Dg. Hewitt et Rl. Kirkpatrick, FORAGE INTAKE RATES OF RUFFED GROUSE AND POTENTIAL EFFECTS ON GROUSE DENSITY, Canadian journal of zoology, 74(11), 1996, pp. 2016-2024
One hypothesis to explain low densities of ruffed grouse (Bonasa umbel
lus) in the southeastern United States is that available winter forage
s 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 hy
pothesis, we conducted trials with captive ruffed grouse to determine
their maximum instantaneous rates of intake of various forages and use
d the results to estimate minimum foraging times for southeastern ruff
ed grouse consuming an average winter diet. Grouse in the Southeast mu
st forage for >100 min to meet their energy demands. Ruffed grouse in
the central portion of the range rely heavily on aspen (Populus sp.) b
uds 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 mortal
ity rates.