Use non-lethal methods to deter carnivores from attacking humans

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

  • Eight studies evaluated the effects of using non-lethal methods to deter carnivores from attacking humans. Three studies were in the USA, two were in Australia, one was in the USA and Canada, one was in Austria and one was in Bangladesh.



  • Survival (1 study): A study in Bangladesh found that when domestic dogs accompanied people to give advance warning of tiger presence, fewer tigers were killed by people.



Human-wildlife conflict (8 studies): Two studies, in the USA and Canada, found that pepper spray caused all or most American black bears and grizzly bears to flee or cease aggressive behaviour. One of these studies also showed that tear gas repelled half of American black bears. Two studies in the USA and Austria found that grizzly/brown bears were repelled by rubber bullets or by a range of deterrents including rubber bullets, chasing, shouting and throwing items. A study in the USA found that hikers wearing bear bells were less likely to be approached or charged by grizzly bears than were hikers without bells. A replicated, controlled study in Australia found that ultrasonic sound deterrent units did not affect feeding location choices of dingoes. A study in Bangladesh found that domestic dogs accompanying people gave advance warning of tiger presence, enabling people to take precautionary actions. A study in Australia found that a motorised water pistol caused most dingoes to change direction or speed or move ≥5 m away, but sounding a horn did not.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A study (year not stated) at campgrounds and garbage dumps in Minnesota and Michigan, USA (Rogers 1984) found that pepper spray repelled all American black bears Ursus americanus and tear gas repelled half of bears. Four out of five bears sprayed once in the eyes with pepper spray fled 7–20 m away and did not return. The fifth bear, a male, only fled after being sprayed four times (although on two occasions, the spray did not reach the bear’s eye). Four bears exposed to tear gas left the site. However, two returned within a few minutes. No animals exhibited signs of aggression. The study was conducted in sites (number not stated) where black bears were reported to be taking food from people. Five black bears were sprayed in the eyes with pepper spray from distances of 1.5–3.0 m and four were sprayed with tear gas.

    Study and other actions tested
  2. A study in 1980–1981 in forest in a national park in Wyoming, USA (Jope 1985) found that hikers wearing bear bells were less likely to be approached or charged by grizzly bears Ursus arctos. Of initially motionless bears spotted ≤150 m from hikers, a higher proportion (67%) moved away from hikers with bells than from hikers without bells (26%). No bears charged at hikers with bells, whereas 14% of bears spotted by hikers without bells charged at the hikers. Hikers reported 97 observations of bears within 150 m. In 24% of encounters, hikers wore bells. Human-bear encounters in a 154-km2 study area were surveyed from 3 June–15 September 1980 and 14 June–22 September 1981. Bell-wearing rates were assessed during timed counts of hikers on trails, at 15-day intervals. Hikers were questioned about bear encounters.

    Study and other actions tested
  3. A study in 1986–1989 at seven sites in two national parks dominated by temperate forest in Wyoming, USA (Gillin et al. 1994) found that using rubber bullets to scare problem grizzly bears Ursus arctos caused all bears to flee from study sites, at least for short period. Five bears were shot at using rubber bullets, 41 times in total, with 27 hits recorded and bears fled each time. Bears were generally deterred from returning to the study area for 2–4 weeks. However, two bears continued to exhibit nuisance behaviour and repeatedly exploited sources of human food. Rubber bullets were fired at bears that had been seeking human food or foraging close to habitation. Behaviour of each bear was noted before and after firing of bullets, as well as whether the bear fled from an area with a radius of approximately 100 m.

    Study and other actions tested
  4. A study in 1984–1994 across the USA (primarily Alaska and Montana) and Canada (primarily British Columbia and Alberta) (Herrero & Higgins 1998) found that after being sprayed with pepper spray, most brown bears Ursus arctos and American black bears Ursus americanus changed their behaviour. Fifteen out of 16 (94%) brown bears and all four (100%) black bears involved in close-range aggressive encounters with people changed the behaviour after being sprayed. However, in six cases (38%), brown bears continued to act aggressively and in three cases (19%) bears attacked the person spraying. Black bears did not leave the area after being spayed. Sixty-six records of bear-human interactions involving pepper spray use were collected from agencies throughout Canada and the USA and from individuals that used spray to deter bears. Results reported here are those involving close-range encounters with aggressive bears. Sprays used were thought to likely contain 10% capsicum extract.

