We documented the seasonal occurrence and volume of different ant species in black bear (Ursus americanus) scats 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 nutritional composition of ant workers, ant pupae, and herbaceous spring foods of bears. Consumption of ants was higher than reported elsewhere, peaking in early July, when ants constituted 58% of scat volume and occurred in 96% of scats. Increased consumption of ants in late spring coincided 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 1 site, whereas 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 inside nests, passive behavior, and distinctive odor, enabling bears to forage more efficiently than on other species. We suspect that regional differences in ant consumption are due to differences in local availability of these species. Where they are less common, bears likely select large-bodied ants, usually Camponotus and Formica species.
Towards precision ecology: Relationships of multiple sampling methods quantifying abundance for comparisons among studies