The impact of large carnivore population density on sheep and goat losses in Slovakia

Abstract

The population density of large carnivores is a crucial factor influencing livestock losses; however, existing research on this subject has produced conflicting results. Our study aimed to investigate the relationship between the population density of brown bears and Eurasian wolves and the resulting losses in sheep and goats due to these predators. We also compared the livestock losses caused by wolves and bears during a single attack. Our dataset comprised 1,285 wolf and 539 bear attacks recorded from 2007 to 2021. Over this period, wolves killed 6,286, and bears killed 1,345 sheep and goats. To assess the relationship between the mean density of large carnivores and the number of depredation events or combined sheep and goat losses, we employed a generalized linear model (GLM) with a log-link and a negative binomial error distribution. Additionally, we utilized a negative binomial generalized linear mixed model (GLMM) to compare differences in the mean number of animals killed per depredation event. Our results reveal an increase in sheep and goat losses and depredation events correlated with a consistent rise in wolf density. However, this pattern did not hold for bear density, as losses caused by bears significantly declined with an increase in their density. The mean number of sheep and goats killed per attack was higher for wolves (4.86) than for bears (2.48). Our research suggests that livestock damage may not necessarily escalate with an increase in the population density of predators, highlighting differences between wolves and bears.