Influence of species-typical group size on social preferences and behavioral phenotype Open Access

Rosenberg, Ashley (Spring 2021)

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Background: Both individual and species differences affect how an animal engages in a social interaction. To inform neurological studies, it is essential to characterize species-typical behaviors, especially for newer model organisms, before looking at how certain neural mechanisms drive these behaviors. A characteristic of behavior that may be particularly informative for social behavioral phenotype is species-typical group size. For group living to evolve, animals may have evolved mechanisms that promote positive social interactions with conspecifics in various contexts - whether related to mating or not. Additionally, there may be a relationship between a drive to affiliate with larger groups and an affinity for novelty. After all, in large [non eusocial] groups, an animal is more likely to encounter novel conspecifics. Therefore, social neophilia may be an important trait for group-living species.

Purpose: The purpose of this project is to begin to identify species-typical social behavioral phenotypes and discern if species-typical group sizes in the wild will influence social preferences, such as a preference for affiliating with novel or familiar conspecifics.

Methods: To address how species-specific social phenotype influences social interactions, I compared two related species: the moderately social, small family-group living Mongolian gerbil and the highly social, large-group living African spiny mouse. I examined female spiny mouse and gerbil performance in a variety of social behavior tests and analyzed relationships between behaviors.

Results: A social interaction test revealed that while female spiny mice are more prosocial than aggressive, female gerbils are not significantly more prosocial than aggressive. However, female gerbils were significantly more aggressive than spiny mice. Spiny mice also spent significantly more time investigating and affiliating with a large group compared to a small group during a group size preference test, and exhibited more social boldness. Gerbils appeared more neophobic, spending significantly more time not interacting with stimulus animals during social preference tests.

Conclusion: These findings highlight that spiny mice may be particularly well-suited for studies of prosociality and gregariousness. Furthermore, principal components analysis revealed that spiny mice may have a highly flexible phenotype whereas for gerbils, social boldness, and not a propensity toward social novelty, may predict gregariousness.

Table of Contents

Introduction: 1-5 

Methods: 5-14

     Animals: 5-6

     Design: 6

     Cleaning Protocols: 6-7

     Behavioral Tests: 7-12

           Social Approach: 7

                Test Description: 7

                Ethogram: 7

            Social Interaction: 8-9

                Test Description: 8

                Ethogram: 9

            Social Preference: 10

               Test Description: 10

               Ethogram: 10

            Group Size Preference: 11-12

               Test Description: 11

               Ethogram: 12

      Statistics: 12

Behavioral Test Results: 13-19

      Social Approach: 13

      Social Interaction: 13-15

           Figures 1A and 1B w/Figure 1 Caption: 15

      Social Preference: 15-17

           Figures 2A and 2B w/Figure 2 Caption: 17

      Group Size Preference: 17-19

           Figures 3A and 3B w/Figure 3 Caption: 19

Behavioral Relationships: 19-29

      Principal Component Analysis for Female Gerbils and Female Spiny Mice: 19-22

           Table 1: Principal Components Matrix of Female Gerbil Behavior: 21

           Table 2: Principal Components Matrix of Female Spiny Mouse Behavior: 22

      Correlation: Neophobia in female gerbils: 23-24

           Figure 4 w/Figure 4 Caption: 24

           Figures 5A and 5B w/Figure 5 Caption: 24

      Correlation: Phenotypic consistency in female gerbils: 25

            Figure 6 w/Figure 6 Caption: 25

      Correlation: Neophobia aligns with anxious phenotype in female gerbils and spiny mice: 26-27

            Figures 7A, 7B and 7C w/Figure 7 Caption: 27

      Correlation: Quicker approach not associated with a drive to affiliate in female spiny mice: 28

            Figure 8 w/Figure 8 Caption: 28

      Correlation: Longer approach consistent with threat evaluation in female gerbils: 29

            Figure 9 w/Figure 9 Caption: 29

Discussion: 30-37

      Species-typical behavior: 30-33

            Social Approach: 30

            Social Interaction: 31

            Social Preference: 32

            Group Size Preference: 32-33

      Behavioral flexibility as evolutionarily adaptive: 33

      Personality/Behavioral Phenotype and Translational Implications: 34-36

      Future Studies: 36-37

Conclusion: 37

Contributions: 38

References: 38-43

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