incubation interval and located if hatching does not occur in a 

 reasonable time. Factors affecting hatching may be divided into 

 biotic and abiotic. Biotic factors include: poaching, 

 predation, destruction by other turtles, damage by invading root 

 systems, fungal infection, and disturbance associated with a 

 variety of human activities from sand compaction to sand mixing. 

 Abiotic factors include: sand accumulation, inundation by rain 

 or salt water, or erosion. 



Monitoring hatching success can identify the type and extent 

 of management required on a nesting beach. These surveys are 

 also important in evaluating the effectiveness of management 

 practices which are currently being used. It should be 

 remembered that when one source of nest mortality is eliminated 

 through beach management, the effect of another factor of nest 

 mortality increases. For example, if 90% of the nests are being 

 depredated by a predator (including man) , the removal of the 

 predator or the protection of the nests will not result in a 90% 

 increase in hatching. Other factors such as tidal (salt water) 

 flooding of nests will affect a greater number of nests. This 

 increase in the effects of alternate sources of nest mortality, 

 when one source is controlled, is due to the fact that nests are 

 vulnerable for a longer period of time. Because of this 

 compensatory effect, it is advisable to evaluate beach management 

 practices by continuing to monitor hatching success. 



A quantification of hatching success is an important 

 indicator of the status of a sea turtle population. While 

 hatching success is usually calculated during the operation of a 

 hatchery, there is very little quantitative information on 

 hatching success on unmanaged beaches where man is neither a 

 positive nor a negative factor. Thus, we don't know the level of 

 hatching success required to maintain a stable population, 

 although hatching success >50% would appear to be normal on most 

 natural beaches. 



Annual hatchling recruitment is also an important statistic 

 in the development of useful, predictive models. Hatchling 

 recruitment may be determined for an individual island or, more 

 importantly, should be estimated for an entire region or 

 population. These models are, or at least may become, important 

 in predicting population trends or in developing management 

 plans. The development of reliable predictive models is 

 particularly important for long-lived species such as sea turtles 

 with characteristic deferred maturity. 



Aerial Surveys of Tracks 



The principal use of aerial beach surveys has been to locate 

 previously unknown nesting beaches or to survey remote or 



223 



