Fluctuations in direct human presence, not predictable weekly cycles, influence avoidance behaviour in ravens.

Abstract

Background: Rhythms in human activity create patterns of opportunities and disturbances for wildlife, influencing their behaviour and spatial ecology. The weekend effect hypothesis posits that weekday-weekend routines in human activity can impact wildlife in creating cyclic conditions. At our study site - an outdoor wildlife park - free-flying ravens opportunistically exploit food intended for captive animals on a routine basis. While disturbances from visitor activity levels are typically low on weekdays and high on weekends, they can also vary day-to-day. Our access to data detailing visitor numbers makes our context well-suited to test whether ravens anticipate and respond to predictable weekday-weekend patterns following (1) a '5 + 2' structure, or if they respond (2) flexibly to fluctuations in direct human activity levels. By testing the weekend effect hypothesis from the perspective of a '5 + 2' pattern versus flexibly responding to fluctuations in human activity, we better understand wildlife response strategies to human activity.

Methods: Using long-term GPS tracking data, we investigated the weekend effect hypothesis by examining raven foraging probability and space use across two temporal scales: (1) daily patterns over five years, encompassing periods of Covid-19 pandemic-related restrictions, and (2) bihourly patterns over six weeks. We hypothesized that increased human activity levels would result in lower foraging probabilities and higher space use in ravens, varying between weekdays and weekends.

Results: Our findings provided limited support for the weekend effect hypothesis, considering a '5 + 2' pattern in human activity. However, ravens consistently avoided elevated human activity by decreasing in their probability of foraging at the site and increasing space use on a daily level.

Conclusions: Our study reveals that ravens are behaviourally flexible in their movement responses to disturbance when exploiting anthropogenically created foraging opportunities. Changes influencing anthropogenic resources and disturbances at resources should consider the potential knock-on effects to wildlife.