Does seasonal variation in forage quality influence the potential for resource competition between muskoxen and Peary caribou on Banks Island?

Nicholas C Larter,David S Hik,John A Nagy

doi:10.7557/2.22.2.1533

Abstract

Inter- and intra-annual variation in forage quality may influence population dynamics of Peary caribou and muskoxen on Banks Island. From 1993 to 1998 we collected 300 composite samples of sedge (Carex aquatilis and Carex spp.), willow (Salix arctica), legume (Oxytropis spp. and Astragalus spp.), and avens (Dryas integrifolia). Samples were collected in mid-June (start of the growing season), mid-July (peak of the growing season), mid-late August (senescence), and early (November), mid- (February), and late- (April/May) winter. We analysed forages for percent digestibility (in vitro acid-pepsin dry matter digestibility), crude protein (CP), fibre, lignin, and energy content. There was significant inter-annual variation in levels of lignin, fibre, and energy, and significant intra-annual (seasonal) variation for all quality measures and forages, which reflected the strong difference in quality between summer and winter. We discuss the relationship between forage quality and seasonal diet composition of Peary caribou and muskoxen, and the potential implications for the reduced Peary caribou and high muskoxen populations.

Highlights

Peary caribou (Rangifer tarandus pearyi) and musk- Nagy, 2001b), but intra- and inter-annual differoxen (Ovibos moschatus) are the two dominant resi-ences in forage quality and availability may be condent large herbivores on Banks Island
In this paper we report seasonal and annual Island can be found in Wilkinson et al (1976), (1993-1998) changes in crude protein, digestibility, Porsild & Cody (1980), and Zoltai et al (1980)
Mean (s) fibre (%), lignin (%), percent digestibility, crude protein, and energy content of six for¬ ages sampled during the start of, the peak of the growing season, and senescence

Summary

Introduction

Peary caribou (Rangifer tarandus pearyi) and musk- Nagy, 2001b), but intra- and inter-annual differoxen (Ovibos moschatus) are the two dominant resi-ences in forage quality and availability may be condent large herbivores on Banks Island. We determined lignin and fibre content for Salix, legume, Dryas, live summer C. aquatilis, and winter C. aquatilis samples only. Statistical analyses For the purposes of statistical analysis we pooled forage quality measures across both sample areas, based on the rationale provided by Larter & Nagy (2001a), and partitioned sampling time into three summer (June, July, August) and three winter (November, February, April) periods.

Results

Conclusion