Choosy Gulf pipefish males ignore age but prefer active females with deeply keeled bodies (choose by body depth and display); ornamentation has no effect

Choosy Gulf pipefish males ignore age but prefer active females with deeply keeled bodies. Andrew P. Anderson, Adam G. Jones. Animal Behaviour, Volume 155, September 2019, Pages 37-44. https://doi.org/10.1016/j.anbehav.2019.05.018

Highlights

• We investigated factors influencing male choice in S. scovelli.
• Males chose females based on body depth and display rather than ornamentation.
• Female ornamentation was correlated with female body size, fecundity and courtship.
• Female age did not affect mate choice, female fecundity, ornamentation or courtship.
• Faster growth in females had no impact on any of the tested traits.

Abstract: Within Syngnathidae (pipefish, seadragons and seahorses), male pregnancy often results in choosy males and competitive females. Females in these species often evolve secondary sexual traits and engage in courtship displays that make their ornaments more noticeable to males. Most syngnathids probably continue to grow larger throughout their lives, but we know little about the relationship between age and mating competition in these taxa. Here, we use the Gulf pipefish, Syngnathus scovelli, to investigate the roles of ornament size, courtship activity level, age and fecundity in female mating competition. We conducted male choice trials that allowed males to choose between similarly sized females of different ages. We also measured age and size at maturity. We found that females with larger ornaments were deeper bodied and engaged in longer courtship displays, yet males chose females based on body depth and display rather than ornamentation. This result suggests that ornamentation serves to help males assess female quality. Female age plays no role in male choice or in female ornamentation. Our finding that males care more about female phenotype than female age considerably simplifies the interpretation of mating patterns in natural populations of Gulf pipefish, which are characterized by considerable age structure.
Keywords: agemate choicesex-role reversalsyngnathid