Abstract
In the zoo environment, anthropogenic noise is common as sound levels fluctuate due to visitors, construction, habitat design, and special events. In this study, changes in the mood of three species of zoo-housed primates in response to a loud annual event were evaluated with the response-slowing paradigm. In this paradigm, animals experiencing anxiety slow responses on simple cognitive tasks when emotional content is displayed. Following a previously validated approach, we measured latencies to touch potentially threatening (conspecific faces with directed gaze) and non-threatening (conspecific faces with averted gaze) images overlaid on a grey square, relative to neutral control images (grey squares only) on a touchscreen. In Experiment 1, four Japanese macaques (Macaca fuscata) were tested in two conditions: during a baseline (non-stressful) period and opportunistically during three days during which loud jets frequently flew overhead. Results indicated a significant effect of condition, with an increase in latency to touch images of conspecific faces relative to control images during the days of the loud event. In Experiment 2, chimpanzees (Pan troglodytes, n = 4) and western lowland gorillas (Gorilla gorilla gorilla, n = 2) were tested during the same loud event following a similar methodology. The results revealed subtle changes across conditions; however, this was likely driven by the apes increasing their response speed to face stimuli relative to control stimuli over time (habituation). These findings suggest that the macaques, but not the apes, underwent detectable affective changes during the loud event. With additional development, this relatively simple paradigm may be an effective and feasible way to evaluate real-time changes in the mood of zoo-housed animals.
Highlights
Anthropogenic noise can influence animal behavior, physiology and well-being through effects on the auditory system, interference with sounds important to survival and reproduction, and generation of startle or fear-related responses (Blickley & Patricelli, 2010; Wright et al, 2007)
In Experiment 1, Japanese macaques demonstrated an increase in their latency to touch stimuli containing images of conspecific faces relative to control stimuli lacking conspecific faces during the days of a loud event
These findings suggest that the macaques experienced changes in affect during A&W
Summary
Anthropogenic noise can influence animal behavior, physiology and well-being through effects on the auditory system, interference with sounds important to survival and reproduction, and generation of startle or fear-related responses (Blickley & Patricelli, 2010; Wright et al, 2007). The authors found no such slowing effect following the veterinary exam for images containing averted (submissive) gaze faces Together, these findings suggest that response latencies to touch single images presented on a touchscreen may provide a measure of changes in affective state without the need for extensive training. In Experiment 1, we applied the response-slowing paradigm to test whether zoo-housed Japanese macaques (Macaca fuscata) experience changes in affect corresponding with a noisy, annual public event, the Chicago Air and Water Show (A&W) This event spans three days and is characterized by loud, lowflying jets intermittently passing directly over the macaques’ habitat. We hypothesized that the monkeys would experience anxious mood during the days of A&W and show an impairment (slower response time) on a simple cognitive task when emotionally threatening content is displayed, compared to a baseline period
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