BLACK BEARS AS ANT-EATERS - SEASONAL ASSOCIATIONS BETWEEN BEAR MYRMECOPHAGY AND ANT ECOLOGY IN NORTH-CENTRAL MINNESOTA

We documented the seasonal occurrence and volume of different ant spec ies in black bear (Ursus americanus) seats in north-central Minnesota. We determined nest densities of common ant species in strip transects and compared their use by bears with their availability. We recorded phenologic change in ant-nest characteristics and measured the nutriti onal composition of ant workers, ant pupae, and herbaceous spring food s of bears. Consumption of ants was higher than reported elsewhere, pe aking in early July, when ants constituted 58% of seat volume and occu rred in 96% of seats. Increased consumption of ants in late spring coi ncided with (i) increased abundance and size of ant brood in nests and (ii) decreased protein and increased fiber levels in herbaceous foods . Lasius umbratus was the principal species consumed at I site, wherea s L. umbratus, Acanthomyops interjectus, and A. claviger dominated the diet farther south. These ants were likely preferred to other equally abundant species because of their sometimes dense concentrations insi de nests, passive behavior, and distinctive odor, enabling bears to fo rage more efficiently than on other species. We suspect that regional differences in ant consumption are due to differences in local availab ility of these species. Where they are less common, bears likely selec t large-bodied ants, usually Camponotus and Formica species.