Effects of Hormonal and Social Factors Impacting Mating Behavior in Anurans: Lab, Field, and Computational Modeling Approaches

Social behavior in anurans is a complex system integrating internal physiological processes and external stimuli, and ultimately has crucial impacts on mating success. This research aimed to uncover both internal and external factors that have a potential impact on anuran social behavior using a combination of lab, field, and computational approaches. My first goal was to investigate an internal factor, the hormone leptin, as a possible regulator of calling behavior in anurans, due to its role in energy regulation and mating behavior in other taxa. Using immunohistochemistry in the brain of the African clawed frog, Xenopus laevis, I found leptin-like immunoreactivity in the pallium, striatum, and amygdala of the telencephalon, the preoptic area of the diencephalon, and in the thalamus and hypothalamus. I also administered leptin to calling gray tree frogs, Hyla versicolor, in the field, and observed a significant effect on call effort. These demonstrated that leptin could have a role in regulating vocalization. My second goal was to investigate external social factors that could affect spatial arrangement of male anurans and the quality of their calls in the field, using the recorded calls and spatial positions of Hyla versicolor from individual nightly choruses. In active choruses where males are clustered, males near the center of clusters displayed call characteristics preferred by females significantly more often than the other members of their clusters, suggesting that males use the social cues of other males and their positions in the chorus to make behavioral decisions. My third goal was to investigate potential rules of anuran behavior involving two factors hypothesized to drive social interactions: the amplitude of a call, and the number of pulses present in the call. I created a model in which male decision making and interactions were based primarily on amplitude-based rules of calling, movement, and position choice. Simulations from this model showed that male agents who began to call due to an amplitude-based rule produced clustered distributions compared to other rules, and that different neighbor preferences impacted the spacing within these clusters. I then used the design and findings from this to create another model, in which male position decisions and interactions, particularly competition and aggression, were primarily driven by pulse number. From these simulations, I found that while different neighbor preferences did not greatly impact the level of clustering, the behaviors within clusters were impacted, such that an intermediate number of aggressive interactions occurred when agents targeted neighbors based on pulse-number.