Brown bear foraging ecology in Slovenia

Female brown bear in Jurjeva dolina, Javorniki-Sneznik mountain range, Slovenia. Photo credit: Alojz Skvarca

Anthropogenic food sources are often freely available to brown bears (Ursus arctos) in many parts of the world, including parts of densely inhabited Europe. Such human-derived foods are fed to bears by people both intentionally (e.g., diversionary feeding of grains) and unintentionally (e.g., human food and trash, agricultural crops). Bears that forage for anthropogenic foods often have higher reproductive and mortality rates when compared to conspecifics. It has also been shown that bears that are habituated to human-use areas and/or conditioned to forage for human foods and trash are often in conflict with people or their property. Bears involved in conflicts are often killed by people, which is currently recognized as one of the most critical threats to brown bear conservation worldwide.

The Republic of Slovenia is home to one of the highest densities of brown bears in the world (up to 40 bears/100 km2). A majority of the bear population in Slovenia (N=500-700) occurs in a small geographic area (~5,000 km2) in the human-dominated Dinaric mountains. For the past century, bears in Slovenia have been fed corn and livestock carrion intentionally at hundreds of feeding sites. Feeding of bears is widely used in the region to control population numbers (bating for hunters) and to mitigate human-bear conflicts (diversionary feeding). Similar to other areas in the world, a large proportion of human-bear conflicts in Slovenia are likely related to bears becoming conditioned to forage for human foods and trash, crops, and other anthropogenic foods. Interestingly, it appears that diversionary feeding decreases the level of conflicts in the region.

Brown bear feeding on corn from an automatic feeder. Photo credit: Miha Krofel

Slovenia is an ideal site for studying human-bear conflict and understanding the impacts of managing bears with diversionary feeding. To prevent future conflicts in Slovenia, we need to understand how this undesirable behavior develops in populations. To achieve our goal, we must gain a comprehensive understanding of brown bear foraging ecology in Slovenia, which is the focus of our work.

Main questions:

  • To what extent do brown bears in Slovenia forage for different anthropogenic food sources?
  • What effect does foraging for anthropogenic foods have on the life-history, behavior, health, and fitness of bears?
  • How do brown bears develop conflict behavior?

Objectives:

We will use a large database of tissues (muscle, liver, hair, and teeth) sampled from ~800 bears harvested by hunters or lethally removed by the Slovenia Forest Service to carry out the following:

    • Use stable isotopes to reconstruct the seasonal diets of bears since 1995.
    • Quantify the importance of anthropogenic foods to bears (different age-classes, sexes, and behaviors) through time and relate these measures to a variety of geographical, environmental, and ecological covariates (including natural food availability).
    • Measure the effects of corn-foraging on body condition, reproduction, mortality rates, and movements of bears.
    • Use diet information, genetic data, and management records to determine the primary mechanism(s) responsible for the development of conflict behavior in bears.

 

This research is part of a larger project financed by Slovenian Research Agency (grant number J4-7362), managed by Dr. Klemen Jerina, and led by Ph.D. candidate, Jernej Javornik (right).