Investigating the role of endogenous gonadal hormones in territorial exploration

Abstract

Past research and evidence have demonstrated how hormones and the environment interact with one another to produce an animal’s behavioral display. However, most of these studies investigate the influence of hormones and environment on behavior in social interaction contexts. Even when mice are alone, there are still many social sensory cues present within the environment that could influence the mouse’s behavior, such as urine. The goal of this thesis was to investigate the role of endogenous hormones in solo, territorial exploration in both male and female mice. This was accomplished by tracking animal pose of male and female mice while they were in home and novel cage conditions. There were three different types of novel environments where the cage could belong to one of three strains of mice: CD-1 male, CD-1 female, and BALB/c male. Probability density histograms were produced for each behavioral session, and these were compared pre- and post-gonadectomy to observe how behavior changes as a result of loss of endogenous hormones. Unsupervised behavioral quantification revealed that endogenous hormones have an influence over solo, exploratory behavior in both males and females. However, this effect is sex- and context-dependent. For males, endogenous hormones had a significant influence over solo, exploratory behavior in environments where a female had been present compared to the other cage conditions. For females, endogenous hormones had a significant influence over solo, exploratory behavior in the home cage. Interestingly, females’ territorial exploration changed more than males after the removal of endogenous hormones. Future research can investigate what specific types of behaviors change after removing endogenous hormones, since these changes appear to be sex-specific. Additionally, this study should be replicated including oscillatory motion in the tracking model and perhaps using wavelet spectrograms to construct the behavioral density maps. Overall, this study can act as the basis for future research investigating the effects of endogenous hormones over solo behaviors based on the hormonal and social context of the animal.