Removal of one source of mortality does not mean that all or 

 even a majority of those eggs will automatically go into the 

 percent hatched rows of balance sheets such as those shown in 

 Tables 1-3 . Stopping poaching on Sand Island also leaves more 

 eggs for raccoons. Eliminating raccoons leave more clutches to 

 be washed away by hurricanes at the end of the season. Saving 

 eggs from tides early in the season again leaves more for 

 predators. The great attraction of artificial hatcheries is that 

 eggs can be saved from a variety of threats. More research on 

 optimal hatchery procedures should be undertaken. 



Example 5; Doomed eggs of leatherbacks 



Various patterns of mortality on different beaches have been 

 mentioned repeatedly. One way to arrive at valid generalizations 

 is to compare the contribution of a particular factor to natural 

 mortality on a number of beaches and try to discern some 

 explanatory principle. This approach has been tried for the 

 doomed eggs of leatherbacks (Mrosovsky 1983a) . It seems 

 remarkable that after long migrations these turtles so often fail 

 to move the few extra meters up the beach necessary so that their 

 eggs are not washed over. Obstructions are not a sufficient 

 explanation. Table 4 compares the frequency of nesting below the 

 high tide lines in a number of different leatherback rookeries. 

 The great variation between beaches is as striking as the high 

 levels for misplaced nests in the Guianas. On the basis of 

 information on beach topography, nesting below the high tide line 

 has been suggested to be more frequent in places where the 

 vegetation on the landward side of the beach is relatively 

 sparse. Without dark masses on the landward side, the danger of 

 hatchlings becoming disoriented and wandering inland increases. 

 The pressures not to lay too far inland result in a proportion of 

 the eggs being laid too near the sea. The behavior of 

 leatherbacks at Culebra, Puerto Rico, fits nicely into this. The 

 females almost always move well clear of the seas on this beach, 

 which is backed by cliffs and hillsides sufficiently large to 

 provide excellent cues for sea finding. 



Nevertheless, some conditions appear to be inconsistent with 

 this formulation. In South Africa, nesting below the high tide 

 line is common, yet the beaches there often lie at the base of 

 tree-covered hills. 



A methodological problem is that the data were mostly 

 derived from predictions about loss of the nest to the seas. 

 These were made on the basis of previous tidelines; actual 

 destruction of these nests was not verified. This introduces 

 imprecision into the study but does not invalidate it altogether. 

 Laying below the high tide line is clearly far more common in the 

 Guianas than in Malaysia (Table 4) . 



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