Available at: http://digitalcommons.calpoly.edu/theses/1290
Date of Award
MS in Biological Sciences
Behavior may be dramatically influenced by changing environments, and differences in light intensity environments may have important behavioral consequences. One approach to understanding changes in behavior is by studying behavioral syndromes, suites of correlated behaviors reflecting between individual consistencies in behavior expressed within a behavioral situation (e.g., correlations between antipredator behaviors in different habitats), or across behavioral contexts (e.g., correlations among feeding, antipredator, or mating behavior) (Sih et al. 2004a). Guppies (Poecilia reticulata) provide a great model system to study behavior. Guppies are small, freshwater tropical fish that inhabit still pools in swift-flowing streams, and the backwaters of small rivers in mountain forest areas of Trinidad (Houde 1997; Magurran 2005). In this study I attempted to answer the following questions using three low predation populations of guppies : 1) Do guppies display a behavioral syndrome for aggression and/or courtship across light situations?; 2) Are there mean level changes in aggression or courtship across light situations?; 3) Are mean level changes influenced by differing social environments that include or lack sexually receptive females?; 4) Are there correlations between behavior and the androgen hormones testosterone and 11-ketotestosterone?; 5) Are there correlations between behavior and the stress hormone cortisol?; 6) Are there mean level changes in hormone release rates across light environments?; and 7) Is flexibility in hormone release rates influenced by social environments that include or lack sexually receptive females? Guppies exhibit behavioral syndromes for both aggression and courtship. Furthermore, guppies exhibit behavioral flexibility for both aggression and courtship, but only in social environments that include sexually receptive females. I found no correlations between behavior and androgen hormones. I also did not find any correlations between behavior and the stress hormone cortisol. Furthermore, I did not find any mean level changes in hormone release rates across light environments. Interestingly, cortisol levels were higher in social environments in which sexually receptive females were absent. Many studies have looked at how the environment influences courtship behavior in guppies, especially employing high predation populations, but few studies have examined aggressive behavior or behavior in general with low predation populations. Furthermore, few studies have determined the role social environments play, and how hormones may interact with behavior. This study is important because it helps illuminate how low predation populations deal with changes in light intensity environments, and adds to what we understand about guppy behavior in general.