Where and what is the habitat of sea turtles in Mexico?

The Mexican Official Standard seeks to preserve the several species of marine turtles found in Mexico, many of which are on the verge of extinction.

Where and what is the habitat of sea turtles in Mexico?
Sea turtles: Every year the Olive Ridley turtle arrives at Mazunte Beach in Oaxaca. Image by StockSnap from Pixabay

Sea turtles are widespread around the world, but they have retained their position as an endangered species for some time. As a result, the species that swim in Mexican seas are already covered by the Mexican Official Standard (NOM059), which has been in effect since 2010.

Here we discuss when turtles are in season, their habitat, and what they consume. According to the Ministry of Environment and Natural Resources (Semarnat), there are six different species scattered throughout national waters.

Where are sea turtles found in Mexico?

The Green/Black Sea Turtle is the first of the six species that can be found in Mexican waters (Chelonia Mydas). One of the rare aquatic herbivores that primarily consume algae and seagrasses is this species of sea turtle.

The black sea turtle is located in Michoacan, whereas the green sea turtle is found on beaches around the Gulf of Mexico and the Caribbean, including Tamaulipas, Veracruz, Campeche, Yucatan, and Quintana Roo.

Another species of sea turtle that is most in danger of going extinct is the Kemp's ridley (Lepydochelys kempii), which spends 90% of its time nesting on the beach in Rancho Nuevo, Tamaulipas, before migrating to the Gulf of Mexico and the southeast of the United States.

The Olive Ridley sea turtle (Lepidochelys olivacea), which is currently the most prevalent sea turtle, may be spotted all along the Mexican Pacific coast, but its primary nesting grounds are in Oaxaca.

Another species is the loggerhead turtle (Caretta caretta), which differs from the other species in that it may be found in both the deepest and shallowest parts of the ocean. Although they spend the majority of their early years in open ocean currents, this turtle once had a significant presence in the area surrounding the Baja California peninsula.

The hawksbill turtle (Eretmochelys imbricata), which may be found in tropical seas of the Atlantic, Pacific, and Indian Oceans, is one of the most endangered turtles in the world.

Last but not least, the Leatherback Turtle (Dermochelys coriacea) is the least well-known species among them all despite being the most oceanic. It can grow to a length of 1.78 meters and weigh up to 500 kilograms, making it the largest marine reptile. The Pacific Ocean is home to the leatherback turtle, with Michoacán, Guerrero, and Oaxaca having larger densities.

Garbage and sargassum cause the death of sea turtles in Cozumel

The death of turtle hatchlings due to the sargassum barrier on the beaches is increasing, according to Cozumel's environmental authorities, since dozens of turtle hatchlings have been found dead on San Martin beach, on the eastern side of the island, apparently unable to pass through the mounds of algae, in addition to their natural predator such as birds.

The turtle camp "Punta Sur", first authorized in Cozumel, comprises eight kilometers of coast and to date, the CEA has detected 650 turtle nests; but the problem is that on the coastline people are not aware of not throwing garbage and the sargasso prevents the turtles to come out naturally, that is why the hand of man must intervene to remove those that remain at the bottom.

Only 1% of turtles reach adulthood

Turtle nesting begins in March, at the end of April, and beginning of May the turtles begin their journey over the beaches to make their nests in the sandy part. The white turtle species comes very close to the dune, moving up to 40 meters away from the beach, where the vegetation is; the other species, the loggerhead turtle nests in the middle of the beach, and nesting can take from 45 minutes to two hours.

The turtles weigh from 200 to 250 kilograms, while the green turtle and the loggerhead are the largest, which can measure up to one meter and 20 centimeters in carapace alone; loggerheads lay from 80 to 100 eggs, green turtles lay from 100 to 120 or even more. Incubation time depends on the species, but can be from 50 to 70 days, depending on temperature.

When visitors see a turtle on the beach, do not disturb them because after the ovation the animal is tired and the only thing it needs to do is to go to the sea to take shelter and look for food. Regarding the natural predators of turtles, in the case of adult turtles, they are the big sharks, but in the case of Cozumel, there is rarely predation of adult turtles.

The species most threatened by predators is the loggerhead because it is almost flush with the beach. The survival rate can be one in 100 and there are seasons when it is one in a thousand, it all depends on the natural conditions since the grouper and the mahi-mahi are predators of turtle hatchlings.

