Mate‐ and Oviposition‐Influenced Host Preferences in the Coral‐Feeding Snail Cyphoma Gibbosum

Mate—searching has been hypothesized to influence the host preferences of small grazers, yet no previous field data have examined this idea. I examined the host preferences of Cyphoma gibbosum, a generalist gastropod that feeds on gorgonian corals, and tested if mate searching or oviposition preferences contributed to variation in host preferences. I constructed experimental reefs containing three species of gorgonian corals at uniform densities and placed snails on these reefs either alone or in group of four. Half of the groups of snails were single—sexed while the other half contained two snails of each sex. I observed snail movements by conducting daily censuses of three reefs and constructed transition matrices describing the movements of snails in each treatment among the three species of coral. Snails showed preferences for some hosts over others, and these preferences varied due to both mate searching and oviposition. Snails preferred to occupy Briareum asbestinum over Plexaurella dichotoma or Pseudopterogorgia acerosa, but these preferences were strongly influenced by previous experience. Moreover, females tended to move from B. asbestinum to Plexaurella dichotoma to oviposit, and back to B. asbestinum afterwards. Finally, both males and females moved frequently towards members of the opposite sex, in order to copulate, which influence their distribution among hosts. These data reveal that behaviors associated with mating can influence host preferences and need to be considered in understanding host utilization patterns.