An endocrine disrupter increases growth and risky behavior in threespined stickleback (Gasterosteus aculeatus).

There is considerable concern that endocrine disrupting chemicals (EDCs) can affect wildlife and humans. While several studies have reported that acute exposure to EDCs can cause changes in reproductive traits, we are in the early stages of discerning whether such changes have significant deleterious fitness consequences. In this study, chronic exposure of threespined stickleback (Gasterosteus aculeatus) to an environmentally relevant level of an EDC used in the birth control pill and post-menopausal hormone replacement therapy produced changes in growth and behavior that were related to fitness. Exposure to 100 ng/l ethinyl estradiol accelerated growth rate and increased levels of behavior that makes individuals more susceptible to predation (activity and foraging under predation risk). Moreover, the costs of exposure to ethinyl estradiol took their ultimate toll via mortality later in life, and were particularly high for females and for one population. The ecological approach taken in this work revealed heretofore unexamined effects of EDCs and has direct implications for the way we evaluate the impact of EDCs in the environment.