Abstract
The famously diverse body coloration of cichlid fish serves communicative functions in mating and social interactions including competition for resources. Here, we examined the effects of a color pattern trait—the width of a yellow bar on a black body—on territorial competition in males and females of a color variant (“Ikola”) of the Lake Tanganyika cichlid Tropheus. First, measuring integumentary carotenoid concentrations in the yellow and black body regions, we established that wider yellow bars require more carotenoids allocated to body coloration. However, we also detected high carotenoid concentrations in the black body regions (> 100 µg/g fresh skin), raising questions about the function of non-displayed integumentary carotenoids. Behavioral experiments showed that fish with wider bars were quicker to explore an unfamiliar area of the tank. In experiments including presentations of fish dummies, the bar width of ‘territorial’ dummies had no effect on the latency time which test fish took to intrude into the dummies’ territories. However, male test fish performed fewer aggressive acts against wide-barred than against narrow-barred dummy competitors. Our results suggest that intimidation by wide bars as well as correlations between bar width and explorative behavior may contribute to mediating success in territorial Tropheus “Ikola”.
Highlights
Color signals are an important means of communication across the animal kingdom, functioning in various contexts ranging from mate choice and competition to predation avoidance (Maan & Sefc, 2013; Cuthill et al, 2017)
Carotenoid concentrations were measured in the skin and scale samples taken from yellow and black body regions (Table 1)
Because of the low sample size for females (n = 6), we did not test for sexspecific differences in the distribution of carotenoids, but the mean values of carotenoid concentrations in the three body regions show congruent patterns for males and females
Summary
Color signals are an important means of communication across the animal kingdom, functioning in various contexts ranging from mate choice and competition to predation avoidance (Maan & Sefc, 2013; Cuthill et al, 2017). Body coloration can convey information about status and fighting ability and be used to assess opponents and evade unwinnable conflicts, reduce escalation and avoid injury (Rohwer, 1975; Maynard Smith & Harper, 2003; Senar, 2006; Blount & McGraw, 2008). Several studies demonstrated that the hue and the size of colored areas can be correlated with competitive success and dominance (Viera et al, 2008; Jarvistoet al., 2013; Dey et al, 2017; Tinghitella et al, 2018). This was the case in the cichlid fish Tropheus sp. We found a correlation between the outcome of contest competition and the width of the yellow bar, as winners of experimentally staged female–female contests for territories had wider bars
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