Bears and ants: myrmecophagy by brown bears in central Scandinavia

• Published in: Canadian Journal of Zoology
• Main Authors: Swenson, Jon E, Jansson, Anna, Riig, Raili, Sandegren, Finn
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1999
• Subjects: Ursus arctos
• Online Access: http://dx.doi.org/10.1139/z99-004; http://www.nrcresearchpress.com/doi/pdf/10.1139/z99-004

To determine general patterns of myrmecophagy in bears, we tested hypotheses regarding selection of ant species, factors important to bears when selecting ant species, factors influencing seasonal use of ants, and foraging behavior of brown bears (Ursus arctos) in central Sweden. Ants were an important food for these bears, constituting 12, 16, and 4% of fecal volume in spring, summer, and autumn, respectively. Ants were abundant, 30.5-38.5 tonnes per bear, and bears excavated 8-33% (mean 23%) of the mounds of red forest ants annually. Carpenter ants (Camponotus herculeanus) were highly preferred. Among mound-building red forest ants, the Formica aquilonia/polyctena complex was preferred over Formica exsecta and Formica lugubris. The ants selected by bears had high digestible energy and low formic acid content and behaved passively when the colony was disturbed. Colony size and density may also have influenced the selection of ants. Seasonal use of ants was related not to the availability of pupae or the quality of plant foods but probably to the availability of other foods. Bears consumed only a small proportion of the ants, 4000-5000, each time they opened a mound, probably because of rapidly increasing difficulty in capturing them after the colony was attacked. Eurasian brown bears feed more on ants than North American bears do, perhaps because of greater availability of large colonies of red forest ants. Carpenter ants may have been especially available in our study area following intensive clear-cutting.