This mountain river-dweller can be easily found by its cry, an audible honk that is quite unusual on Darwin IV. This sound is the result of air being expelled form its twin bladders during their sudden deflation, a tone which echoes off the cliff sides and can be heard for kilometers. It is believed to be a territorial signal.
Mountain streams on Darwin IV are not rich in plant life and these creatures are forced to spend up to three-quarters of their time searching for their aquatic forage, the red mountain-spike. As a result, bladderhorns are extremely territorial and use their honking as well as their vivid bio-light displays to frighten off challengers.
When confronted by a rival, the bladderhorn will spread its "antlers," pumping up the large bladders in short, angry puffs. This is answered in kind by the challenger, who also begins to circle its rival in a slow and deliberate (as well as comical) tiptoe fashion. This may appear humorous, but it is important to know that the two combatants are in deadly earnest. There is never a fatality result from these territorial displays, but long bloody wounds are very common.