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Effects of the social environment on the behaviour and fitness of a territorial squirrel

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Title: Effects of the social environment on the behaviour and fitness of a territorial squirrel
Author: Siracusa, Erin
Department: Department of Integrative Biology
Program: Integrative Biology
Advisor: McAdam, Andrew
Abstract: Most organisms interact with conspecifics and therefore have a social environment. While it is understood that variation in the composition of this social environment can have important consequences for gregarious species, solitary, territorial species may also live in socially complex environments where the composition of neighbouring conspecifics can directly influence time and energy spent on territory defence. The importance of the social environment for solitary species is, however, poorly understood. In this thesis, I combined behavioural observations, field experiments, and long-term data analysis from a population of North American red squirrels (Tamiasciurus hudsonicus) to explore the effects of the social environment on the territorial dynamics, behaviour and fitness of an ‘asocial’ species. In particular, I looked at two aspects of the social environment that were likely to have important effects on territorial species: familiarity and relatedness with neighbours. In my first chapter, I established that squirrels living in social neighbourhoods with high average familiarity faced reduced risk of intrusion and cache pilferage from conspecifics, providing evidence of the ‘dear-enemy’ phenomenon in red squirrels. In Chapter 2, I experimentally demonstrated that red squirrel ‘rattle’ vocalizations serve an important territorial defence function by deterring conspecifics from intruding. In Chapter 3, I found that red squirrels respond to changes in their social environment by adjusting their behaviour in a manner that reduces the costs of territoriality: in familiar social neighbourhoods red squirrels reduced their rattling rates and increased the proportion of time spent in nest. Finally, in Chapter 4, I used 21 years of data to show that living near familiar neighbours has substantial fitness benefits, increasing annual reproductive success and survival in both male and female squirrels. Collectively my thesis contributes to our broader understanding of the importance of the social environment for ‘asocial’ species and provides evidence that interactions between territorial individuals are not strictly competitive but can also be cooperative in nature. In particular, mutualistic interactions, rather than kin-selection, were important in mitigating conflict and enhancing fitness. Studying social interactions in asocial animals may, therefore, provide important insights into the mechanisms driving the evolution of social systems.
URI: http://hdl.handle.net/10214/14298
Date: 2018-09
Rights: Attribution-NonCommercial-NoDerivs 2.5 Canada


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