Animal Behavior - Biology 420/543 |
Bowling Green State University, Fall 2008 |
Discussion and Pre-Lab Preparation: see Lab 4
Question: Are males courting females randomly, or do they show preferences for size or coloration? Null hypothesis (Ho): Males court females without regard for morphological characteristics. Alternate hypothesis (Ha): Males court females differentially as a function of female morphology. Experiment: Explore the behavior associated with mate choice and test whether males preferentially court females of larger size or brighter coloration.
Preparation: Social encounters of guppies are staged in observation tanks for groups of three students each. The tank contains gravel and is filled with de-chlorinated water at a depth of 20cm. We need a small aquarium net, and a divider.
Procedures: Place 3 females of different size and coloration into the tank. Add 2 males from a separate holding tank where they had been kept isolated for at least a few hours. Set up an observation schedule for 30 minutes. Remove the divider and observe without disturbing the animals. Note occurrences of courtship for each recipient female (large, medium, small or plain, medium, colorful)
Statistical Analysis: Consider differences in the number of courtship patterns that were received by each female. First tabulate the number of courtships received by females as a function of their respective morphological characteristic. What are the chances to find such differences due to chance alone? Given a certain number of courtship incidences, how many would we expect if morphological characteristics play no role. Contingency tables (Chi-square tests, or G-tests) help you with this decision. They allow you to estimate under a given null hypothesis whether a particular outcome of an experiment should be considered "rare" or "common". We had decided beforehand how rare the outcome would have to be so we would reject the null hypothesis in favor of the alternate hypothesis. To analyze perform a Chi-square test on these data.
Answer questions: Based on these results, formulate your conclusions on whether you think that male guppies prefer females with a certain characteristic over others. If yes, can you hypothesize about the evolutionary significance of such a choice?
Question: Do behavior patterns of courting males occurr in random order? Null hypothesis (Ho): Courtship behaviors occurr in random order. Alternate hypothesis (Ha): Courtship behaviors are temporally structured. Experiment: Explore the behavior associated with mate choice and test whether individual behavior patterns occurr in a temporal association with other behaviors.
Preparation: same as above
Procedures: Place 3 females of different size and coloration into the tank. Add 2 males from a separate holding tank where they had been kept isolated for at least a few hours. Set up an observation schedule for 30 minutes. Remove the divider and record the order of behavior patterns of a single animal.
Statistical Analysis: Evaluate whether the occurrence of a particular behavior is independent of a subsequent one. For this analysis, each cell of the matrix represents a transition from behavior A (rows) to behavior B (columns). Tabulate the frequencies of these transitions. Given a certain number of courtship incidences, how many would we expect if their order is random. Contingency tables (Chi-square tests, or G-tests) help you with this decision. They allow you to estimate under a given null hypothesis whether a particular outcome of an experiment should be considered "rare" or "common". We had decided beforehand how rare the outcome would have to be so we would reject the null hypothesis in favor of the alternate hypothesis. Analyze these data using a temporal analysis.
Answer questions: Based on these results, formulate your conclusions on whether you think that courtship behavior of male guppies occurrs in a particular sequence. If so, then summarize these sequences with a flow chart.