Summer foraging on Scots pine Pinus sylvestris by moose Alces alces in Sweden ‐ patterns and mechanisms

Abstract

Scots pine Pinus sylvestris is a dominant winter food species to moose Alces alces in Fennoscandia but reports of its use during the growing season are limited. Browsing by moose on current‐growth, terminal shoots of Scots pine (CGTS) during summer was studied in three areas in southern and central Sweden to quantify this seasonal feeding habit. Dynamics of nutrient content in CGTS were also studied to relate the timing of consumption to the changing qualitative value of this forage. To determine the temporal pattern of browsing by moose, data were taken in young pine stands of two separate areas during the growing seasons of two different years, 1980 and 1995. In the former year use of terminal shoots peaked in mid‐June while in the latter year it peaked some two weeks earlier. Nutrient analyses, made only in 1995, showed that peak use of pine terminal shoots coincided with seasonal highs in magnesium (Mg), potassium (K), crude protein (CP), phosphorus (P), starch and total carbohydrates, and seasonal lows in acid detergent fibre (ADF) and acid detergent lignin (ADL). In vitro dry matter disappearance (IVDMD), a measure of digestibility, in terminal shoots in June was found to be significantly higher than in two other important moose browse species, birch Betula spp. and bilberry Vaccinium myrtillus. To determine frequencies of use of CGTS and heights of recently browsed trees, young pine stands in a third area were surveyed in July 1985. All browsed pine trees were between 30 and 230 cm in height, and 14% were browsed on some occasion during the growing season. Our results are discussed with respect to the potential mechanisms underlying summer use of CGTS by moose. Further research on the impact this feeding habit may have on forestry is suggested.