Exposure to an agricultural contaminant, 17β-trenbolone, impairs female mate choice in a freshwater fish

• We investigated the impact of 17β-trenbolone on sexual selection in the guppy.
• Unexposed female guppies spent significantly more time associating with unexposed males than trenbolone-exposed males.
• Trenbolone-exposed females showed no preference for either exposed or unexposed males and associated with males less overall.
• Trenbolone exposure had no impact on male morphology or behavior.

Despite the pivotal role sexual selection plays in population dynamics and broader evolutionary processes, the impact of chemical pollution on female mate choice is poorly understood. One group of chemical contaminants with the potential to disrupt the mechanisms of female mate choice is endocrine disrupting chemicals (EDCs); a broad class of environmental pollutants that can interfere with the endocrinology of organisms at extremely low concentrations. Recent research has revealed that estrogenic EDCs can affect female mate choice in fish, but the impact of androgenic EDC exposure is yet to be studied. To address this, we investigated the effects of an environmentally relevant concentration of trenbolone – an androgenic steroid used as a growth promoter in the cattle industry – on female mate choice in wild-caught guppies (Poecilia reticulata). We exposed male and female guppies to 17β-trenbolone for 21 days (measured concentration 4 ng/L) via a flow-through system, and found that trenbolone-exposed female guppies spent less time associating with males, and were less choosy, compared to unexposed females. In contrast, trenbolone had no impact on male reproductive behavior or morphology. This is the first study to show that androgenic EDC exposure can disrupt female mate choice, highlighting the need for studies to investigate the behavioral impacts of environmental contaminants on both sexes.