Ecological Research

, Volume 32, Issue 6, pp 931–941 | Cite as

Variations in aggression and activity levels amongst squirrels inhabiting low and high density areas

  • Amy Haigh
  • Ruth O’Riordan
  • Fidelma Butler
Original Article


Variation in an individual animal’s behavioural traits has been observed in a wide range of species and is believed to have important fitness consequences. As part of a larger study, it was observed that squirrels occurred at different densities on a 315 ha island, and this subsequently led to variations in faecal cortisol metabolite levels. This study aimed to examine whether living at different densities would also lead to variations in activity and aggression levels and in their survival probability, breeding and body condition. In order to examine variations in activity and aggression, behavioural tests (open field test, mirror image stimulation, breath rates and struggle rate tests) were conducted on 32 individuals (15♀, 17♂), a total of 69 times. Activity in the wild was investigated through radio tracking. There was a significant correlation between the time a squirrel was active and in their aggressive behaviour during the behavioural tests, with more aggressive individuals also being more active. Squirrels in the low density area spent a greater proportion of time active and engaged in aggressive behaviour in the open field test but also moved further in the wild and had a lower breath rate and higher struggle rates. Squirrels in the high density area were the least aggressive, had a smaller home range and higher breath and lower struggle rates. However, this was found to have no effect on survival probability, breeding or body condition. These variations may be the result of sampling dispersing squirrels.


Aggression Activity Home range Fitness Stress Tolerance 



This work was supported by The Irish Research Council, Enterprise Partnership Scheme and Fota Wildlife Park. The authors would like to extend a special thank you to Simon O’Hara of The Fota Resort, Sean McKeown and all the staff of Fota Wildlife Park and gardens and Emily Goldstein of University College Cork. The authors would also like to extend their gratitude to the anonymous reviewers, for their constructive comments, and improvements which they made to the manuscript.

Compliance with ethical standards


The study was funded by The Irish Research Council, Enterprise Partnership Scheme and Fota Wildlife Park Postdoctoral Fellowship (EPSPD/2012/313).

Conflict of interest

The authors declare that they have no conflicts of interest.

Ethical approval

All procedures performed involving animals were in accordance with the ethical standards of the institution at which the studies were conducted and with national guidelines.

Informed consent

Consent to submit has been received explicitly from all co-authors, as well as from Fota Wildlife Park where the work has been carried out.

Data availability

The datasets produced and analysed during the current study are available from the corresponding author on reasonable request.

Supplementary material

11284_2017_1506_MOESM1_ESM.docx (125 kb)
Supplementary material 1 (DOCX 125 kb)


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Copyright information

© The Ecological Society of Japan 2017

Authors and Affiliations

  1. 1.School of Biological, Earth and Environmental SciencesUniversity College Cork and Fota Wildlife ParkCorkIreland

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