Meeting Abstract
137.5 Monday, Jan. 7 Growing Fast and Dying Young: Influence of Forage Quality on Growth and Survival of Arctic Avian Herbivores RICHMAN, S.E.*; MCWILLIAMS, S.R.; LEAFLOOR, J.O.; KARASOV, W.H.; University of Rhode Island; University of Rhode Island; Environment Canada, Winnipeg, MB; University of Wisconsin-Madison cruciger7@gmail.com
Keystone herbivores such as geese in Arctic ecosystems are highly sensitive to reduced quantity and quality of available forage like that caused by overgrazing. To determine the effects of diet quality on growth and survival of sympatric goose populations, we raised 100 Canada and 100 Snow goose goslings on grass-based diets that included a factorial combination of three levels of protein (10, 14 and 20%) and two levels of neutral detergent fiber (30 and 45%), but similar energy content (~18 kJ/g). Survival of Snow but not Canada goslings was significantly affected by both dietary protein and fiber content. Goslings fed the low protein diets had ~40-65% lighter body mass and reduced structural growth compared to goslings raised on the higher protein diets. The effects of dietary fiber were more extreme for Snow compared to Canada gosling in part because Canadas increased food intake (corrected for body size) by ~100% while Snows increased food intake by only 15% when fed the high-fiber diets. Apparent Metabolizable Energy was similar between species, but lower for diets with high fiber content. Canada goslings had larger gizzard mass and small intestine length than Snow goslings in response to increased fiber content. These results indicate that Snow gosling had higher protein requirements than Canadas, and that there were interspecific differences in compensatory growth that were explained by their digestive physiology. Although phenotypic flexibility in gosling growth and digestive system allows geese to respond successfully to habitat change, there appears to be a lower limit to the quality of forage eaten (<10% protein and high fiber) that is to a degree species-specific.
