# Sex Ratio Modulates Reproductive Output and Dung Burying Behavior in Dung Beetle Gymnopleurus sturmi (Macleay, 1821) (Coleoptera: Scarabaeidae)

## TL;DR

This study explores how sex ratios affect dung ball production and offspring success in the dung beetle Gymnopleurus sturmi, finding that females produce more balls alone while males boost offspring emergence rates.

## Contribution

The study reveals sex-specific roles and the impact of sex ratios on reproductive behaviors and offspring success in the gregarious dung beetle Gymnopleurus sturmi.

## Key findings

- Females produce the maximum number of dung balls when alone.
- Male presence increases offspring emergence rates.
- Female-biased sex ratios result in more buried and fertilized dung balls.

## Abstract

Dung beetles are important ecosystem engineers as they play an important role in recycling faces from animals. Dung beetles have evolved different behaviors, including dung ball rolling for their egg and developing offspring. Ball rolling is a complex behavior 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 with fighting, and ball stealing is common. Gymnopleurus sturmi is a ball rolling species that exhibits gregarious behavior with adults congregating on a dung source. This study assesses sex‐related roles in ball rolling as well as the impact of varying sex ratios on the number of balls produced, either left at the surface or buried and fertilized, and emergence rates of the offspring. The theoretical number of offspring per female was used as a measure of fitness. Results show that both males and females can produce 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 the surface. When females were alone, they produced the maximum number of total dung balls compared to the rest of the treatments. 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 reduced sperm storage. Using the theoretical number of offspring per female, no difference in fitness was observed when males and females were both present. In a gregarious species like G. sturmi, 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 for the longer term. This study highlights the diversity of behaviors present in this species.

This study examines the sex‐specific roles and the impact of sex ratios on dung ball production and offspring emergence in the dung beetle species Gymnopleurus sturmi. It finds that both males and females can produce dung balls, with females producing the most when alone, while male presence increases offspring emergence rates. The research suggests that in this gregarious species, easy access to mates may lead to increased male competition and reduced need for long‐term sperm storage in females.