Berry, Frederick 



Aerial and Ground Surveys of Derroochelys coriacea 

 Nesting in Caribbean Costa Rica. 1987 



6450 SW 81 street 

 Miami, Florida, 3 3143 USA 



Aerial beach surveys along the Caribbean coast of Costa Rica 

 during the period March-June of 1983-1986 had recorded a 

 significant number of nests of Dermochelys coriacea spread along 

 the entire coast and concentrated in the northern portion. They 

 had also recorded, along with a few visits to the beaches, 

 relatively heavy destruction of nests by mammals, primarily Homo 

 sapiens . 



During 1987, a two phase survey was made. Four aerial beach 

 surveys were flown over most of the coast near the middle of 

 March, April, May and June. Two ground truth surveys were made 

 almost daily, at two five-mile beach sections, south of Boca de 

 Matina (March 5-June 30) and north of Laguna Jalova (April 1-June 

 15) . The original survey records are archived in the WATS II 

 Reports/Data Set series. 



The great majority of the tracks and nests recorded were by 

 Dermochelys coriacea . Records of Eretmochelys imbricata and 

 Chelonia mydas are preserved in the original data records. 



Because the tracks of leatherbacks (also greens and 

 hawksbills) are often short or short-lived, and the nest body- 

 pits are more durable, the aerial counts concentrated on body- 

 pits for nesting estimates (after distinguishing 1987 leatherback 

 body-pits from those of greens laid late in 1986) . 



Ground survey records were made the morning after nightly 

 nesting in one-half mile sections over the five-mile subzone. 

 They recorded fresh events: false crawls, and tracks with nests 

 as either dug-up or not dug. The old marks recorded tracks 

 separately and nests (as body-pits) as either dug-up or 

 obviously/apparently not dug. 



GROUND SURVEYS 

 Matina Subzone: The daily surveys (3/1-7/4) recorded 865 

 nests (Fig. 1) , and 886 nests were estimated for the season (2/4- 

 8/29) . The majority of nesting was between 4/11-6/6 (75%) . The 

 peaks of nesting were from 5/16-6/6. The most fresh nests 

 recorded in one day was 2 3 (5/23) . False crawls were rare in 

 March and July, accounted for 24.4% of the fresh tracks during 

 April-June, with an estimated 280 false crawls for the season 

 (Subzone 9A) . 



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