Ants: A food source sought by Slovenian brown bears ( Ursus arctos )?

• Published in: Canadian Journal of Zoology
• Main Authors: Große, C, Kaczensky, P, Knauer, F
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2003
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Ursus arctos
• Online Access: http://dx.doi.org/10.1139/z03-151; http://www.nrcresearchpress.com/doi/pdf/10.1139/z03-151

In the heavily managed boreal forest of Scandinavia, ants, especially large colonies of red forest ants (Formica spp.), are abundant and brown bears (Ursus arctos) intensively feed on them. In contrast, the beech (Fagus sylvatica) forests of Slovenia provide only suboptimal habitat for ants and large ant colonies are virtually absent. To quantify how much ant use by brown bears is a matter of availability or preference, we quantified ant availability, species composition, and ant use. The estimated biomass of ants available to brown bears was very low in Slovenia compared with those in Sweden, averaging 135 vs. 9600 g/ha, respectively. Nevertheless, the frequency of occurrence of ants in Slovenian brown bear scats was high, averaging 85% and accounting for 25% of the ingested dry mass during the summer, which was nearly as much as their frequency of occurrence in Swedish brown bear scats during the summer. Although brown bears in Slovenia had year-round access to artificial feeding sites and the availability of ants is only about 1% of the biomass found in Sweden, they consumed about 50% of the quantity of ants compared with the brown bears in Sweden. Our results show that ants are an important and sought-after food source for brown bears in Slovenia, and the occurrence of ants should be considered in habitat-suitability models.