Nest location and pheromone concentrations interact to influence female nest choice in sea lamprey

Animal communication is dynamic; factors such as signal attributes, signaller and receiver positioning, and environment can interactively influence information exchange. However, most research has focused on the signals and preferences while neglecting the broader context in which they function. Using sea lamprey, Petromyzon marinus, we studied the effects of male signalling location on female nest choice. Male sea lamprey aggregate on spawning grounds in rivers where they build nests and release a sex pheromone to attract females. In controlled studies, females select nests with the highest relative concentration of pheromone, indicating some degree of mate choice following pheromone concentrations. In reality, however, the characteristics of pheromone signals detected by females (e.g. concentration) are shaped not only by the odour males emit but how they are transmitted downstream via river currents. We hypothesized that the effects of pheromone preferences on female nest choice also depend on the location of male nests. To test our hypothesis, we first surveyed the spatial distribution and use frequency of spawning nests in a wild population of sea lamprey. We then conducted instream behavioural assays using paired nest sites at two experimental locations and found that nest location and pheromone concentration impacted female nest choice. These behavioural results, along with indirect evidence for differences in pheromone plume dispersal at each site, suggest that signalling location and pheromone concentration may influence mate choice in sea lamprey. Although additional environmental factors likely influence natural mating decisions, our results highlight the importance of considering both signal attributes and the surrounding environment when studying communication networks.