Influence of face masks on the flight responses of North American wildlife during the COVID-19 pandemic

Background/Question/Methods

COVID-19 caused a rapid shift in human behavior with the widespread use of masks to limit pathogen spread. This shift provides a unique opportunity to understand wildlife responses to changes in human behavior. A study conducted in China found that Eurasian tree sparrows shorten flight initiation distance (FID) in response to mask-wearing, whereas another study in Europe found FID of 32 bird species was not associated with mask-wearing. FID, or the distance at which a behavioral escape is initiated, indicates risk perception, with longer FIDs indicating a higher risk sensitivity. In 2020-2021, student groups associated with Squirrel-Net used a standardized protocol to measure FID in five North American wildlife groups (ground squirrels, tree squirrels, gulls, deer, and songbirds), along with multiple habitat covariates. Using these data, we tested competing hypotheses about the relative importance of masks vs habitat factors on animal risk perception with generalized linear mixed models. For each wildlife group, our model set consisted of each individual predictor, two-way combinations of predictors, and a global model. We then constructed a second model set consisting of the top models from the first set with mask-wearing as an additional predictor. Models were compared using Akaike’s Information Criterion (AICc).

Results/Conclusions

The use of masks did not affect FID for any of our study species. Across all five taxonomic groups, our models highlighted the importance of measured habitat covariates, such as time of day and presence/absence of conspecifics, while consistently showing little support for models that included mask-wearing. Our results indicate that for these North American taxa, anti-predatory escape behavior is not influenced by mask-wearing, but rather by environmental factors and life history traits. Therefore, as mask mandates are eased, unmasking should not influence perceived risk of predation in our study groups. Our study also highlights the value of including undergraduate students in professional research. Providing this kind of networked undergraduate research opportunity allows students to engage in the scientific process while rapidly collecting a useful dataset from across a large geographic region.