Abstract

Sea lampreys (Petromyzon marinus), an invasive pest in the Upper Great Lakes, avoid odours that represent danger in their habitat. These odours include damage-released alarm cues from conspecifics and predator cues, like 2-phenylethylamine hydrochloride (PEA HCl), a promising predator cue found in the urine of mammalian predators. The objectives of this experimental study were: (1) determine if the avoidance response of sea lamprey to PEA HCl is graded or hypersensitive, (2) determine if the avoidance response to the combination of a predator cue (PEA HCl) and damage-released alarm cue is synergistic or additive. To meet the first objective, groups of ten sea lampreys were placed in an artificial stream channel and presented with stepwise concentrations of PEA HCl ranging from 5E-8 to 5E-10 M and a deionized water control. Sea lampreys exhibited graded avoidance behaviour in response to PEA HCl. To meet the second objective, sea lampreys were exposed to PEA HCl, conspecific damage-released alarm cue, and a combination of the two. Sea lamprey responded to the combination of predator cue and damage-released alarm cue in an additive manner, as the response to the combination of cues did not trigger a significantly greater response than the sum of their separate effects.