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In the Eastern Pacific (EP), the olive ridley is the most abundant sea turtle species and ranges from US to central Chile; however, it is most commonly observed in waters off Mexico and Central America (Eguchi et al. 2007; Olson et al. 2001a, 2001b). Currently, arribada beaches occur in Panama, Costa Rica, Nicaragua and Mexico (Abreu-Grobois & Plotkin 2007; NMFS & USFWS 1998). Non-arribada (i.e. solitary) beaches are located mainly in Mexico but nesting is reported from Mexico to Colombia and rarely from Ecuador and Peru (Hays-Brown & Brown 1982; NMFS & USFWS 1998). All the females that nest in the different rookeries in the EP are believed to belong to the same subpopulation (Abreu-Grobois & Plotkin 2007); however, it seems that some demographic independence does exist among beaches (Abreu-Grobois & Plotkin 2007; Lopez-Castro & Rocha-Olivares 2005).

Figure 1. Locations of recorded nests (circles) and sites where interviewees observed nesting activity (stars) in the northern Peruvian Coast. Nest references at Punta Malpelo and Nueva Esperanza from Hays-Brown & Brown 1982 and Vera et al. 2008, respectively.

Diet analysis, feeding observations and turtle migrations have shown that coastal Peru (nearshore and offshore) is a significant foraging area for sea turtles (Hays-Brown & Brown 1982; Paredes 1969; Shillinger et al. 2008) but is not considered an important area for nesting, although nesting does occur in Peru. Hays-Brown & Brown (1982) reported an olive ridley nest laid in 1979 in Punta Malpelo, Tumbes (Fig. 1) with 79 undeveloped eggs and 1 egg with an embryo. Turtle crawls were also observed in beaches south to Punta Malpelo, suggesting nesting activity. In the subsequent two decades, no other evidence of nesting has been reported. However, in recent years, nesting activity has been observed.

New findings: In July 2000, a nest in Caleta Grau, Tumbes (Fig. 1) was observed by fishermen who informed personnel from the Tumbes Laboratory of the Instituto del Mar del Peru (IMARPE) and from Fondo de Desarrollo Pesquero (FONDEPES). When the nest emerged in September, the hatchlings were raised in captivity in the facilities of the FONDEPES Aquaculture Center La Tuna Carranza at Puerto Pizarro, Tumbes (Perez et al. 2001). Nine months later, in June 2001, we were able to evaluate the olive ridley surviving hatchlings. The mean hatchling length was 18.7 ± 1.5 SD cm (range: 15-22.1, n=35) for curved carapace length from notch to tip (CCL) while their mean weight was 988 ± 229 SD g. (range: 630-1530, n=35). Turtles weighing more than 1.1 kg (n=9) were tagged with inconel tags in both rear flippers and all turtles were released 1 hour offshore.

During 2001 and 2002, we conducted a sea turtle survey along the Peruvian coast (3080 km), covering a total of 57 localities, including ports, fishing villages, beaches, and guano islands and guano points. In 47 of these sites, we informally questioned a total of 85 inhabitants, particularly fishermen, to learn about sea turtles in the area. Our questions covered a wide range of subjects including the presence of different sea turtle species and habitats, abundance, food items, human interactions, exploitation, commercialization, uses, strandings, and nesting activity. We specifically asked if they knew how sea turtles reproduce and if they have seen reproductive events. Of the 47 sites where we conducted interviews, we obtained information about nesting activity, including direct observations of nesting females, eggs and/or hatchlings in only five locations: Punta Capones, El Bendito, Playa Hermosa and Caleta Grau in Tumbes, and Negritos in Piura (Fig. 1). All these areas are located in the two northernmost coastal departments of Peru.

Five years elapsed until we obtained new evidence of sea turtles nesting in Peru. In August 2007, several open nest chambers and one nest were observed by a house guard on a beach north of El Ñuro, Piura (Fig. 1). The nest was located about 50 m from the high tide mark and the guard estimated it had around 300 eggs, but eggs were not counted. Subsequently, within a week, the guard and a local fisherman removed all the eggs to eat them, either cooked or raw as accompaniments while drinking pisco (Peruvian liquor distilled from grapes).

Figure 2. Three eggs observed in a beach north of El Ñuro, Piura.

