Where do cougars hunt deer at the brightly lit wildland–urban interface?

Details

Artificial nightlight is increasingly recognized as an environmental disturbance affecting the habitats and fitness of many species, but its effects on wide-ranging vertebrates and their interactions remain unclear. Light pollution could amplify land-use change, making it important for conservation and land-use planning to understand how this sensory stimulant affects the behavior and habitat use of species valued for their ecological roles and economic impacts.

Across wildland–urban gradients in the southwestern United States, researchers combined satellite-derived estimates of light pollution with GPS data from 56 cougars (Puma concolor) and 263 mule deer (Odocoileus hemionus), as well as the locations of 1,562 deer carcasses killed by cougars. They assessed how light exposure related to mammal behavior and predator–prey relationships.

Deer used human-altered environments to access forage and were more active at night than deer in wildlands. Despite higher nightlight levels, cougars killed deer at the wildland–urban interface, but hunted in the relatively darkest locations. Light had the greatest effect of all covariates on where cougars killed deer at the interface.

Both species showed fine-scale responses to light pollution: individual cougars and deer with less light exposure increasingly avoided illuminated areas when exposed to greater radiance, whereas deer living at the wildland–urban interface selected areas with elevated light levels. The researchers concluded that incorporating light pollution estimates into ecological studies provides crucial insights into how the changing human footprint can alter animal behavior and ecosystem function across spatial scales.