Inducing fear using acoustic stimuli—A behavioral experiment on moose (Alces alces) in Sweden

Abstract

Prey species may display anti‐predatory behavior, i.e., flight, increased vigilance, and decreased feeding, in response to the true presence of a predator or to the implied presence of a predator through, e.g., acoustic cues. In this study, we investigated the anti‐predatory reactions of moose ( Alces alces ) to acoustic stimuli related to hunting, at saltlick stones, a known attractant. In before‐during‐after‐control‐impact experiments, we compared the behavioral responses of individuals to: (i) two hunting‐related acoustic stimuli—hunting dog barking and human speaking; (ii) nonpredatory acoustic stimuli—bird sounds and; and (iii) no acoustic stimulus (control). We asked: (1) How does the probability of moose leaving the site differ depending on the stimulus they are exposed to?; (2) What affect do the acoustic stimuli have on the amount of time moose spend vigilant, feeding, or away from the site?; and (3) What affect do the stimuli have on the time between events at a site? We found that when exposed to the human stimulus, moose left the sites in 75% of the events, which was significantly more often compared to the dog (39%), bird (24%), or silent (11%) events. If moose did not leave the site, they spent more time vigilant, and less time feeding, particularly when exposed to a dog or human stimulus. Furthermore, moose spent the most time away from the site and took the longest to visit the site again after a human stimulus. Moose were also more likely to leave the site when exposed to the bird stimulus than during silent controls. Those that remained spent more time vigilant, but their behaviors returned to baseline after the bird stimulus ended. These findings suggest that acoustic stimuli can be used to modify the behavior of moose; however, reactions towards presumably threatening and nonthreatening stimuli were not as distinct as we had expected.

Fear of the human ‘super predator’ in native marsupials and introduced deer in Australia

“…giraffe, leopards, hyena, zebra, rhinoceroses and elephants; n = 19 species) in Greater Kruger National Park ran more or fled faster on hearing humans compared to hearing lions, being on average twice as (2.0 times more) likely to run from humans than lions [16]. This effect size closely accords with the median likelihood of fleeing more or faster (2.1 times; range = 1.4-5.0) on hearing humans compared to hearing leopards, cougars, bears, dogs or wolves, demonstrated in comparable experiments on diverse carnivores and ungulates (cougars, European badgers, fallow deer, moose, white-tailed deer, wild boar) in Asia, Europe and North America [12,[17][18][19][20][21].…”

“…Our results demonstrate that native marsupials in Australia are not naïve to the danger posed by the human 'super predator'. As with the marsupials we tested in Tasmania, dogs are presently [16,20,35,37], or have been in the recent past [12,[17][18][19], used to hunt the species included in most of the previous playback experiments testing fear of humans, which is why most have tested responses to dogs. Dogs are thus a threat, but as corroborated by the significantly greater fear of humans than dogs that our results demonstrate in correspondence with those from all prior comparable experiments, wildlife worldwide evidently recognize that it is humans who are the largest source of danger [13][14][15][16].…”

“…Playbacks were standardized to a volume of 60 dB at 10 m so that they were audible, but not startling, to animals within the 15 m detection range of the camera's motion sensor [16,19,52,53]. As in previous ABR experiments, we placed bait (5 kg of 'Stock nuts', Laucke Mills, Greenock, South Australia) 10 m in front of the ABR as an attractant to maximize the number of reactions captured and help ensure that the animal's position meant the reaction was readily quantifiable [9,[18][19][20]32].…”

“…To quantify fear we evaluated (i) whether animals fled in response to the playback [1,16] and (ii) the percentage of time they spent vigilant if they did not flee [52,53]; on their first exposure to a playback treatment in each 'independent exposure bout' (defined below). Fleeing is among the most straightforward behavioural measures of fear [1], and being readily recognizable in virtually all species [16,53], it has been used to gauge the relative fear of humans in all prior comparable experiments [9,12,[16][17][18][19][20][21]. Vigilance, in contrast, is often difficult to compare between species [53] and it is not uncommon that prey that show strong differences in the likelihood of fleeing from different predators are similarly vigilant to all predators [20,52,53].…”

“…Fleeing is among the most straightforward behavioural measures of fear [1], and being readily recognizable in virtually all species [16,53], it has been used to gauge the relative fear of humans in all prior comparable experiments [9,12,[16][17][18][19][20][21]. Vigilance, in contrast, is often difficult to compare between species [53] and it is not uncommon that prey that show strong differences in the likelihood of fleeing from different predators are similarly vigilant to all predators [20,52,53]. Vigilance can nonetheless be useful in revealing different levels of fear toward different predators in species with a low natural proclivity to flee [17,52,54].…”