SECT. 4] SOUND PRODUCTION BY MARINE ANIMALS 559 



spine is moved rai)idly back and forth by males as they display before the 

 female (Clark, 1950). This is presumptive evidence that sound is a part of 

 the sexual behavior of these species, since sound production by dorsal spine 

 stridulation is known in the related filefish genus Monocanihus (Burkenroad, 

 1931). 



The most exhaustive studies in this connection are those by the animal 

 behaviorist Tavolga (1956, 1958, 1958a) of the goby, Bathygohius soporator, and 

 the blenny, Chasmodes hosquianus. In Bathygohius the establishment of territory 

 and the courtship of the female by the male proceeds by a complex set of visual, 

 chemical, and auditory stimuli, of which low grunts emitted by the male are an 

 essential part. These grunts appear to be stimulated by the release into the 

 water of an ovarian fluid by the female and in turn stimulate generalized 

 activity on the part of the female which is oriented by visual stimuli received 

 from the male. Other males may also be attracted to the scene of sound- 

 production. A similar function for similar sounds was determined in Chasmodes. 



In the cetaceans certain sounds undoubtedly have a sexual significance. 

 Captive Tursiops make peculiar high-pitched yelping sounds during the 

 mating season. These are heard when a female which is being actively courted 

 deserts her partner, but cease when she returns to him. Her return may be a 

 positive reaction to the sounds (Wood, 1954; Tavolga and Essapian, 1957). 



Sexual motives have not yet been attributed to the sound production of 

 strictly marine crustaceans, so far as we are aware, but in the littoral Uca 

 pugilator, a fiddler crab, low-frequency drumming is associated with a sort of 

 dance, called "beckoning", to which the male is incited by the appearance of 

 the female (Burkenroad, 1947). 



B. The Defensive and Offensive Functions 



Although many marine animals, notably cetaceans, seem habitually to be- 

 come silent when hunted or molested, many others produce sounds when they 

 are caught, roughly handled, or otherwise disturbed. And largely on the basis 

 of this behavior, it is supposed that some sounds are of defensive use to the 

 individual. Sound production may accompany other acts which seem to be 

 more clearly defensive in nature. Thus in the burrfish, Chilomycterus spinosus, 

 and in the swellfish, Sphoeroides nephelus, a "whining scrape" is made by 

 grinding the incisors together during or after inflation (Burkenroad, 1931). In 

 sculpins of the genus Myoxocephalus and in the flying gurnard, Dactylopterus 

 volitans, drumming noises are made as the flsh spreads its spiny gill-covers 

 (Sorensen, 1884; Nichols and Breder, 1927). In the sea-robin {Prionotus sp.) a 

 low grunt accompanies the erection of the spiny fins (Moulton, 1956) and 

 similar observations have been made for the toad-fish, Opsanus tau (Hildebrand 

 and Schroeder, 1928). In the langouste, Panulirus argus, sound-production 

 accompanies the violent abdominal contractions of the restrained animal, 

 which bring. into play the various spines and sharp edges of the exoskeleton 

 (Moulton, 1957). 



