Moose summer and winter diets along a large scale gradient of forage availability in southern Norway

Abstract

Studies on dietary functional responses in large herbivores are traditionally conducted by following individual animals. The method is very time-consuming, and hence, typically provides only a narrow array of forage species compositions. Here we use a range level approach to look at moose (Alces alces) selectivity for and utilization of forage species in relation to availability in both summer and winter. We compare 12 Norwegian ranges representing a large scale gradient in plant communities. The most important forage species in the diet were birches (Betula spp., comprising 43% of all trees browsed in summer and 27% in winter), rowan (Sorbus aucuparia, 25% of trees browsed in summer, 37% in winter), and bilberry (Vaccinum myrtillus, 42% of herbaceous epidermal fragments in summer feces). Selectivity for birches was positively related to its availability and negatively related to availability of rowan, Salix spp., and aspen (Populus tremula) together (all more selected for than birches). Multiple regression models including availability of several forage species were thus superior to single-species models in explaining the diet content of main forage plants. Selectivity for birches was also stronger in summer than in winter, while the opposite pattern was found for rowan. The finding is relevant for our evaluation of the quality of summer and winter ranges, and hence, their relative influence on population productivity. Our study underlines the need to incorporate species composition of available forage when quantifying dietary functional responses in selective herbivores such as moose. Furthermore, care should be taken when extrapolating data on moose diet across ranges or seasons.

Exclosures can favour natural regeneration of oak after conservation-oriented thinning in mixed forests in Sweden: A 10-year study

“…Gill and Beardall (2001) reported that browsing reduced species diversity and that tree species differed in susceptibility. In Scandinavia ash, aspen, rowan and sallow are highly preferred by browsers (Bergqvist et al, 2012;Edenius et al, 2011;Myking et al, 2013Myking et al, , 2011Wam and Hjeljord, 2010), whereas for instance birch is less preferred (Bergqvist et al, 2012;Wam and Hjeljord, 2010). We found that exclosures contained a higher proportion of tall saplings of ash, aspen and rowan, while the proportion of birch was higher in controls, indicating higher browsing effect on ash, aspen and rowan.…”

Fast and efficient DNA-based method for winter diet analysis from stools of three cervids: moose, red deer, and roe deer

“…The first method is feasible on a small group of animals only, and despite the immense work involved, it is not accurate in estimating the list and the amount of consumed species. During the observations of feeding traces along transects, it is often difficult to distinguish signs of use of the plants by different species of herbivores (Gębczyńska 1980; Wam and Hjeljord 2010). The analysis of the diet using microscopic examination is time consuming and requires appropriate training and an extensive reference database of food items (Holechek et al 1982).…”

“…For example, in Norway, the winter diet was predominantly rowan ( Sorbus aucuparia ), birch ( Betula spp. ), and pine ( Pinus sylvestris ), whereas pine was not found in the summer diet, instead the willow was browsed (Wam and Hjeljord 2010). In Sweden, the winter diet was dominated by pine and birch, while in summer, birch, willow, and herbaceous plants were most abundant (Cederlund and Nystrom 1981).…”

Interactions between ungulates, forests, and supplementary feeding: the role of nutritional balancing in determining outcomes

“…As a specialized browser, the preferred diet of moose throughout the growth season consists of selected green plant material, including the leaves of deciduous trees, shrubs, and herbs (Cederlund et al 1980;Rea et al 2014;Wam and Hjeljord 2010). During leaf-fall in the autumn, moose adjust their rumen physiology, metabolism, and food intake rates to adapt to a relatively nutrient poor and ligninrich winter diet of twigs and conifer needles (Hofmann 1989;Regelin et al 1985;Schwartz et al 1988).…”