    Study and other actions tested
  5. A study in 1995–2000 of seven animals across a mixed, but mostly forested, landscape in central Austria (Rauer et al. 2003) found that shooting rubber bullets, chasing, shouting and throwing items to reduce brown bears’ Ursus arctos habituation to humans was partially successful. After 16 aversive conditioning treatments on seven bears, they returned to the site of treatment within <1 day to >6 months. The time to their next observed habituated behaviour (being ≤50 m from an observer and behaving in an indifferent or curious manner) was one week to three years. Aversive treatments, some in combination, included five capture events, 11 discharges of rubber bullets, four uses of cracker shells and two of fireworks and warning shots. Bears were monitored through reported sightings and footprint tracking. Three bears were also tracked using radio-collars and ear transmitters, but these became detached from two bears.

    Study and other actions tested
  6. A replicated, controlled study (year not stated) on captive animals in Queensland, Australia (Edgar et al. 2007) found that ultrasonic sound deterrent units, tested as potential deterrents for dingoes Canis lupus dingo, did not affect feeding location choices. Dingoes first selected bait in front of one ultrasonic unit (unit 1 of two) on 21% of occasions when it was turned on. This did not differ significantly from the 29% of occasions that unit 1 was selected first when it was turned off and unit 2 was turned on. Four captive dingoes were housed in pens, opening onto a communal area. Two ultrasonic units (Weitech Yard and Garden Protector) were positioned back to back, with 5 g of tuna in front of each. One unit (selected randomly) was turned on. Dingoes, individually in random order, were released into the communal area, and bait selection order noted. Sixty such trials were conducted.

    Study and other actions tested
  7. A study in 2005–2007 in a mangrove area in Bangladesh (Khan 2009) found that domestic dogs Canis lupus familiaris accompanying people gave advance warning of tiger Panthera tigris presence, enabling people to take precautionary actions. Of the responses by dogs to apparent tiger presence 62% were verified as accurate. One tiger was killed by people during 2006 (within the study period), compared to 12 in the preceding four years (most of which was before the study period). Four humans were killed by tigers during 2006, compared to 75 over the preceding four years. Forty domestic dogs were each taken into the forest 18 times between August 2005 and January 2007. Each dog, tethered to a person, accompanied a group of 5–7 people (plant-product harvesters, honey gatherers or fishermen). Dogs responded to most wild animals with excitement, quick movements and vocalisations though apparent responses to tigers were fear and low noise and moving close to the owner without barking. Presence of tigers or other wild animals was verified immediately by observation, or the next day by locating pugmarks or scats.

    Study and other actions tested
  8. A study in 2015 at a beach in Queensland, Australia (Appleby et al. 2017) found that a motorised water pistol caused dingoes Canis dingo to display aversive responses (change direction or speed or move ≥5 m away) in most cases but sounding a horn did not. The water pistol produced more aversive responses (32 from 43 trials involving seven animals) than did blowing a whistle, a treatment assumed not to deter dingoes (one aversive response from 23 trials involving nine dingoes). The air horn produced no aversive responses in 13 trials involving six animals. Trials were conducted along a beach, in daylight, during 1–15 December 2015. With dingoes ≤5 m from an observer, a whistle was blown on the first trial, involving nine animals. For subsequent trials for these animals, the whistle was followed by sounding an air horn or firing a mechanical water pistol. Some trials for individual dingoes were repeated after short gaps (2–11 trials during 1–55 minutes).

    Study and other actions tested
Please cite as:

Littlewood, N.A., Rocha, R., Smith, R.K., Martin, P.A., Lockhart, S.L., Schoonover, R.F., Wilman, E., Bladon, A.J., Sainsbury, K.A., Pimm S. and Sutherland, W.J. (2020) Terrestrial Mammal Conservation: Global Evidence for the Effects of Interventions for terrestrial mammals excluding bats and primates. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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Terrestrial Mammal Conservation

This Action forms part of the Action Synopsis:

Terrestrial Mammal Conservation
Terrestrial Mammal Conservation

Terrestrial Mammal Conservation - Published 2020

Terrestrial Mammal Conservation

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