Contests over reproductive resources in female roller beetles: Outcome predictors and sharing as an option

Abstract

Fights among females are frequent, although less attention has been placed on them than on male fights. They arise when females compete for food, oviposition, mates, brooding sites, or access to resources which increase offspring survival. It has been shown that the outcome of female fights may be less predictable by asymmetries in resource holding power, than in male fights. Male roller beetles fight over food resources, food balls, needed for mating and nesting, and it has been show in some species that asymmetries in reproductive experience and resource holding power in terms of size predict fight outcome, including ties in which contenders cut and split the food ball. In this study, we tested the influence of asymmetries in reproductive status (experience) and body size on female fight outcome in the carrion roller beetle Canthon cyanellus cyanellus. As predicted, and as previously found for males of the same species, female reproductive status of both contenders and relative size predict fight outcome. Larger and reproductively experienced contenders have a higher probability of winning. Furthermore, ties are more likely in fights involving opposing asymmetries (vgr. Large reproductively naïve owner versus small reproductively experienced intruder). Also as predicted, food ball splitting is more likely to be started by the predicted loser. This mode of resource sharing may be the result of a fighting strategy in which the costs of continuing to fight are greater than the benefits of not splitting, if a fraction of the disputed resource is more than the minimum needed for the present reproductive needs, and reduces costs associated to a longer fight.

Contest dynamics for food and reproductive resources are defined by health condition in a dung beetle

“…Males of C. cyanellus with higher body dry mass and larger body size were more successful in contests for food. Our results corroborate previous studies performed with C. cyanellus reared under laboratory conditions, which showed that larger males have higher probabilities to win contests for females (Chamorro‐Florescano et al, , ). In addition, heavier males showed a significantly shorter latency to start ball‐rolling with females.…”

“…As this study was conducted in the field, a larger sample size could not be obtained; therefore, it is important to interpret the results with caution, as some significant effects may not be detected with low sample sizes due to low statistical power. However, the number of samples was similar to other studies behavioral studies conducted with C. cyanellus in controlled conditions, which presented strong, statistically significant effects (Chamorro‐Florescano & Favila, ; Chamorro‐Florescano et al, , ). This confirms that the behavioral responses measured in our study are strong enough to be detected despite the low statistical power resulting from the low sample size.…”

“…Parameters related to health status, as the indicators of body condition and immune defense analyzed in this study, may be determinant when an individual recognizes a food or reproductive resource and invests energy to fight for it. Canthon cyanellus is a species in which males contest fiercely for food resources and mates (Chamorro‐Florescano, Favila, & Macías‐Ordóñez, , ). Health condition is seemingly a key parameter in the regulation of contests and their outcome (Briffa & Sneddon, ).…”

“…This study shows that body condition and PO activity affect the contest dynamics for food and mating in ball‐roller dung beetles. Body size is the parameter most frequently used to analyze effects on resource contests in dung beetles (Chamorro‐Florescano et al, , ; Heinrich & Bartholomew, ; Sato & Hiramatsu, ). Here, we show that body dry mass, which, unlike body size, is not fixed at the emergence of the adult insect, also affects the outcome of contests.…”

Consequences of pharmacophagous uptake from plants and conspecifics in a sawfly elucidated using chemical and molecular techniques

“…RHP is commonly determined by the size of an individual and its weapons or factors linked to its condition, such as persistence capacity or strength (for review see Vieira and Peixoto, 2013). For example, larger competitors can be more likely to win an interaction against smaller or less experienced individuals (Chamorro-Florescano et al, 2011). However, RV can influence contest occurrence and outcome (Stockermans and Hardy, 2013); for example, females with offspring are more likely to win contests against males over burrows than females without offspring (Figler et al, 1995).…”