Forage intake rates of ruffed grouse and potential effects on grouse density

One hypothesis to explain low densities of ruffed grouse (Bonasa umbellus) in the southeastern United States is that available winter forages in the Southeast require more time to harvest than forages eaten in the central portions of the species' range, where grouse densities are greater. Longer foraging times could increase mortality rates through greater predation risk and higher energy expenditure. To test this hypothesis, we conducted trials with captive ruffed grouse to determine their maximum instantaneous rates of intake of various forages and used the results to estimate minimum foraging times for southeastern ruffed grouse consuming an average winter diet. Grouse in the Southeast must forage for > 100 min to meet their energy demands. Ruffed grouse in the central portion of the range rely heavily on aspen (Populus sp.) buds during the winter and can consume the same amount of metabolizable energy in 30–50 min. Thus, we present evidence that ruffed grouse in the southeastern United States must forage for longer periods to meet daily energy demands and therefore may experience higher winter mortality rates.