Table 2.— Counts of northern elephant seal pups in the California Channel Islands subpopulation, including Islas Los 

 Coronados (see Figure 1). Unless otherwise noted, counts were obtained from aerial photographs. Also presented are relative 

 contributions by each island ( RC ) expressed as a percentage of the total pup count and average yearly rates of increase in pup 

 production for each island (/r) and for the Channel Islands subpopulation iSr). 



'The 1958 and 1959 census data averaged and treated as a single census year. 



^Actual counts, followed in parentheses by total pup production estimates which were corrected for times when less than maximum pup numbers can be 

 counted. 

 ^Values calculated from actual pup counts, followed in parentheses by values calculated from total pup production estimates. 

 ■•Land based census. 

 =Only estimated value reported (Bonnell et al. text footnote 1). 



the fact that there is apparently little suitable 

 space available for new elephant seal rookeries on 

 Santa Barbara Island and Islas Los Coronados (Le 

 Boeuf et al. 1975; Bonnell et al. footnote 1) suggests 

 that the numbers on those islands have stabilized 

 and that there will be a concommitant decline in 

 their RC values in future years. 



Estimated Average Annual Rate of 

 Increase by Island (Ir) 



The Ir values peaked between 1958 and 1964 on 

 San Miguel Island and between 1964 and 1972 on 

 San Nicolas and Santa Barbara Islands. Data 

 presented suggest that numbers on Islas Los 

 Coronados probably increased most rapidly be- 

 tween 1972 and 1978. This suggestion is supported 

 by results of a more detailed study of those islands 

 which provide data for intermediate years during 

 this period (Le Boeuf et al. 1975). 



Generally for each island, periods of high an- 

 nual increase in population have been followed by 

 periods of decreasing Ir values. Such trends in 

 reduction of growth rate can be expected to con- 

 tinue until such time as each island's elephant seal 

 numbers reach stability, a pattern of population 

 growth characteristic of other large marine and 

 terrestial mammals (Fowler''). The increase from 

 1972 to 1978 on San Miguel Island is not surprising 



for an island where space does not appear to be a 

 limiting factor, and similar increases might yet 

 occur on the other islands where suitable breed- 

 ing space is available. High rates of increase 

 might also occur on new rookeries as northern 

 elephant seals begin to colonize such areas as San 

 Clemente Island and the mainland (Le Boeuf and 

 Panken 1977; Le Boeuf and Mate 1978). But it is 

 highly unlikely that any of the presently colonized 

 California Channel Islands will ever experience 

 growth periods that will exceed the largest Ir val- 

 ues presented in Table 2. 



Estimated Average Annual Rate of 

 Increase in the Subpopulation (Sr) 



The most rapid growth in the Channel Island 

 subpopulation as a whole apparently occurred be- 

 tween 1958 and 1964. During this period, Sr val- 

 ues reached 0.384 then dropped to 0.121 for 1964- 

 72 and 0.153 for 1972-78. The extremely high rate 

 of increase observed from 1958 to 1964 was proba- 



"Fowler, C. W. 1978. Appendix C. Non-linearity in popula- 

 tion dynamics with special reference to large mammals. In C. 

 W. Fowler, W. T. Bunderson, M. B. Cherry, R. J. Ryel, and B. B. 

 Steel. Comparative population dynamics of large mammals: a 

 search of management criteria, p. 174-220. Report to U.S. 

 Marine Mammal Commission, Wash., D.C. (Available Natl. Tech. 

 Inf Serv, Springfield, VA 22161 as PB80-178627.) 



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