Effect of browse on post-ingestive energy loss in an Arctic ruminant: implications for muskoxen ( Ovibos moschatus ) in relation to vegetation change

• Published in: Canadian Journal of Zoology
• Main Authors: Lawler, James P., White, Robert G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2006
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Arctic; Betula nana; Global warming; ovibos moschatus; Tundra
• Online Access: http://dx.doi.org/10.1139/z06-145; http://www.nrcresearchpress.com/doi/full-xml/10.1139/z06-145; http://www.nrcresearchpress.com/doi/pdf/10.1139/z06-145

Shrubs are predicted to dominate tundra with warmer temperatures at northern latitudes. We tested the null hypothesis that addition of browse to a graminoid diet would not alter post-ingestive energy loss in muskoxen ( Ovibos moschatus (Zimmermann, 1780)). Energy losses over 8 h following feeding were used to test our hypothesis. Willows ( Salix alaxensis (Anderss.) Coville, Salix planifolia ssp. pulchra (Cham.) Argus) and birch ( Betula nana L.) (twigs in winter, leaves in summer) were separately mixed at graded levels (0%, 20%, 40%, 60%, and 80%) with chopped hay ( Bromus inermis Leyss.) and fed as single meals to muskoxen. Meals containing ≥60% browse were often partially or completely rejected. Meals containing 20%–60% woody or leafy S. alaxensis or S. p. pulchra resulted in higher energy expenditure than meals of 100% hay. Meals containing 20%–60% woody B. nana tended to decrease energy expenditure relative to 100% hay, while 20%–60% leafy B. nana was similar to 100% hay. We conclude there is an energy cost associated with consuming browse. This cost varies by browse species and type. Since muskoxen tolerated up to 40% browse in the diet, this cost may be within their ecological tolerance. This tolerance has important implications under global warming scenarios.