Abstract
Eastern gray squirrels (Sciurus carolinensis) exhibit a variety of color morphs, including black. In the USA and UK, a common folk belief is that black squirrels are more aggressive than squirrels of other colors. We tested the biological basis of that belief using data from the 2018 Central Park squirrel census. Contrary to the belief, black squirrels do not chase other squirrels more often than do conspecifics of other colors. Black and non-black squirrels were equally likely to approach people for food and to display indifference to human presence, but black squirrels were more likely than non-black squirrels to flee from people. Although other research has found that aggression among squirrels increases when they live in higher population densities, black squirrels were no more aggressive than non-black squirrels despite the fact that they were sighted in parts of Central Park with higher squirrel population densities than other locations.
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The original dataset used in this research is available on New York City’s Open Data website (https://opendata.cityofnewyork.us).
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Notes
This refers to the Eurasian red squirrel (Sciurus vulgaris; Thorington et al. 2012, p. 73).
Ducrest et al. (2008) reviewed the literature on melanism’s associations with a variety of behaviors, including aggressiveness, and claimed to have found one mammal, the African lion (Panthera leo), in which melanism is associated with greater aggressiveness. However, the source they cite for that finding (West and Packer 2002) does not include any such finding. Instead, it points out that testosterone regulates both hair growth and melanin production and influences male aggression, although the source it cites for the finding on male aggression is about lizards, not lions (Marler and Moore 1988).
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Acknowledgements
We thank the organizers of the Central Park Squirrel Census and their many volunteer sighters for their hard work and for making their data publicly available. We also thank Beth L. Leech for advice about statistics.
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Both authors contributed to the study conception and design. Data analysis was performed by Lee Cronk. The first draft of the manuscript was written by Lee Cronk, and both authors commented on and edited previous versions of the manuscript. Both authors read and approved the final manuscript.
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Cronk, L., Palombit, R. Eastern gray squirrel (Sciurus carolinensis) color morphs do not differ in aggressiveness. acta ethol 24, 143–147 (2021). https://doi.org/10.1007/s10211-021-00372-z
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DOI: https://doi.org/10.1007/s10211-021-00372-z