A rebuttal to the claim natural beaches confer fitness benefits to nesting marine turtles.

Survival rates of early life stages (eggs/hatchlings) in marine turtle populations critically influence adult recruitment rate and thus population persistence (Mazaris et al. 2005, 2006). Therefore, for conservation and management purposes, it is particularly important to understand how marine turtle hatching success (percentage of eggs that produce hatchlings) may be affected by human disturbance. Coastal development at nesting habitats is a key issue. Recently, in Biology Letters, Pike (2008) has drawn attention to a critical issue; he investigated whether coastal development (permanent development, e.g. houses) negatively influences hatchling production, and concluded that hatching success is significantly lower at developed beaches. In this article, we discuss some of the concerns we have with Pike’s study, focusing on misconceptions about factors that underlie hatching success and the dataset used. We also explore whether Pike’s conclusions have the conservation merits claimed. Our first disagreement with Pike’s study is that it oversimplifies variability in factors that influence hatching success. As mentioned by Pike ‘.variation in hatching success can be caused by many different factors, including nest site location,.temporal effects.[and] geographic variation.’ However, Pike did not account for the influence of any of these important factors on his study sites and only included data on presence or absence of development. According to Pike ‘.not accounting for such factors.should create sufficient variation in the data to lead to acceptance of a null hypothesis (that natural and developed beaches have similar rates of hatching success)’, and no significant pattern should arise. Then, on finding a significant difference between natural beaches and those that had been developed, Pike attributed low hatching success to the presence of development, thereby assuming that hatching success at a developed beach would have been higher prior to the development. However, by doing this, Pike fails to adequately recognize the risk that the effect found may be a consequence of which beaches have become developed, rather than of the development itself. It could well be that the developed beaches used for Pike’s study were peripheral beaches that experienced poor nesting success prior to being developed or had lower hatching success for other