More Animals Are Becoming Nocturnal Thanks to Human Activity

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If you’re a human-wary animal living near humans, what do you do?  For some animals, the answer is to become more nocturnal.  Researchers from UC Berkeley undertook a study that looks at the effect of human activity on the daily activity patterns of wildlife.  The researchers looked at data collected from 72 studies about 62 herbivore and carnivore species larger than 1 kilogram across six continents.  This data came from GPS trackers, radio collars, remote triggered cameras, and in situ observations.

Case studies highlighting the influence of human activity on nocturnal shifts in animal behavior. Figure: Gaynor et al., 2018.

Case studies highlighting the influence of human activity on nocturnal shifts in animal behavior. Figure: Gaynor et al., 2018.

The researchers looked at the movement patterns of these animals and analyzed how diurnal variations differed between populations living in areas with both high and low human-related activities. The study found that animals liver near to human populations were more likely to increase the ratio of nighttime activities compared to animals living in low human density areas.  An animal that normally spent 50% of its activity at night tended to increase that percentage of activity to 68% in higher human activity areas. The researchers found that this pattern held true regardless of human activity such as hunting, hiking, mountain biking, and infrastructure such as roads, residential settlement, and agriculture.

“While we expected to find a trend towards increased wildlife nocturnality around people, we were surprised by the consistency of the results around the world,” said Berkeley PhD candidate and study lead author Kaitlyn Gaynor. “Animals responded strongly to all types of human disturbance, regardless of whether people actually posed a direct threat, suggesting that our presence alone is enough to disrupt their natural patterns of behavior.”

A) Location of the 72 studies used to analyze animal activity B) Graph showing the relative change in nocturnal activity near human disturbance. Figure: Gaynor et al., 2018

A) Location of the 72 studies used to analyze animal activity B) Graph showing the relative change in nocturnal activity near human disturbance. Figure: Gaynor et al., 2018

The study

Gaynor, K. M., Hojnowski, C. E., Carter, N. H., & Brashares, J. S. (2018). The influence of human disturbance on wildlife nocturnality. Science, 360(6394), 1232-1235.

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