No male mate choice for female boldness in a bi-parental West African cichlid, the rainbow krib (Pelvicachromis pulcher)

Abstract

Background: In many species, males have a lower reproductive investment than females and are therefore assumed to increase their fitness with a high number of matings rather than by being choosy. However, in bi-parental species, also males heavily invest into reproduction. Here, reproductive success largely depends on costly parental care; with style and amount of parental effort in several cases being associated with personality differences (i.e., consistent between-individual differences in behaviour). Nonetheless, very little is known about the effect of personality differences on (male) mate choice in bi-parental species.

Methods: In the present study, we tested male mate choice for the level and consistency of female boldness in the rainbow krib, Pelviachromis pulcher, a bi-parental and territorial West African cichlid. Individual boldness was assumed to indicate parental quality because it affects parental defence behaviour. For all males and females, boldness was assessed twice as the activity under simulated predation risk. Mate choice trials were conducted in two steps. First, we let a male observe two females expressing their boldness. Then, the male could choose between these two females in a standard mate choice test.

Results: We tested for a male preference for behavioural (dis-)similarity vs. a directional preference for boldness but our data support the absence of effects of male and/or female boldness (level and consistency) on male mating preference.

Discussion: Our results suggest female personality differences in boldness may not be selected for via male mate choice.

Keywords: Activity; Assortment; Behavioural consistency; Behavioural level; Behavioural stability; Mating preference; Personality; Predation risk; Sexual selection; Similarity.

Figure 1. Experimental set-up for behavioural tests.

Set-up for (A) the boldness test and for female boldness tests (B) the subsequent mate choice test. Water level for all tanks was 10 cm. Fish are not to scale.

Figure 2. (A) Male and (B) female APR (activity under simulated predation risk) over two boldness tests.

Figure 3. Male preference for the (A) level and (B) consistency of female boldness.

Boldness was measured as APR (activity under simulated predation risk; in cm). Boxplots with 1.5 interquartile ranges, mean (−) and medians (◊); n.s. = non-significant. No deviation from random choice (male strength of preference = 0.50, dashed line) detected.

Figure 4. Male preference for the relative similarity in the (A) level and (B) consistency of female boldness.

Boldness was measured as APR (activity under simulated predation risk; in cm). Relative similarity in average male APR and female APR observed directly before mate choice. Positive values of relative similarity indicate the male’s similarity with the respective bold female of a female dyad was higher than its similarity with the respective shy female. Vice versa: negative values indicate the male was more similar to the shy female than to the bold female. No significant effects detected (n.s., non-significant).