Changes in the social behavior of urban animals: more aggression or tolerance?

Rafał Łopucki,Adam Kiersztyn,Daniel Klich

doi:10.1007/s42991-020-00075-1

Abstract

Behavioral traits play a major role in successful adaptation of wildlife to urban conditions. However, there are few studies showing how urban conditions affect the social behavior of urban animals during their direct encounters. It is generally believed that the higher density of urban populations translates into increased aggression between individuals. In this paper, using a camera-trap method, we compared the character of direct encounters in urban and non-urban populations of the striped field mouse Apodemus agrarius (Pallas, 1771), a species known as an urban adapter. We confirmed the thesis that urbanization affects the social behavior and urban and rural populations differ from each other. Urban animals are less likely to avoid close contact with each other and are more likely to show tolerant behavior. They also have a lower tendency towards monopolization of food resources. The behavior of urban animals varies depending on the time of day: in the daytime, animals are more vigilant and less tolerant than at night. Our results indicate that, in the case of the species studied, behavioral adaptation to urban life is based on increasing tolerance rather than aggression in social relations. However, the studied urban adapter retains the high plasticity of social behavior revealed even in the circadian cycle. The observation that tolerance rather than aggression may predominate in urban populations is a new finding, while most studies suggest an increase in aggression in urban animals. This opens an avenue for formulating new hypotheses regarding the social behavior of urban adapters.

Highlights

Wild terrestrial vertebrates under the pressure of urbanization are usually forced to use highly transformed and fragmented habitats and novel sources of food
Individual marking adapted to the camera trapping method has been used in very few studies (Łopucki 2007; Sollmann 2018). Assuming these restrictions, which applied to both urban and rural populations, we considered each encounter as an independent observation for which we were able to provide the following information: (1) time of occurrence of the encounter—based on sunrise and sunset over the period studied, we divided the encounters into daytime (7:00–15:59) and nighttime (16:00–6:59); (2) the duration of the encounter with an accuracy of one second; (3) behavior of the animals described using qualitative categories: aggression, tolerance, avoidance; (4) escape behavior of the individuals upon the encounter—we noted which individual was the first to escape from the observation point: the animal that appeared earlier or the one that appeared later
The encounters between the field stripped mice differed between the rural and urban populations, and the behavior of the rodent was dependent on the time of day

Summary

Introduction

Wild terrestrial vertebrates under the pressure of urbanization are usually forced to use highly transformed and fragmented habitats and novel sources of food They have to interact with constant anthropogenic disturbances and highly diverse stimuli and stressors, including vehicular traffic, human presence, pets, light pollution, and anthropogenic noise (Atwell et al 2012; Swaddle et al 2015; Weaver et al 2019). Given such a diverse set of evolutionarily novel factors affecting animals, only some wild species are able to adapt to city life (McKinney 2008; Francis and Chadwick 2012). For large and medium-sized mammals, e.g. bobcat Lynx

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