Songs of aggression : the singing mouse model

Social behavior is a vital part across vast taxa, from honey bees to elephants. This behavior is known to be modulated by nonapeptides acting on various nodes of the social behavior network (Newmann, 1999). Vasopressin and its evolutionary precursor vasotocin are both highly involved in the social brain. (De Vries and Panzica 2006; Goodson, 2005) Furthermore, it has been demonstrated that these systems are under the control of gonadal hormones (Bester-Meredith and Marler 2005). Here, we study the effects of hormones and experience on the social behaviors, specifically aggression, in the singing mouse Scotinomys teguina. These mice are known for their male stereotyped song used in territorial aggression as well as mate attraction. We gonadectomized the animals and coupled this with androgens at varying levels, or empty implants, to determine how gonadal hormones affect aggression and song. We discovered a significant increase in frequency of submission in animals following no hormone treatment, and a positive correlation with androgen level and physical aggression, as well as increase in propensity to sing. In a separate study, we also studied the singing response to social stimuli. We introduce the subjects to conspecific song, female bedding, and pink noise. We then recorded their responses following winning or losing encounters. We found animals increased their singing behavior in response to all stimuli following wins. Winning is known to increase aggression by allowing a transient increase in gonadal hormones. This study further bolsters the winner’s effect. Taken together, these experiments demonstrate in dynamic social behavior in a novel species that is modulated by hormonal states as well as social encounters.