It takes two to tango: female movement facilitates male mate location in wild northern watersnakes (Nerodia sipedon)

To facilitate location of mating partners, females of many taxa emit chemical signals (i.e., sex pheromones) to inform male conspecifics of their location and reproductive status. Males subsequently alter their movements to increase their likelihood of encountering females and this movement has been historically viewed as a primary determinant of mate location. However, because of the method of female sex pheromone release, particularly via terrestrial trails, female movement likely contributes to mate location; however, information on this topic is lacking. We monitored the movements of 27 free-ranging radio-equipped adult female northern watersnakes (Nerodia sipedon) during the 2007-2009 mating seasons to determine if females employed movement tactics to facilitate location by males. For a limited period following shedding, female movement increased. During this period, they were approximately five times more likely to be located by a male than during the remainder of the mating period. Further, females experienced maximum male mate location following shedding. Because increased movement is associated with increased costs, females may minimise these costs by restricting this risky behavior to a limited period of time when their attractiveness and/or receptiveness is presumed to peak.