Pietro Pollo, Shinichi Nakagawa , Michael M. Kasumovic

Male mate choice occurs in several animal species, but we know little about the factors that influence the expression of this behaviour. Males vary in their capacity to acquire mates (i.e. male quality), which could be crucial to male mate choice expression but it is often overlooked. Using a meta-analytical approach, we explore inter-individual variation in the expression of male mate choice by comparing the mating investment of males of different qualities and phenotypes to high- and low-quality females. We used two datasets that together contained information from 60 empirical studies, comprising 52 species. We found that males of all qualities and phenotypes prefer high-quality females, but differ in the strength of such preference. High- and medium-quality males are choosier than low-quality males. Similarly, males that are larger or in greater body condition are choosier than their counterparts. In contrast, male body mass and age are not associated with changes in male mate choice. We also show that experimental design may influence our understanding of male mating investment patterns, which may limit the generalization of our findings. Nonetheless, we argue that male quality may be an important feature in the expression of male mate choice.