Bears and ants: myrmecophagy by brown bears in central Scandinavia

Abstract

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.

Distribution of Mound-Building Ant Species (Formicaspp., Hymenoptera) in Finland: Preliminary Results of a National Survey

“…Further, they are important resource for both invertebrates and vertebrates (e.g. Lehtinen 1987, Gösswald 1990, Elgmork & Kaasa 1992, Swenson et al 1999, Päivinen et al 2002, they play an important role in soil bioturbation (e.g. Pokarzhevskij 1981), in cycling and relocating carbon and nutrients (e.g.…”

Predation on Moose Calves by European Brown Bears

“…In the European boreal forest ecosystems, brown bears commonly consume vegetable matter, insects, and ungulates, with the importance of vertebrate meat increasing with latitude (Vulla et al 2009). Studies of brown bear diet, based on scat studies or foraging sign, have been conducted in four areas of Scandinavia, (Haglund 1966, Elgmork and Kaasa 1992, Dahle et al 1998, Swenson et al 1999, Persson et al 2001), but have not described the annual variation in diet or food resources.…”

“…(Dahle et al 1998, Swenson et al 1999, Persson et al 2001). In addition, brown bears frequently utilize bait and slaughter remains at dump sites (Steyaert et al 2014).…”

The ant (Hymenoptera: Formicidae) communities of the central interior of British Columbia: Adaptations to a temperature-constrained environment.

“…Although ants appear to be able to utilize a broad range of woody debris sizes and decay classes, it is clear that large pieces are preferred by many species, especially those forming larger colonies (e.g., C. herculeanus and F. aserva). Thus the retention of larger pieces of woody debris should be a management objective as ants are ecologically important from a number of perspectives (e.g., as food for 105 bears (Noyce et al 1997;Elgmork and Unander 1999;Swenson et al 1999) and birds . Although the CWD volumes encountered in our study appear adequate for use by the ant fauna, concerns may arise from any significant reduction in postharvest CWD volumes.…”

“…In addition to pest control (Finnegan 1974;Torgersen and Mason 1987;Way and Khoo 1992), these include soil-nutrient turnover (Wagner et al 1997), seed dispersal (Heithaus 1981;Gorn et al 2000), grain consumption (Brown et al 1979), and decomposition of organic material (Haines 1978). Ants have also been found to be an important food source for birds and large omnivorous vertebrates such as black (Noyce et al 1997) and grizzly bears (Elgmork and Unander 1999;Swenson et al 1999).…”