Variation and conservation implications of the effectiveness of anti-bear interventions

Igor Khorozyan,Matthias Waltert

doi:10.1038/s41598-020-72343-6

Abstract

Human-bear conflicts triggered by nuisance behaviour in public places and damage to livestock, crops, beehives and trees are among the main threats to bear populations globally. The effectiveness of interventions used to minimize bear-caused damage is insufficiently known and comparative reviews are lacking. We conducted a meta-analysis of 77 cases from 48 publications and used the relative risk of damage to compare the effectiveness of non-invasive interventions, invasive management (translocations) and lethal control (shooting) against bears. We show that the most effective interventions are electric fences (95% confidence interval = 79.2–100% reduction in damage), calving control (100%) and livestock replacement (99.8%), but the latter two approaches were applied in only one case each and need more testing. Deterrents varied widely in their effectiveness (13.7–79.5%) and we recommend applying these during the peak periods of damage infliction. We found shooting (− 34.2 to 100%) to have a short-term positive effect with its effectiveness decreasing significantly and linearly over time. We did not find relationships between bear density and intervention effectiveness, possibly due to differences in spatial scales at which they were measured (large scales for densities and local fine scales for effectiveness). We appeal for more effectiveness studies and their scientific publishing in regard to under-represented conflict species and regions.

Highlights

Human-bear conflicts triggered by nuisance behaviour in public places and damage to livestock, crops, beehives and trees are among the main threats to bear populations globally
The species were biased towards American black bear and brown bear (χ2 = 42.737, df = 3, p < 0.001; Table 2) and intervention categories were dominated by aversion and husbandry (χ2 = 16.442, df = 4, p = 0.002), but there was no difference between intervention types (χ2 = 12.922, df = 11, p = 0.298)
Our study has demonstrated that husbandry interventions, especially electric fences, are most effective in protecting assets from bears (Fig. 1)

Summary

Introduction

Human-bear conflicts triggered by nuisance behaviour in public places and damage to livestock, crops, beehives and trees are among the main threats to bear populations globally. Description Yelling, aggressive sounds, discharging firearms, freon horns and bell collars Pepper spray, commercial repellents and chemicals Shocking devices, tree trunk barriers, rubber slugs, slingshots, stone throwing and chasing Concurrent application of several deterrents Fences with charged metal wires which produce electric shocks upon a contact Closed roofed (sheds) or open-air (corrals) structures to protect assets, usually at night Use of guarding dogs and llamas Concurrent application of several husbandry techniques Moving culprit bears away from conflict sites Selective or non-selective shooting of bears Herd management to shorten the calving period Keeping barbecue stuff out of reach, use of birdfeeders in cold season, and not feeding pets outdoors Food/garbage removal, use of bear-proof bins Replacement of sheep by cattle Provision of carrion, fruits or other food to avert from feeding on human assets Brush clearing, pruning and fruit harvesting include, but is not limited to, the isolation of food and garbage, calving control, vegetation care, change of human habits, livestock replacement, and supplemental feeding[22,23,24,25,26]. It seems most logical to assign electric fences to husbandry because they protect areas, shocking devices to physical deterrents as they target individual animals, and shock collars to invasive management as they are fixed on an animal neck

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