Preferential incorporation of dark, coloured materials into nests by a mound‐nesting stream cyprinid

Abstract

We compared size and colour characteristics of rocks used by male cutlip minnows Exoglossum maxillingua to build nests to those of streambed background materials. We found that materials used to construct conspicuous, mound-shaped nests were uniform in size and darker and more colour-saturated than background materials of the same size. To our knowledge, this phenomenon is the first reported example of fish selecting nest materials based on colour and has important implications for the conservation of mound-nesting stream cyprinid species.

How sexual and natural selection interact and shape the evolution of nests and nesting behaviour in fishes

“…Stone carrying and dropping are crucial parts of the male's effort to attract females and when a male drops stones into the nest, females have been described to rush into the nest for spawning [ 92 ]. Finally, in cutlip minnows, Exoglossum maxillingua , males carefully select the stones to be darker and more colour-saturated than the background when building their mounds [ 93 ], similar to sticklebacks that use algae of contrasting colour to mark the nest opening (§3b). It seems likely that choice of stone colour makes males more attractive to females, but as far as we know, this has not yet been investigated.…”