A disrupted human shield: the COVID lockdown alters carnivore dynamics in favour of a dominant competitor.

A 'human shield' effect occurs when a species associates with humans to avoid predators or competitors. Understanding how this effect shapes species interactions is critical as anthropogenic pressures increase globally. Despite broad theoretical support for this effect, its context-dependency remains unclear, especially in urban systems. We used the COVID-19 lockdowns as a natural experiment to separate the effects of the (static) human footprint and (dynamic) human recreational activity increases during lockdowns to test hypotheses related to a 'dynamic human shield' in a competitive species dyad (subordinate red foxes Vulpes vulpes and dominant coyotes Canis latrans) across an urban ecosystem. Three years of data (representing pre-lockdown, lockdown and post-lockdown periods) from >200 sites across 18 urban parks revealed dynamic responses to humans, but not in ways predicted by theory; the lockdown favoured the dominant competitor, which increased in relative abundance over time. Conversely, the subordinate species dynamically avoided humans and coyotes. These results suggest lockdown disrupted the human shield effect by favouring the dominant species, underscoring how human activity shapes species interactions.