Does the Apparent Risk of Predation Alter the Response to a Habitat Selection Pheromone in Migrating Sea Lamprey?

Habitat selection is a process dictated by the perception and evaluation of risks and opportunities. During the terminal reproductive migration, the sea lamprey Petromyzon marinus is highly dependent on attractant odors (pheromones) to locate spawning habitat and mates. Recent experiments indicate they also detect and avoid the odor of dead conspecifics that putatively contains an alarm cue while searching for suitable spawning habitat. We investigated whether the apparent risk of mortality (the alarm cue) trumps the habitat quality cue (larval odor) in a series of field experiments. Specifically, we tested (1) whether lampreys discern and react to varying levels of the alarm cue in a threat-sensitive manner, and (2) how the animal responds to combinations of the alarm cue and larval odor to learn how individuals perceive and distinguish between routes to spawning locations during their migration. The results will be discussed in light of improving our understanding of lamprey migratory behavior and the extent to which migratory behavior may be manipulated to achieve either control or conservation goals in invasive and protected populations.