Biological Sciences, School of


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Cowles, S.A. 2013. Trade-offs in Male Lek Behavior. M.S. Thesis: University of Nebraska-Lincoln.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Biological Sciences, Under the Supervision of Professor Robert M. Gibson. Lincoln, Nebraska: December, 2013

Copyright (c) 2013 Sarah A. Cowles


In lek mating systems, males aggregate together and perform courtship displays to visiting females. However, display may be energetically expensive and reduce the time available for foraging. These costs in turn could lower energy reserves, which could decrease survival. I examined trade-offs in male lek behavior using two methods: 1) I conducted an empirical study of how sharp-tailed grouse (Tympanuchus phasianellus) males allocate time between courtship display (“dancing”), agonism, foraging, and inactivity in relation to female numbers both within and across days. I also measured head turning rates during these same behaviors as a proxy for visual attentiveness to the surroundings. 2) I created a stochastic-dynamic programming (SDP) model to investigate how the trade-off between reproductive success and survival (mediated by body condition) affects male reproductive strategies. In my empirical study, I found that the proportion of males engaged in display increased significantly with female numbers whereas foraging decreased significantly with female numbers both within and across days. This indicates that males increase display at the expense of reduced foraging time at periods of high female attendance. In addition, during display, males turned their head only half as frequently as during other activities, which suggests reduced visual attentiveness during display and the potential for increased predation risk. In the SDP model, initial body condition largely determines the optimal seasonal breeding strategy. Males with initially lower body condition are predicted to forage early in the season, maintain lower condition throughout the season, and delay the onset of maximum display effort compared to males with initially higher condition. The results of the two studies suggest that male lek behavior is constrained by both the costs of display and the survival cost of maintaining body condition.

Adviser: Robert M. Gibson

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