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Figure 1. Areas monitored for olive ridley nesting in Sergipe, Brazil.

The coastline of Sergipe is composed of high energy beaches with an open, rock-free offshore approach. Beaches are backed by coastal sand dunes and in some areas lagoons are located relatively close to the dunes; several major rivers discharge on this coastline. Nesting takes place during the Brazilian summer from September to March; loggerheads (Caretta caretta), hawksbills (Eretmochelys imbricata) and green turtles, (Chelonia mydas) also nest on these beaches, but almost 90% of the nests are laid by olive ridleys. TAMAR maintains three stations in Sergipe at Ponta dos Mangues, covering 36 km, Pirambu, covering 53 km, and Abais, covering 36 km (Figure 1). The most intensely monitored area of the 135 km total is in Pirambu. Night patrols, conducted at low tide or during falling tide between 1 October 2004 and 15 March 2005, covered only the northern 26 km, with most effort concentrated on 12 km of beach and extended to the remaining 14 km if tidal conditions permitted. Females encountered were measured for curved carapace length (CCL) from the middle of the nuchal notch to the posterior tip of the supracaudals and tagged with inconel tags on the front flippers. Females were weighed with a Filizola digital balance, which had a maximum capacity of 500 kg. The beach was marked by stakes at every kilometer and the location of the nest noted.

Of the 226 ridleys encountered during the night patrols, the renesting interval of 18 olive ridleys was noted. The renesting interval was between 19 and 40 days (Table 1). In the literature, the renesting interval for ridleys lies between 14 to 75 days and appears to be governed by environmental factors (Plotkin et al. 1997; Pritchard 1969; Schulz 1975). Using 14 days as the minimum renesting interval in olive ridleys, some of the intervals recorded i.e. 27, 29, and 40 days (Table 1), may potentially include one or more missed nesting events. The mean distance between consecutive nests of these females was estimated to be 5 km (SD = 2.7, range = 1-11 km, n = 18). The mean weight of these females after egg deposition, the first time they were encountered, was 41.3 kg (SD = 4.7, range = 33.8-56 kg, n = 18; Table 1). On the subsequent nesting encounter their mean weight was 39.5 kg (SD = 3.9, range = 33.8-52 kg, n = 18; Table 1). These values are higher than mean female weights recorded in Suriname after nesting (mean = 35.7 kg, n = 14; Pritchard 1969) and greater than or similar to female weights from Mexico (mean = 39.25 kg, n = 136) depending on whether mean weight from the first or second encounter is compared, but lower than weights recorded for females in India (mean = 49.5 kg, n = 108; Marquez 1990). Nesting females had lost body weight on their subsequent nesting event (n = 16) aparte from two females who indicated no weight loss; mean weight loss was 1.8 kg (SD = 1.1, range = 0-4 kg, n = 18; Table 1) and may reflect reduced feeding at the nesting beach.

Table 1. Weights of olive ridleys after nesting, weight loss between nesting events, renesting interval, and curved carapace measurements.

Although most of the nesting has been found to take place at night, on some days turtles were found to nest in the afternoon, as early as 1550 hours. Observations indicate that early nesting occurred on very windy days. It is hypothesized that this may be a strategy to prevent predation of the shallow olive ridley nests because all evidence of nesting on the sand surface was estimated to disappear within 15 to 20 minutes; the crab-eating fox (Cerdocyon thous) is the main nest predator in this region. In Mexico, sand blowing in the wind has been suggested to deter predators from accessing the beach (J. Seminoff, pers.comm.). However, this requires quantitative evaluation as several other factors may contribute to early nesting. Nevertheless, it is interesting to note that ridley arribadas in Rancho Nuevo, Mexico, and Eilanti, Suriname, have also been observed to take place during periods of strong wind, and were even delayed until the wind had picked up (J. Seminoff pers. comm.; Pritchard in press; Schulz 1975). No correlation between wind speed or temperature and arribada timing was found by Cornelius (1991) in Costa Rica.

With the loss of arribadas in Suriname, monitoring of this increasing olive ridley population in Brazil will provide important information on olive ridleys in the Atlantic. The major threat to this population is from shrimp trawlers in these waters because coastal Sergipe is an important shrimping area (da Silva pers. comm.). An adult female with fully developed eggs that stranded on the beach during the nesting season was found to have shrimps in its esophagus suggesting a potential overlap in feeding and fishing areas (Castilhos pers. comm.). Therefore, the continued survival of this population depends in part on mitigating olive ridley bycatch in these waters.

Acknowledgements: We would like to thank the fishermen, local agents and Pirambu’s communities for their collaboration with the conservation program. Special thanks to Pirambu´s Station Biologist (Marilda I. Weber) and the trainees/university students (Fabio Picinato and Lelia Matos) who helped to collect the data. Projeto TAMAR, a conservation program of the Brazilian Ministry of the Environment, is affiliated with IBAMA (the Brazilian Institute for the Environment and Renewable Natural Resources), is co-managed by Fundação Pró-TAMAR and officially sponsored by Petrobras. Our thanks to M. Godfrey, J. Seminoff, and L. Soares e Soares who commented on earlier drafts.

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