Three eggs, were observed, photographed and measured by F. A. (Fig. 2), who was also allowed to keep one for genetic analysis. This egg was analyzed using molecular techniques to determine the sea turtle species. A 740 base-pairs fragment of the control region of the mitochondrial DNA was amplified and sequenced using primers LTEi9 and H950 (Abreu-Grobois et al. 2006), and subsequently compared with available sequences for Pacific sea turtles on Genbank (<http://www.ncbi.nlm.nih.gov/>) and SWFSC Marine Turtle Research Program <http://swfsc.noaa.gov>. Results confirmed that the sea turtle clutch from El Ñuro was deposited by an olive ridley sea turtle with haplotype O. This haplotype has been previously reported for East Pacific nesting populations, including Costa Rica and Mexico (Bowen et al. 1998; Briseño-Dueñas 1998; Lopez-Castro & Rocha-Olivares 2005), and represents the first genetic information from a sea turtle nesting in Peru.

The eggs had a mean diameter of 3.68 cm (range: 3.65-3.70, n=3), which is smaller than the global average (3.93 cm) reported for this species (Miller 1997), slightly larger than the range reported for Playa El Valle (2.9-3.6, mean = 3.3 cm), an important nesting beach in Colombia (Barrientos & Ramirez 2008) but is within the size range of olive ridley eggs in EP rookeries (Hirth 1980). This olive ridley nest is the southernmost record of a sea turtle nest in the Eastern Pacific.

More recently, in March 2008, another nest was observed in Nueva Esperanza, Tumbes (Fig. 1), when 36 hatchlings were observed during hatchling emergence and positively identified as olive ridleys (Vera et al. 2008).

Olive ridleys can be found along the entire Peruvian coast, but they are more common in the north where sea surface temperatures are warmer (Hays-Brown & Brown 1982). They are the third most abundant species captured on pelagic longlines in Peru (Kelez et al. 2008) and the second most commonly captured species in gillnets in the Pisco area (de Paz et al. 2002). Biometric data from our longline on-board observer project and from field surveys show that the mean CCL of olive ridleys in Peru is 61.1 ± 7.4 SD cm (range 42-78, n=63, unpublished data). Using the average size of nesting females as the best estimate for minimum adult size (Miller 1997) and data from the closest significant nesting beach Playa El Valle in Colombia (Barrientos & Ramirez 2008), 33% of the individuals observed in Peru can be considered adults. However, if we removed the turtles caught by longlines and consider only the individuals found during coastal surveys (strandings and carapaces on sale), which seem to come from more near shore areas, the proportion of adults changes to 57% (average CCL = 64 ± 7.2 SD cm, range 48.3-78, n=28). Also, during longline on-board observations we were able to observe 3 adult males showing secondary sexual characteristics and one of them measured 63 cm CCL. These findings indicate that olive ridleys are a common species in Peru and that there is a large adult component in coastal waters. This is not restricted to years with incursions of warm water (el Niño or ENSO), but is generally the case.

The recent observations of nests in Peru are not unique in the Southeast Pacific. In the last five years, nesting activity has been also reported in Ecuador. Alava et al. (2007) reported a nest with 50 eggs and one dead late-stage embryo in a beach near Manta in October 2004. The authors also reported a hatchling found in October 2006 in a beach in the Province of Esmeralda. More recently, increasing evidence of nesting activities was found in several beaches in continental Ecuador: Ayampe – Puerto Rico, Montañita, Puerto López, Jupiter, Portete and Isla de la Plata (Baquero et al. 2008).

In Pacific Colombia, the olive ridley is the most common nesting species. The Colombian Institute of Coastal and Marine Research (INVEMAR) considers four beaches to have abundant olive ridley nesting (more than 100 turtles/beach/year). These are in order of importance Playa El Valle, Amarales, Mulatos and Vigia (Ceballos-Fonseca et al. 2003). In addition to these four, an additional 36 other beaches are used by olive ridleys for nesting. Despite being abundant in Colombia, the nesting aggregations there are threatened by intensive direct capture of nesting females and egg predation for human consumption (Barrientos & Ramirez 2008; Ceballos-Fonseca et al. 2003). Nonetheless, current conservation efforts might be increasing the survival of hatchlings. Some hatcheries are protecting a large number of nests, especially at Playa El Valle, which has had an active hatchery since 1991 (Ceballos-Fonseca et al. 2003).

