Food Patch Selection by the Largest European Herbivore - Testing Jarman-Bell Principle and Forage Maturation Hypothesis in Forest Habitats

The scaling relationship of digestive system with body mass shapes herbivore foraging strategies and resource selection. This association found its explanation among others in the Jarman-Bell principle and forage maturation hypothesis (FMH), which are two of the main predictions formulated in feeding ecology of herbivores. In this paper, we aimed at testing these predictions for the European bison which is the largest and sexually dimorphic European herbivore. We carried out our study in the Białowieża Primeval Forest, where European bison was recognized as refugee species. We estimated the quality and biomass of vegetation on the foraging paths of males and females of European bison and vegetation biomass at random points across different habitats and months. We did not find support for the Jarmann-Bell principle at intra-specific level in European bison as male and female forage on the selected patches did not differ in the crude protein and fiber (ADF) content and biomass.. The quality of vegetation on bison foraging patches expressed a significant spatio-temporal variation. It increased from May to July and then gradually decreased. It also increased with the fertility and wetness of habitats being the highest in wet forests. Mean biomass on European bison foraging patches (131.5 g/m2), was significantly lower than on random plots (210.5 g/m2), which supported the FMH. Our study indicated that in Białowieża Primeval Forest available rich food resources in summer may not constrain the metabolic rate/gut capacity ratio of both sexes which can potentially lead to diet segregation. Unlike in open habitats, where vegetation maturation is less temporally variable, in rich forest habitats, European bison may optimize their spatio-temporal patch selection and thus energy intake by tracking a habitat- and species-specific changes in the plant phenology. The understanding of the association between forage selection by European bison and forage nutritional constraints in forest habitats may be critical for conservation programs of this species as European bison is better adapted to more open habitats and recognised as refugee species in suboptimal forest habitats.