Edwards: Allometry of energetics parameters in Stenella attenuata 



435 



changes the value of the term in brackets only 

 from 1.03 to 1.08). This lack of effect occurs de- 

 spite the fact that D max has an intermediate-level 

 relationship with wet weight (Table 4). 



Examining the placement of MSA b and BD„ in 

 the equation for passive heat loss also illustrates 

 that their relative importance is highly dependent 

 on both parameter placement and relationship with 

 wet weight. Passive heat loss can be estimated as 

 (Edwards, 1992, following Brodie, 1975). 



H„ 



(21.18/BDJ * (37.0-Tj * MSAf/10000.0) * 24 



mv g *(czy iooo.O) 



Collecting and assuming constant all terms ex- 

 cept the energetics parameters BD n and MSA h , 



H u = MSAJBDJ * C, 



where C represents the collected terms. 



Once again, changes in the surface area mea- 

 surement (MSA h ) will lead directly to equivalent 

 changes in estimates of HL,„ and the strong rela- 

 tionship between MSA h and wet weight will be 

 readily reflected in the estimates. However, unlike 

 the case for D max , changes in values used for BD a 

 will have a significant (reciprocal) effect on esti- 

 mates of HL U (e.g., increasing blubber depth by 

 30% [i.e., by a factor of 1.30] will decrease the 

 estimate for H u by about 23% [1/1.30 = 0.77]) ow- 

 ing to the difference in the way the parameter is 

 expressed in the equation. In this case, the inter- 

 mediate-level relationship of BD a with wet weight 

 will be reflected in the estimate of energy flux. 



Allometric effects in parameters related to bone 

 provide an example of largely irrelevant, though 

 statistically significant, trends. The bone fraction of 

 body weight is small (about 10%: Fig. 8A), and its 

 energy density low (less than 1/4 the energy den- 

 sity of blubber, 1/3 the energy density of muscle). 

 Given no indication from the energy densities in 

 the small sample studied that spotted dolphins store 

 lipid within the skeleton, even relatively large 

 changes with size will have little effect on whole- 

 animal energy calculations. Even though the frac- 

 tion of body weight due to bone has an intermediate- 

 level relationship with wet weight, decreasing 30% from 

 5-kg to 30-kg dolphins, the decrease in terms of total 

 body weight is only from 10% to 7% (Table 4). 



Thus, the practical importance of any allometric 

 trend depends on other factors in addition to actual 

 strength of the trend with wet weight, but in general 

 for spotted dolphins, these trends are expressed pri- 

 marily during the first two or three years of life 

 (5-30 kg wet weight). Parameter estimates for small 



20 40 60 80 100 



WET WEIGHT (kg) 



Figure 6 



Relationship between characteristic lengths of fins and total 

 wet weight of body in kilograms for 26 specimens of spotted dol- 

 phin [Stenella attenuata) from the eastern tropical Pacific Ocean, 

 both sexes and all ages (sizes) represented. Lines through points 

 are fitted regressions. 



40 60 



WET WEIGHT (kg) 



Figure 7 



Relationship between average blubber depth and total wet 

 weight of body in kilograms for 29 specimens of spotted dolphin 

 (Stenella attenuata) from the eastern tropical Pacific Ocean, both 

 sexes and all ages (sizes) represented. Lines through points are 

 fitted regressions. 



dolphins (less than about 30kg wet weight) should be 

 derived from measurements on animals near the spe- 

 cific size of interest. Estimates for larger animals, with 

 the exception of the surface area measurements, could 

 be estimated reasonably well from any specimens 

 greater than about 30 kg wet weight. 



Population energetics 



The examples presented above pertain to estimates 

 for individual spotted dolphins. Implications of alio- 



