Potentially negative ecological consequences of animal redistribution on beaches during COVID-19 lockdown

Abstract

Significant changes in the intensity or distribution of human activities, like during the 2020 COVID-19 lockdowns, can cause rapid changes to the diversity, distribution and abundance of animals. These changes are usually viewed as positive for ecosystems. Here, we mapped the abundance and habitat associations of coastal vertebrates along approximately 50 km of ocean beaches on the Sunshine Coast in eastern Australia using baited trail cameras before (April–June 2018 and 2019) and during the April–May 2020 COVID-19 lockdown. Many Torresian crows (Corvus orru) occur in urban areas where they scavenge for human-derived food. When this food source collapsed during the COVID-19 lockdown, Torresian crows moved to beaches where we recorded a 6-fold increase in abundance. Torresian crows principally moved to beaches with greater extent of remnant vegetation and larger average tree height. Because anthropogenic food sources would be less abundant on these more natural beaches, rapid changes in the abundance of these aggressive feeders on beaches could result in Torresian crows 1) outcompeting scavengers like large raptors for naturally occurring carrion, 2) consuming insects, crustaceans and other small animals (like small mammals and reptiles) along more natural coastlines, causing potentially significant changes to animal assemblage structure along beaches, and 3) depredating eggs and hatchlings from nests of other birds. Our results highlight that the ecological effects of changes to human pressures are nuanced, depending strongly on the functional role and behaviour of species and the landscape attributes in which they interact with the broader assemblages and ecosystem.