Alyson M. Andreasen | Search USGS

USGS2026

Extreme droughts shrink suitable habitats and reduce fitness for large mammals in the American West

Droughts are intensifying across the biosphere, yet the consequences of this phenomenon for wildlife habitat suitability and fitness are poorly studied. We analyzed 12 years of GPS telemetry data for three large mammal species—herbivorous mule deer ( N = 2854), omnivorous black bears ( N = 103), and carnivorous cougars ( N = 105)—to evaluate the effects of drought on each species’ habitat selection across a 500,000-km 2 aridity gradient in the interior West, USA. Additionally, we evaluated interannual variation in mule deer reproduction as a function of drought intensity. Severe drought reduced the area of highly selected habitat by 10.0% for mule deer, 14.3% for black bears, and 18.2% for cougars, suggesting stronger negative effects of drought at upper trophic levels. We also found that mule deer fawn recruitment decreased by >34% under extreme drought conditions. Our findings highlight the critical influence of drought on habitat selection of large mammals and common indices of mule deer fitness. Furthermore, we underscore the need for integrating predictions of climate-driven environmental changes into wildlife conservation planning.

Communications Earth & Environment↗

USGS2020

Artificial nightlight alters the predator-prey dynamics of an apex carnivore

Artificial nightlight is increasingly recognized as an important environmental disturbance that influences the habitats and fitness of numerous species. However, its effects on wide‐ranging vertebrates and their interactions remain unclear. Light pollution has the potential to amplify land‐use change, and as such, answering the question of how this sensory stimulant affects behavior and habitat use of species valued for their ecological roles and economic impacts is critical for conservation and land‐use planning. Here, we combined satellite‐derived estimates of light pollution, with GPS‐data from cougars Puma concolor (n = 56), mule deer Odocoileus hemionus (n = 263) and locations of cougar‐killed deer (n = 1562 carcasses), to assess the effects of light exposure on mammal behavior and predator–prey relationships across wildland–urban gradients in the southwestern United States. Our results indicate that deer used the anthropogenic environments to access forage and were more active at night than their wildland conspecifics. Despite higher nightlight levels, cougars killed deer at the wildland–urban interface, but hunted them in the relatively darkest locations. Light had the greatest effect of all covariates on where cougars killed deer at the wildland–urban interface. Both species exhibited functional responses to light pollution at fine scales; individual cougars and deer with less light exposure increasingly avoided illuminated areas when exposed to greater radiance, whereas deer living in the wildland–urban interface selected elevated light levels. We conclude that integrating estimates of light pollution into ecological studies provides crucial insights into how the dynamic human footprint can alter animal behavior and ecosystem function across spatial scales.

Arizona, California, Colorado, Idaho, Nevada, New ↗