The relationship between male sexual signals, cognitive performance, and mating success in stickleback fish

Abstract

Cognitive ability varies dramatically among individuals, yet the manner in which this variation correlates with reproduction has rarely been investigated. Here, we ask (1) do male sexual signals reflect their cognitive ability, and (2) is cognitive ability associated with male mating success? Specifically, we presented threespine sticklebacks (Gasterosteus aculeatus) with a detour-reaching task to assess initial inhibitory control. Fish that performed better were those who solved the detour-reaching task, solved it faster, and required fewer attempts to solve. We then reexamined males' performance on this task over several days to assess learning ability in this context. We next measured sexual signals (coloration, nest area, and courtship vigor) and asked whether they reveal information about these male cognitive abilities. Finally, we examined whether success at attracting a female is associated with male cognition. After controlling for the strong effect of neophobia, we found that no measured sexual signals were associated with initial inhibitory control. Sexual signals were also not associated with change in performance on the detour-reaching task over time (learning). However, females preferred mating with males who had better initial inhibitory control. We speculate that inhibitory control is a critical trait for male sticklebacks. In this system, males perform all parental care, but must avoid eating their own fry which closely resemble their prey items. Therefore, males with better inhibitory control may be more likely to successfully raise their offspring to independence. Our research adds to a growing list of mating systems and taxa in which cognition is important for measures related to fitness.

Keywords: cognition; detour‐reaching task; female choice; inhibitory control; learning; sexual selection; sexual signal; threespine stickleback.

Figure 1

Male threespine sticklebacks and the detour‐reaching task apparatus. (a) Representative males with extensive red coloration (top) and reduced red coloration (bottom). (b) Sticklebacks accessed the food reward (bloodworms on the outside of a clear bag, represented by dark grey lines) by swimming above and into the cut‐out circle on the top of the clear, cylindrical barrier

Figure 2

Male performance on detour‐reaching task over time. Change over time for (a) the proportion of males entering the cylinder, (b) (arcsine square root transformed) entries per attempts, and (c) (log transformed) time to enter the cylinder. Plotted are the mean ± SE

Figure 3

Female choice and cognition. Males who were accepted by females as mates had better inhibitory control. Shown here is the line indicating the marginal effect of inhibitory control, with remaining covariates (throat and eye color, nest area, courtship vigor, body mass, neophobia, and days to build a nest) set to their means. The 95% confidence interval is indicated by the gray shading on either side of the line. This model also included female ID and male ID as random factors. Data points, however, are the means for each male across his trials (usually 2, see 2). The data points are partially transparent; darker regions indicate more overlap between individual points