The Greater Blue-Ringed Octopus found in Australian waters cannot figure out the sex of its partner until a specially modified arm has checked out the target

Males were equally likely to copulate with other males as females,

Most male-to-male copulations ended rapidly in amicable separation, while in male-female copulations the male was less enthusiastic about departing and would take more than an hour and a half, to ensure fertilization, the scientists said.