The tusk is an innervated sensory organ with millions of patent nerve endings connecting seawater stimuli in the external ocean environment with the brain.[20][21][22][23] The rubbing of tusks together which males engage in is now hypothesized to communicate information about the water each has traveled through rather than to represent the previously assumed “male-to-male rivalry“.[22] Narwhals have only occasionally been observed using the tusk for aggressive behavior.