxification of Evergreen Leaves

Abstract

Ruffed grouse (Bonasa umbellus) in the southeastern United States commonly eat evergreen leaves during winter. Despite their abundance, these leaves rarely make up >50% of the diet. We fed diets containing 20 and 40% mountain laurel (ML) (Kalmia latifolia) and Christmas hollyfern (CHF) (Polystichum acrostichoides) to captive ruffed grouse to determine the bird's ability to exist on these forages and to investigate detoxification of secondary plant compounds. Grouse consuming diets with 20% of test forages performed similar to grouse eating a control diet. Diets with 40% of the test forages caused reduced intake and birds consuming the CHF diet were unable to maintain body mass. Conjugate-based detoxification systems were stimulated by both test forages, although detoxification strategies varied between forages and levels of forage in the diet. Although grouse appear unable to exist solely on evergreen leaves, these forages probably contribute to ruffed grouse winter survival by remaining available during snow accumulation and by decreasing foraging times due to high intake rates.