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Nocturnal refuge
As the human population grows, there are fewer places for animals to live out their lives independently of our influence. Given our mostly diurnal tendencies, one domain that remains less affected by humans is the night. Gaynor et al. found that across the globe and across mammalian species—from deer to coyotes and from tigers to wild boar—animals are becoming more nocturnal (see the Perspective by Benítez-López). Human activities of all kinds, including nonlethal pastimes such as hiking, seem to drive animals to make use of hours when we are not around. Such changes may provide some relief, but they may also have ecosystem-level consequences.
Abstract
Rapid expansion of human activity has driven well-documented shifts in the spatial distribution of wildlife, but the cumulative effect of human disturbance on the temporal dynamics of animals has not been quantified. We examined anthropogenic effects on mammal diel activity patterns, conducting a meta-analysis of 76 studies of 62 species from six continents. Our global study revealed a strong effect of humans on daily patterns of wildlife activity. Animals increased their nocturnality by an average factor of 1.36 in response to human disturbance. This finding was consistent across continents, habitats, taxa, and human activities. As the global human footprint expands, temporal avoidance of humans may facilitate human-wildlife coexistence. However, such responses can result in marked shifts away from natural patterns of activity, with consequences for fitness, population persistence, community interactions, and evolution.
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