been attempted. Some information on food preference is available from 

 fishery catch statistics and the food habits of a few species are known 

 from studies of gut contents (e.g., the lemon shark - Banner, 1972; Clark 

 and von Schmidt!, 1965; Randall, 1967). 



Obviously, feeding is essential behavior for sharks and in the case 

 of interactions with man - perhaps their major activity. Thus, although 

 studies of natural feeding are difficult to accomplish, programs of 

 research incorporating innovative techniques for the field deserve high 

 priority. Some attacks on man may well be motivated by social factors, 

 as noted above but undoubtedly feeding motivates others. Certainly^ the 

 danger from shark attack is acute during certain types of group feeding, 

 such as those culminating in the "feeding frenzy." 



e. Responses of Sharks to Specific Stimuli 



Numerous studies have been conducted on the responsiveness of sharks, 

 both captive and free-ranging, to specific stimulus situations, often 

 somewhat artificial in nature due to a desire to control certain con- 

 founding variables. The aim of such studies has often been to determine 

 not only the gross stimuli "perceived" by the subjects, but to provide 

 insight into more specific factors which are associated with a given 

 sensory modality, such as sensitivity, masking, adaptation, activation of 

 response by selective factors, etc. It is hoped that future efforts along 

 such lines will continue to contribute to a better understanding of how 

 free-ranging sharks detect and locate objects of interest within their 

 sphere of influence. 



When interest is directed at determining the range and sensitivity of 

 sensory modalities, programs often incorporate conditioning paradigms 

 (behavioral or physiological) or electrophysiological techniques. These 

 subjects will be covered in a later portion of this report. 



1) Acoustic Stimuli 



It had long been suspected by fishermen and divers that many sharks 

 were highly responsive to water-borne sounds (Eibl-Eibesf eldt and Haas, 

 1959; Hobson, 1963; Wright, 1948). That suspicion has now been elevated 

 to conclusive fact, our knowledge being greatly augmented since the initial 

 demonstration of shark attraction by low frequency sounds (Nelson and 

 Gruber, 1963). The phenomenon of acoustic attraction appears widespread 

 among the active, predatory species; to date, such attraction has been 

 experimentally shown by members of at least 20 species, covering five 

 families (Banner, 1968, 1972; Limbaugh, 1963; Myrberg, 1969, 1972b; 

 Myrberg et al. , 1969a & b, 1972; Nelson and Johnson, 1970, 1972; Nelson 

 e_t al . , 1969; Richard, 1968). In general, the most effective sounds for 

 attracting sharks are low frequency (800 Hz or below - with attractiveness 

 apparently increasing with decreasing frequency to, at least, 10 Hz) and of 

 a pulsed nature, i.e., apparently simulating hydrodynamic or other sounds 

 produced by wounded (struggling) or actively feeding, or otherwise milling, 

 fishes. These conditions are believed to represent feeding opportunities 

 for large predacious fishes - sharks included. Erratic or intermittant 

 pulsed presentations appear more effective than those having pulses of a 

 constant repetition rate. Yet, within the latter group, the more rapid 

 the rate, the more attractive the sound, at least up to 20 pulses/sec. 



