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The northern coast of Bahia is a major sea turtle nesting area in Brazil, hosting approximately 6,000 nests per year laid by loggerhead (Caretta caretta), hawksbill (Eretmochelys imbricata), olive ridley (Lepidochelys olivacea) and green turtles (Chelonia mydas). Conservation activities on nesting beaches in Brazil began in 1982 and continues today, being carried out by Projeto TAMAR (Brazilian National Sea Turtle Conservation Program) (Marcovaldi & Marcovaldi 1999).

Recently, increasing nest numbers have been observed for loggerheads (Marcovaldi & Chaloupka 2007), hawksbills (Marcovaldi et al. 2007) and olive ridleys (Silva et al. 2007) in northern Bahia. Concurrently, tourist activities have also increased in the region, resulting in the development of villages and small cities along the coast, in addition to the construction of large resorts in front of nesting beaches (Lyrio 2003). This coastal development has greatly contributed to the increasing occurrence of artificial light on the beaches. In this study, we describe a simple and efficient method to identify emerged nests with hatchlings disrupted by artificial lighting and locate the source of the disruption, with experimental data obtained from several beaches of northern Bahia.

During the nesting seasons of 2006/2007, 2007/2008 and 2008/2009, we investigated hatchling behavior on four beaches in northern Bahia, Northeast Brazil. Two (Busca Vida or BV and Santa Maria or SM) are located in residential condominiums areas, with households on average about 40 m from nests and occupied during the summer, which is the period for the nesting season. BV also has a tourist resort. The other two beaches (Arembepe or AR and Berta or BE) are located in isolated areas, with no inhabitants or direct light sources reaching the beaches. All beaches were daily patrolled at early morning during the nesting and hatchling emergence season (September to April), according to standard methodology for fieldwork, described in Marcovaldi & Marcovaldi (1999), where all nests were marked (Figure 1A).

Figure 1. (A) Pictures showing the hatchling’s crawls on the sand at the northeast coast of Bahia. RIGHT is the situation when the majority of hatchlings went toward the sea and WRONG when they went on the opposite direction. (B) Schematic representation of the methodology used for the identification of the track directions (1 to 5) of the hatchling’s crawls disoriented due to a light pollution sources for each disrupted nest.

To assess and document the impacts of artificial lights in each of the beaches, we examined hatchling tracks from nests in the early morning after primary nighttime emergence occurred. If the majority of observed hatchling tracks went to the ocean, we score the nest as “right”. If the majority of observed hatchlings tracks did not go in the direction of the ocean, the nest was scored as “wrong” (Figure 1A). When live hatchlings were found near the houses in the early morning, we promptly released them. For the three seasons of our study, we observed that on the uninhabited beaches (AR and BE), as expected, 100% of observed nests were scored as “right” (Table 1). However, on the developed beaches (BV and SM), some nests were scored as being “wrong” (Table 1). Overall, SM had a higher rate of “wrong” nests than BV, likely due to the higher density and closer proximity of houses to the nesting beach in SM.

Table 1. Total number of sea turtle nests (including loggerhead, hawksbill, olive ridley and green) laid on Berta (BE), Arembepe (AR), Santa Maria (SM) and Busca Vida (BV), during the 2006/2007, 2007/2008 and 2008/2009 nesting seasons, together with nests observed with disrupted hatchling sea finding.

To identify the possible artificial lighting sources causing the observed hatchling disruption, we collected data on the average direction(s) that the hatchlings crawled away from the ocean of each nest (Figure 1B). Using this information, on the following evening, biologists visited the beach with the aim of identifying which light sources attracted the hatchlings. Once indentified, we approached these homes or resorts to speak with the owners or managers, to inform of the impacts of their lights on the turtles and provide them with possible actions to eliminate these impacts. Brazil, there is specific legislation prohibiting the impact of artificial lighting on sea turtle nesting beaches (legislation IBAMA Portaria n° 11 of 30th January 1995 and Bahia’s State Law n° 7.034 of 13th February 1997). These laws prohibit the incidence of light on nesting beaches (IBAMA’s federal law applies to specific regions of the Brazilian coast and Bahia state law applies to specific beaches in the state) from any artificial light source in a range of 50 m from the high tide line.

We also georeferenced each nest with disrupted hatchlings, to enable the visualization of satellite images (i.e. available in Google Earth® software). This helped to identify not only the sources of light that caused hatchling disruption of individual nests but also potential hotspots of artificial light affecting many nests (Figure 2); it also produced maps there were valuable in raising awareness of lightning issues in public meetings with the property owners and managers.

Figure 2. Satellite images used for educational purposes showing examples of light pollution affecting sea turtle hatchlings at Santa Maria beach, northeast Brazil. (A) Situation where some nests, each identified as a numbered flag, had hatchlings that crawled toward (arrows) the same small hotel (circled building). (B) A stretch of beach (surrounded by the box) where the light from public street lamps focused direct on nests (flags numbered) on the beach and hatchlings from several nests had crawled toward the street.

Overall, the method of scoring nests as “right” or “wrong” was simple and quick, and thus easily integrated into the routine morning patrols of beach monitors. Once identified, nests with disrupted hatchling behavior could then be investigated in more detail, and possible sources of artificial light identified.

Despite the low frequency of nests with disrupted hatchlings at SM and BV (<8%), it should be inferred that there is little hatchling disruption by artificial lights along the entire Bahia coast. This is because there is a wide variety of patterns of development behind beaches across the state; we recommend that each beach should be evaluated independently for hatchling disruption.

Our initial success with this simple method of identifying artificial lighting problems on our beaches is promising. However, it may have implications under certain conditions. For instance, moon phase can play a role in hatchling disruption from artificial lighting (Salmon & Witherington 1995). Thus, it may be necessary to continually check for disruption of hatchlings from nests across seasons and perhaps across years, to fully identify problem lighting sources. However, our method is simple and quick enough to implement as a routine measurement during morning patrols.

Acknowledgments. We are grateful to TAMAR staff members who helped to collect the data. Our special thanks to Luciano S. Soares for their careful review and for help in translating of the manuscript into English, and to Matthew Godfrey and an anonymous referee for their valuable contributions to the manuscript. Projeto TAMAR, a conservation programme of the Brazilian Ministry of the Environment, is affiliated with the ICMBio (the Brazilian Institute for Biodiversity Conservation – Instituto Chico Mendes), is co-managed by Fundação Pró-Tamar and is officially sponsored by Petrobras.

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