Nesting at low density in higher latitudes, such as the recent nesting events in Peru and Ecuador, may reflect relaxed natal homing in olive ridleys, which facilitates the colonization of beaches distant from the respective natal beaches. Studies have shown that olive ridleys do not always return to the same beach to nest. A small proportion of ridleys have been found using both Nancite and Ostional beaches; other adult females from Nancite and Ostional have been observed nesting, or about to nest, in Chacocente, Nicaragua and Escobilla in Mexico (Cornelius & Robinson-Clark 1986). More recently, a female that nested in Osa Peninsula, Costa Rica was seen nesting in Playa El Valle, Colombia, 728 Km away (Barrientos & Ramirez 2008). The relaxed natal homing behavior may explain the lack of strong genetic structure observed among EP olive ridley rookeries (Bowen & Karl 2007). Wandering gravid females are important to the species’ continuity in the long term, as particular nesting beaches may become unsuitable over time for reproduction. In northern Peru, coastal inhabitants often assert that sea turtle nesting was common “in the past,” probably around the 1960s (Hays-Brown & Brown 1982). Therefore, the new nesting activity might be a re-colonization of beaches at the southern limit of their reproductive distribution in the Eastern Pacific.

The recent nesting activity reported in Peru and Ecuador might also be the result of a combination of two factors: increased research efforts and more conservation. Even though there are no ‘baseline’ data, there has been greater activity related to sea turtles in Peru and Ecuador in the past 10 years. Additionally, in the EP, actions such as protection of nesting females and nests and by-catch mitigation in coastal an oceanic waters have also increased, and likely have had a positive impact on olive ridleys. If population numbers in the area are increasing, nesting events could be increasing as well. The hatcheries established in Playa El Valle, the most important nesting beach in Pacific South America, have been protecting nests and releasing hatchlings into the population since 1991. Considering that time to maturity has been calculated in 13 years for olive ridleys (Zug et al. 2006), an increase in the adult population since 2004, with concomitant increased nesting activity, seems like a plausible possibility. Additionally, nesters numbers in the 2 most important arribada beaches in the EP, Ostional and Escobilla, increased considerable from the 1980s to the year 2000 (Chaloupka et al. 2004).

However, the intense capture of olive ridleys in the EP must not be forgotten. During the 1960s and 1970s, olive ridleys were harvested for the leather industry. Slaughter houses dedicated exclusively to this sea turtle species operated intensely in Mexico and Ecuador in the 1970s until populations began to decline (Cliffton et al. 1982; Cornelius 1982). As a consequence, many arribada beaches collapsed and have not been able to recover to past levels yet (Abreu-Grobois & Plotkin 2007). Currently, olive ridleys are legally protected in all countries of the EP with some exceptions for egg harvest in Panama, Costa Rica, Nicaragua and Guatemala (e.g. Hope 2002); El Salvador banned this practice in February, 2009 <http://www.mag.gob.sv>. Nevertheless, in spite of the legal protection, enforcement is sub-optimal and two principal threats remain in the region: fisheries bycatch and egg exploitation (Cornelius et al. 2007; Frazier et al. 2007).

The findings presented here are an encouraging sign of conservation efforts and monitoring. The need for increasing conservation programs in the northernmost coastal departments of Peru (Tumbes and Piura) is evident. Under these circumstances, it is extremely important to protect each nest deposited on Peruvian beaches and increase conservation efforts. Nests in northern Peru will not only add to population numbers but also have the potential of contributing to a higher proportion of males due to colder temperatures compared to rookeries north of Peru (Fiedler & Lavin 2006). We recommend the implementation of regular monitoring of beaches and the protection of each natural nest.

Acknowledgments: We thank O. Perez and A. Lujan for giving us access to the headstarted hatchlings and for all their efforts to release them offshore, Dr. Llanos for all his help in Tumbes, APECO for their support, NMFS-SEFSC for field materials and M. Godfrey for his valuable comments. The sequencing and genotyping facility of the University of Puerto Rico-Rio Piedras is supported in part by the following agencies: NCRR-AABRE grant no. P20RR16470, NIH-SCORE grant no. S06 GM08102, University of Puerto-Rico Biology Department, NSF-CREST grant no. 0206200 and NINDS-SNRP USA NS39405. The information reported were obtained under the following research permits: 016-2002-INRENA-J-DGFFS-DCB, 049-2002-INRENA-DGFFS-DCB, 014-2004-INRENA-IFFS-DCB, 017-2004-INRENA-IFFS-DCB, and 117-2008-INRENA-IFFS-DCB.

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