Summer feeding and resting behaviour of wood bison and the effects of fire on fen vegetation near Waterhen, Manitoba

Abstract

Summer diets of a confined herd of wood bison, as indicated by fecal analyses, showed sedges and grasses to dominate each month, but vary in proportion of total plant composition. However, observations of the herd indicated that forbs were the dominant plants grazed, and were taken in successively decreasing proportions each month. Age-sex classes of bison did not differ in choice of plant species eaten during June, as indicated by observed behaviour. The classes differed in July, with cow diets differing from bull and spikehorn diets. Only bulls and spikehorns differed in August. Fire-treated sedge fens were little used by the bison because these areas were difficult to travel throuqh. In high-water fens, biomass of vegetation from burned fen was greater than fen only in June and July. Fire removed litter and allowed for rapid solar heating. The ash was thought not to provide a significant nutrient flush, as calcium content was more often less in burned fen sedges than in unburned ones. In addition, in low-water fen, biomass in burned fen was greater only in July. High-water fen always had greater vegetation biomass than low-water fen. Certain quality parameter suggested earlier maturation of vegetation in burned and high-water level fens. Resting habitats were chosen in different proportions between months in response to tabanid fly harassment. Open habitats were the dominant choices in June and July, but accounted for less than half the choices in August. Tabanid fly activity was greatest in June and July, and almost nil in August. The bison were thought to seek open habitats to escape these flies. The age-sex classes used habitats in different proportions during June and in July. Cows avoided open habitats, while spikehorns used open habitats the most. All classes used habitats in similar proportions during August. Feeding activity of the bison was crepuscular in June and July, but more diurnal in August. The increase in diurnal activity coincided with the decrease in tabanid activity.