The effect of visitors on the behavior of zoo‐housed western lowland gorillas (Gorilla gorilla gorilla)

Abstract

Primates, especially apes, are popular with the public, often attracting large crowds. These crowds could cause behavioral change in captive primates, whether positive, neutral, or negative. We examined the impact of visitors on the behavior of six western lowland gorillas (Gorilla gorilla gorilla), observing the troop over 6 weeks during high season (4.5 hr/day, 35 days, May-July 2016). We used focal scan sampling to determine activity budget and enclosure usage, and focal continuous sampling to identify bouts of anxiety-related behavior (visitor-directed vigilance, selfscratching, and aggression). Both daily zoo-entry numbers (V GATE) and instantaneous crowds at the exhibit (V DENSITY) were measured. Overall, V GATE had little effect across behaviors. However, consistent with the more acute time frame of measurement, V DENSITY was a better predictor of behavior; at high crowd volumes, we observed significant group-level changes in activity budget (increased inactivity, increased locomotion, and decreased environment-related behaviors), increase in some anxiety-related behaviors, and decreased enclosure usage. Although contributing similar effects, it could not be determined if crowd numbers, composition, or noise most affected the troop, nor any chronic effects of exposure to large crowds. Nevertheless, our findings suggest that measures to minimize the impacts of large crowds at the exhibit would be beneficial. Furthermore, we highlight potential discrepancies between common methods for measuring visitor numbers: V GATE is less sensitive to detecting visitor effects on behavioral indices than V DENSITY. Future studies should appropriately match the biological time frame of welfare indicators and visitor measures used to ensure the reliability of findings.

Behavioral Implications of the Complete Absence of Guests on a Zoo-Housed Gorilla Troop

“…Foraging behavior decreased in five of the six subjects when visitors were not in attendance; this is contradictory to several previous studies that observed a decrease in foraging when crowd sizes increased in zoo-housed gorillas [17] and chimpanzees [18], respectively. We also observed a general pattern of increased inactivity when visitors were absent, consistent with several other studies [19,21].…”

“…High crowd levels have been associated with a decrease in foraging behavior [ 17 , 18 ] and an increase in inactivity and resting behaviors [ 19 , 20 , 21 ]. Undesirable behaviors, such as overgrooming, plucking, regurgitation and reingestion (R/R), and pacing can increase with denser crowds [ 19 , 22 , 23 , 24 ].…”

Impacts of COVID-19 on Animals in Zoos: A Longitudinal Multi-Species Analysis

“…Previous research into the impacts of COVID-19 facility closures on zoo animal behaviour and enclosure usage has indicated variable behavioural responses [5]. Similar results are also reported in literature investigating HAIs in species during opening hours (e.g., sumatran orangutan (Pongo pygmaeus abelii) Bloomfield et al [13]; kangaroos (Macropus fuliginosus fuliginosus) and red kangaroos (Macropus rufus) Sherwen et al [14]; little penguins (Eudyptula minor) Chiew et al [15]; western lowland gorillas (Gorilla gorilla gorilla) Lewis et al [16]. Through this research we sought to expand on previous work [5] linked to zoo-closures to determine whether the variable behavioural responses to zoo closures during the COVID-19 pandemic were applicable across a wider subset of species.…”

'Bearly' Changing with the Seasons: Bears of Five Species Show Few Behavioral Changes Across Seasons and at Varying Visitor Densities

“…We evaluated two measures of visitor density as possible predictors of bear behavior: crowd size at the habitat during each observation, and the average attendance for the day of the observation. Some studies have suggested that counting visitors close to the habitat (as we did with our measure of crowd size) may provide a more sensitive prediction of behavior change than a broad measure of daily attendance (Kuhar, 2008;Lewis et al, 2020). Although we found limited differences between the two measures, this could be due to the limited differences we observed overall.…”

“…Several studies have reported changes in zoo animal behavior due to the presence of visitors, without concluding that these changes indicated any particular effect on animal welfare (Bennett's wallabies, Beaudin-Judd et al, 2019;gorillas, Kuhar, 2008;Lewis et al, 2020;Stoinski et al, 2012;kangaroos, Sherwen et al, 2015), or found no effect of visitor presence (anteater, Chiapero et al, 2020;chimpanzees and gorillas, Bonnie et al, 2016;greater rheas, Azevedo et al, 2012;meerkats, Sherwen et al, 2014). In some cases, other factors in the environment have been found to be better predictors of animal behavior, such as temperature, weather, or time of day (African penguins, Ozella et al, 2017;hornbills, Rose et al, 2020;ring-tailed lemurs, Goodenough et al, 2019;tigers, Goldsborough, 2017), all of which typically co-vary with visitor density.…”