Transcript: “The zip and bass sounds were only produced by a competing male against a mating pair or when there was male competition for a receptive (recently moulted) female (Fig. 8). Specifically, competing male crabs would alternate between producing zip trains and bass trains when exposed to a receptive female. The bass train followed after a zip train 82% of the time. In five out of the seven mating trials, males engaged in fights with other male crabs in the tank, and in two of these trials, females were also injured.”

Source: Sound production and associated behaviours in the New Zealand paddle crab Ovalipes catharus