The influence of human disturbance on wildlife nocturnality

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Science  15 Jun 2018:
Vol. 360, Issue 6394, pp. 1232-1235
DOI: 10.1126/science.aar7121

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  • Nocturnality decreases under low human disturbance conditions
    • Alejandro Martínez-Abraín, Lecturer, Universidade da Coruña
    • Other Contributors:
      • Daniel Oro, Research professor, Spanish Superior Council of Research

    Gaynor and collaborators (1) conducted recently a meta-analysis of 76 published studies, including 62 species from 6 continents, on the activity of medium and large-bodied mammals across gradients of human disturbance worldwide. Specifically they used as effect size (n=117) the ratio of the percentage of activity that occurs in the night in areas of high human disturbance over the percentage of nocturnality in areas of low human disturbance (Risk Ratio), measured on a logarithmic scale. They found an overall positive effect size of 36%. This means for example that if nocturnality has a value of 30% in low disturbance conditions, the value of nocturnality in high disturbance conditions increases to 41% as an average across study cases. The authors also conclude that temporal avoidance of humans may facilitate human-wildlife coexistence.
    Although we acknowledge that the meta-analysis is sound we think there is an alternative interpretation of their results that passed unnoticed to the authors. Centuries-old historical persecution of mammals all over the world pushed them to spatial refuges and to a nocturnal life. Hence, the by-default state now for many mammal species worldwide is nocturnality. The fact that the authors found a number of cases (those included in the lower left corner of Figure 1b) reflecting that under low human disturbance conditions nocturnality is low (e.g. lower than 50%) is by itself quite an achievement. It means that all over the world (i.e. no...

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    Competing Interests: None declared.

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