Sex ratio modulates reproductive output and dung burying behavior in dung beetle <em>Gymnopleurus sturmi</em> (Macleay, 1821) (Coleoptera: Scarabaeidae)

<p>Dung beetles are important ecosystem engineers as they play an important role in recycling dejections from animals. Dung beetles have evolved different behaviours, including dung ball rolling for their egg and developing offspring. Ball rolling is a complex behaviour that varies between species.  In some species, males roll the dung ball and females choose partners based on this, while in other species, males and females work together to form the ball. Competition can be fierce, and fighting and ball stealing are common. <em>Gymnopleurus sturmi</em> is a ball rolling species that exhibit gregarious behaviours.  In this study, assess sex-related roles in ball rolling as well and the impact of varying sex ratios on the number of balls produced either left at the surface, or buried and fertilized (pear-shaped), and emergence rates of the offspring. Results show that both males and females are capable of producing dung balls, and higher numbers were obtained when males and females were separated. Female-biased sex-ratio produced mostly buried and fertilized balls, while male-biased sex -ratio produced more unburied balls left on surface.  When females were alone, they produced the maximum number of total dung balls compared to the rest of the treatment. On the other hand, emergence rate was found to be higher when more males were present When females were alone, emergence rate was extremely low, suggesting a lack or a scarce sperm storage. In a gregarious species like <em>G. sturmi,</em> finding a partner would be easier than for other dung beetle species, which could explain an increasing competition between males and reducing the need to store sperm on the longer term. This study highlights the diversity of behaviours present in this important type of animal.   </p>