recent study has indicated that some attacks are motivated by social 

 factors rather than feeding (Baldridge and Williams, 1969). Understanding 

 the causal factors which underlie behavior will require experimental 

 manipulation and comparative behavioral analysis among a variety of 

 representative species. An important aid in this regard will be to obtain 

 and standardize dossiers of behavior patterns (i.e., ethograms) such as 

 those initiated by Myrberg and Gruber (1974) for the bonnethead shark and 

 by Johnson and Nelson (1973) for the gray reef shark. These will not only 

 provide the opportunity for comparative analysis, but they will also be 

 vital in planning, analyzing and interpreting future observations from 

 both the field and laboratory. 



c. Rhythmic Behavior 



The universality of rhythms in biological systems is now established, 

 and recent studies indicate that sharks are not exceptions (Hobson, 1968; 

 Myrberg and Gruber, 1974; Nelson and Johnson, 1970; Randall, 1967; 

 Springer, 1963; Graeber, 1974). For example, diel rhythms, regulated by 

 the daily light cycle, are known to determine the activities of tropical 

 reef fishes (Hobson, 1965, 1968, 1972; Collette and Talbot, 1972). Thetr 

 influence on the behavior of sharks, however, is less well known. Quanti- 

 tative information exists on only a few species (horn, swell, angel and 

 blue sharks), all of which are basically nocturnal (Nelson and Johnson, 

 1970; Standora e_t a_l. , 1972). We are not aware of any information on 

 rhythms related to moon phase and only little that is related to tidal 

 cycles. Seasonal or other long term rhythms are only slightly better 

 known. For example, migrations have been studied by various tagging pro- 

 grams (Davies and Joubert, 1967; Kato and Carvallo, 1967; Olsen, 1953, 1954; 

 Springer, 1960; Tester, 1969), but they still remain pootly understood. 

 Since long-term tagging programs generally yield low return for the effort 

 expended, we recommend their support only where a well established fishery 

 permits adequate recovery. 



Controlled studies, demonstrating endogeneity, have been conducted 

 for only two species - certain circadian rhythms of the horn and swell 

 sharks (Nelson and Johnson, 1970). The effects of exogenous factors on 

 rhythms, other than those involving the daily light cycle, are virtually 

 unknown . 



The most profitable line for future research would seem to center 

 around the daily routines of sharks under natural or semi-natural conditions. 

 Recent advances in ultrasonic telemetry and direct observations offer much 

 promise in this area (Herrnkind, 1974; Myrberg, 1973; Standora et al. , 

 1972). Knowledge of daily movements, levels of responsiveness and habitat 

 preference will aid in predicting and perhaps controlling those activities 

 of sharks that conflict with the interests of man. 



d. Feeding Behavior 



We know of only one significant experimental study of feeding behavior 

 in free-ranging sharks (Gray reef, blacktip reef and reef whitetip sharks - 

 Hobson, 1963); yet, since the experimental design demanded that food be 

 presented to the sharks, natural feeding was not involved. There are 

 scattered, anecdotal accounts of natural feeding (e.g., Bullis, 1961; 

 Eibl - Eibesfeldt and Haas, 1959), but quantitative observations have not 



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