Browse Quality and the Kenai Moose Population

Abstract

The quality of moose (Alces alces) forage on the northwestern Kenai Peninsula, Alaska was evaluated by determining digestibility (as in vitro dry matter disappearance) and levels of fiber, protein, and minerals for 1 winter and 2 summer collections. There were significant changes in all parameters between summer and winter in the major browse species-paper birch (Betula papyrifera), aspen (Populus tremuloides), willow (Salix sp.), alder (Alnus sp.), and lowbush cranberry (Vaccinium vitisidaea) and significant differences among species within seasons. Considering all factors, alder and.willow ranked as the best summer browse plants and lowbush cranberry as the poorest; in winter, aspen and lowbush cranberry ranked best and paper birch poorest. However, since the different species provide different nutrients, sufficient quantities of all 5 species could better meet the needs of moose than any 1. The northern Kenai moose range, once multispecies habitat, is now dominated by paper birch; this is relatively poor winter forage, and the moose population is declining. J. WILDL. MANAGE. 41(3):533-542 The quality of plants that wild ungulates eat has been given little scrutiny. Yet, on both summer and winter range, quality is as important as quantity in maintaining healthy populations. In a study of moose forage Cowan et al. (1950) recognized the relationships between range quality, carrying capacity, and the successional stage of the forest. They noted specifically that fats (ether extracts), total carbohydrates, and proteins in the vegetation of a 6and a 20to 30-year-old forest were superior to those of a 70 plus-year-old forest; and that the most nutritious forage was found in the younger forests. Klein (1970) discussed the relationships between quantity of highquality plants and deer growth rate and body size, productivity and survival, and changes in age and sex ratio; he concluded that high-quality range is necessary for healthy deer populations. Dietz (1970) defined a high-quality plant as one that is palatable to the animal, has adequate levels of necessary nutrients in the proper ratios, has a high apparent digestibility, produces desirable proportions of volatile fatty acids, has adequate levels of minerals and vitamins, and is converted efficiently into components required by the consuming animal. Some researchers have looked at one or several of these components of quality, but no one has looked at all of them with respect to wild ungulates. This paper presents data we have collected to compare and define the quality of the important browse plants eaten by moose in summer and winter on Alaska's Kenai Peninsula. The characteristics we used to describe browse quality were: in vitro dry-matter disappearance (IVDMD), fiber content, protein content, and the concentration of 18 mineral elements. The study took place on the Kenai National Moose Range at the Kenai Moose Research Center, a cooperative research project of the Alaska Department of Fish and Game and the U.S. Fish and Wildlife Service. The Center is located in the northwestern lowlands of the Kenai Peninsula. About 40 percent of the lowlands were burned during a 125,455-ha fire in 1947. The land is rolling and covered by podsol soils that are glacially scoured and dotted with numerous lakes and bogs. Mature white J. Wildl. Manage. 41(3):1977 533 This content downloaded from 157.55.39.92 on Wed, 22 Jun 2016 05:11:59 UTC All use subject to http://about.jstor.org/terms 534 KENAI MOOSE BROWSE QUALITY -Oldemeyer et al. spruce (Picea glauca), paper birch, and aspen remain as islands within the burn. Regrowth consists mostly of black spruce (P. mariana), paper birch, willow and aspen, with paper birch producing over 80 percent of the annual browse production. The major shrubs of the unburned stands are aspen saplings and highbush cranberry (Viburnum edule). Ground vegetation in both the burned and unburned stands is dominated by lowbush cranberry, bunchberry (Cornus canadensis), rose (Rosa acicularis), twinflower (Linnaea borealis), and fireweed (Epilobium angustifolium). Although woody browse is poorest in quality of the year's food supply, it is the mainstay of the moose's winter diet. LeResche and Davis (1973) studied food selection by moose at the Kenai Moose Research Center and found that paper birch and lowbush cranberry were by far the most important species eaten during the winter on normally browsed range. Willow, aspen, alder, and dwarf birch (B. nana) are sparse and thus are not as important here as in interior Alaska (Coady 1973) or other parts of the range of moose (Peek 1974). We wish to thank V. L. Burton for in vitro and fiber analyses and G. R. Smith for crude protein determinations done at the Palmer Research Center of the University of Alaska, Institute of Agricultural Science. Parts of the study were financed by Federal Aid in Wildlife Restoration Project W-17-R. A. Loren Ward, Ann H. Jones, and Charles P. Stone critically reviewed the manuscript.