Hawksbill turtle

Eretmochelys imbricata is a sea turtle of the family Cheloniidae that Linnaeus described in 1766 under the name Testudo imbricata ^[1]. In Peru it is called «tortuga carey» ^[2]. It is the most tropical of the sea turtles recorded in the country ^[3], and most of its Peruvian records come from Tumbes and Piura ^[3]. On the IUCN Red List it is listed as Critically Endangered ^[4].

Compared with the green turtle, which shares its habitats in northern Peru, the hawksbill is recognised by several traits taken together: carapace scutes that overlap like roof tiles, a serrated carapace margin, an elongated snout, two claws on each front flipper, four prefrontal and three postorbital scales, and no ridge along the middle of the lower jaw ^[5]. Hawksbills caught at El Ñuro have been seen with a density of epibionts on the plastron that is rare among the green turtles there ^[5].

In January 2014 a juvenile turtle of 47.3 cm curved carapace length with traits of both species was caught at El Ñuro, Piura; its mitochondrial DNA and morphology showed that it was the offspring of a female hawksbill and a male green turtle, and it was the first sea turtle hybrid documented in the Southeast Pacific ^[5]. Because it looked overall like a green turtle, the authors warn that other hybrids may go unnoticed without a careful examination ^[5].

Similar species

• Chelonia mydas: The green turtle has carapace scutes that sit edge to edge without overlapping, a smooth carapace margin, a snout that is not elongated, a single claw on each front flipper, two prefrontal and four postorbital scales ^[5].

It lives in tropical and, to a lesser degree, subtropical waters of the Atlantic, Indian and Pacific oceans; in the eastern Pacific it is found mainly between Mexico and Ecuador, although in warm El Niño years it has reached 14° S, off Pisco ^[6]. In Peru it has been reported from the Los Manglares de Tumbes National Sanctuary south to Pisco, in Ica ^[7].

Peruvian records include sightings at sea, catches in fishing gear, strandings and shells kept as ornaments or for sale; most come from Tumbes and Piura, and its presence in the south appears tied to El Niño or to warm currents ^[3]. Even so, IMARPE identified live hawksbills at La Aguada, one in 2016 and two in 2017, which is unusual because the site lies further south than its known range ^[3].

In the eastern Pacific it is found on algal beds, rocky reefs and, above all, mangroves ^[5]. In Tumbes there is a resident population in the international channel of the mangroves, on the border with Ecuador ^[6]. In the Virrilá estuary, in Piura, four stranded shells were found between 2013 and 2016, and the species was recorded up to 17 km inland, in the upper estuary ^[3].

It does not nest in Peru ^[5]. The nine eastern Pacific sites with more than 10 nests in any season are in Mexico, El Salvador, Nicaragua, Costa Rica and Ecuador, and 80.6 % of the nests documented up to March 2016 were concentrated in three mangrove estuaries in El Salvador and Nicaragua ^[8].

On eastern Pacific beaches, nesting females average 84.6 cm curved carapace length, lay about 159.1 eggs per nest and about 2.0 clutches per season, 20.1 days apart, and come back to nest every 2.2 years on average ^[8]. Nesting peaks in January and February in South America, and in June and July in Central America ^[8]. It is thought to need 17 years or more to mature ^[8].

The hawksbills that reach Peru are almost all juveniles: of all those reported in the country, only one was not ^[5]. Eleven animals caught incidentally in the north averaged 38.9 cm curved carapace length, between 28.3 and 49 cm, and the largest recorded on the Peruvian coast, at 79.0 cm, stranded in Tumbes in October 2008 ^[3]. Around Pisco, 7 animals gave a mean size of 45.2 cm ^[6].

It feeds mainly on sponges and corals ^[7]. In coastal areas the adult diet also takes in other cnidarians, snails, polychaete worms, bryozoans, crustaceans, sea urchins, fishes, algae and seagrasses ^[6]. Peru's 2019 national plan notes that no information on its diet had been recorded in the country ^[3].

Females followed by satellite after nesting made short trips, of 283.1 km at most, or stayed nearby, and 15 of 18 settled in mangrove estuaries to feed ^[8].

Between 2014 and 2017, satellite transmitters were fitted to 8 juveniles in Sechura Bay, measuring 34.7 to 47.5 cm curved carapace length, with tracks lasting between 9 and 489 days: 6 never left the bay and 2 left and covered more than 1000 km, going past the Galápagos Islands ^[9]. The authors regard the bay as a feeding area where juveniles stay for long periods ^[9].

Its global category is Critically Endangered ^[4]. In Peru it is also classed as Critically Endangered, and the norm that lists it bans hunting, capturing, keeping, trading, transporting or exporting it for commercial purposes ^[10].

At the nesting sites studied across the eastern Pacific only 528 nesting females had been documented between 1983 and March 2016, and the authors estimate that, adding those not yet tagged, there would be fewer than 700 ^[8]. Before the conservation programmes people ate almost 100 % of the eggs, except in Ecuador; today the concerns are the conversion of mangroves into shrimp farming ponds and tides that flood the nests, such as those that swamped more than 30 nests in Jiquilisco Bay in August 2015 ^[8].

Off Lambayeque, between 1996 and 1998, gillnets caught a single hawksbill among 383 turtles, in January 1998, at the most intense point of El Niño, 800 m from the shore ^[11]. In Tumbes none was caught in 190 observed gillnet sets between 2017 and 2019; the authors find this striking and note that there the species is associated with shallow mangrove areas ^[12]. In Sechura Bay, the routes of the tagged juveniles that stayed matched the grounds of the bottom set net fishery by 33 % on average, and small-scale fishing and pollution are among the threats they face there ^[9].

Peru's National Plan for the Conservation of Sea Turtles covers the period 2019-2029 and deals with the five sea turtle species found in the country, the hawksbill among them ^[3].

Not medical advice. For a sting, a poisoning or an allergy, seek medical care.

Any species of sea turtle can turn out to be toxic as food ^[13]. In October 2010, on Murilo Atoll in Chuuk (Federated States of Micronesia), after the meat of one hawksbill turtle was eaten, 6 people died, 4 of them children, and another 95 fell ill; 84 % of those who ate it fell ill, and the risk rose with the amount eaten ^[13]. The laboratory did not identify the causative agent, and the outbreak was attributed to chelonitoxism, poisoning from eating sea turtle ^[13].

The illegal trade in its shell for handicrafts is one of its threats: in Latin America alone, 29 countries supplied shells from 460 220 turtles, and the exports of Panama and Cuba alone were equivalent to 152 070 and 106 948 turtles ^[6].

In 2010, 13 shells were counted in fishers' homes and restaurants in San Andrés, Pisco ^[3]. In Tumbes, according to a study cited by IMARPE researchers, traders or craftspeople from Piura or Chiclayo ask for hawksbill shells and pay up to 80 soles for each one ^[12].

The hawksbill is one of the frequent turtles in the Mar Tropical de Grau National Reserve, and the 2026 master plan points to critical habitats for it in the Arrecifes de Punta Sal sector ^[2]. In Tumbes it has been seen inside the Los Manglares de Tumbes National Sanctuary, mainly in the international channel on the border with Ecuador ^[12]. Between 2014 and 2017, 6 of the 8 juveniles tagged in Sechura Bay spent their whole tracking period there ^[9]. At El Ñuro it is scarce: in 11 in-water surveys between 2010 and 2014, 186 different green turtles were caught and only 2 hawksbills were seen ^[5].