Current status of sea turtles in Mexico

Of the eight species of sea turtles known in the world, seven inhabit Mexican beaches and two of them, the Kemp's ridley (Lepidochelys kempi) and the black turtle (Chelonia agassizii), occur exclusively on these beaches. The Kikila turtle ( Natator depressus ) is the only one that does not nest in Mexico and its distribution is restricted to the coasts of Australia. In Mexico, several sandy beaches along the Pacific, Gulf of Mexico, and the Caribbean Sea offer ideal nesting sites for females, with optimal humidity and temperature conditions for this phase of their development.

For the protection and study of turtles, the nesting process is one of the most important periods because it is when the greatest efforts are made to prevent the nests from being plundered and the females from being captured. From June to September, the females leave the sea to go to the same beaches where they were born to deposit their eggs in nests dug in the sand. After this process the females return to the sea, so the clutches lack parental care.

The incubation period ranges from 45 to 60 days and, in each clutch (which depending on the species can be from 2 to 8 per season) they deposit between 60 to 100 eggs. During their development and on the journey from the nest to the sea, the hatchlings are easy prey for predators such as seagulls, crabs, dogs, and raccoons that feed on them. In their juvenile stage, at the age of 2 or 3 years, they move towards lagoons, estuaries, and bays where they find optimal conditions for growth. The natural mortality rate of sea turtles is high during the first stages of life, so it is considered that out of every one hundred hatchlings, only one or two reach adulthood.

However, the reduction of sea turtle populations throughout their global distribution is mainly due to anthropogenic factors with a long history. Apart from the excessive direct fishing that was practiced until recent times, other factors include the plundering of nests, the incidental capture of juveniles and adults in shrimp nets, the alteration or destruction of their nesting habitats, and poorly planned urban and tourist development and the increasing pollution of the seas. As a result, some sea turtle populations have virtually disappeared. This situation has led to the declaration of all sea turtle species as threatened or endangered.

It is estimated that only one out of every one hundred sea turtle hatchlings reaches adulthood. This situation has led to the declaration of sea turtles as threatened or endangered.

In Mexico, it was in the early 1960s when sea turtle capture intensified, as their skin replaced that of the crocodile, the shell and meat were industrially processed, and large quantities of eggs were collected and sold in markets in Mexico City, Guadalajara, Mazatlán, Oaxaca and Acapulco. In 1972, the then Secretary of Commerce declared a ban on sea turtle capture, and a year later the purchase and sale of eggs were prohibited.

In 1986, 16 beaches were decreed as Reserve Zones and Refuge Sites for the nesting, reproduction, and development of sea turtle species: Isla Contoy, in Quintana Roo; Rancho Nuevo, in Tamaulipas; Ría Lagartos, in Yucatán; Ceuta and Verde Camacho, in Sinaloa; Mismaloya, Teopa and Cuitzmala, in Jalisco; Colóla, Mexiquillo, and Maruata, in Michoacán; Piedra de Tlacoyunque and Tierra Colorada, in Guerrero; Escobilla and Chacahua, in Oaxaca; and Puerto Arista, in Chiapas.

In June 1990, a total ban went into effect for an indefinite period to prohibit the capture and commercialization of sea turtles, as well as the products and byproducts derived from them.

Because they are highly migratory species, sea turtles are also a resource that is shared geographically among several countries. The lack of effective regional management plans for these species can sometimes conflict with and even nullify costly conservation efforts. For example, in early 1993, the United States threatened to impose a trade embargo on Mexico's shrimp exports, arguing that there was a high rate of sea turtle bycatch in this fishery. In response to this situation, a series of preliminary evaluations were carried out on the Mexican coasts and as a preventive measure, the official gazette of February 25 of that year established that the use of sea turtle excluder devices (det's) was mandatory in the Mexican Gulf and the Caribbean Sea.

Before the installation of these devices, technicians, fishermen, and trawlers from the Mexican shrimp fleet were trained. However, reports recently published by U.S. non-governmental organizations show that the U.S. fishing sector has not complied with the legal provisions established in the United States for the protection of these chelonians. The U.S. Endangered Species Coalition states that the cause of turtle mortality is related to the failure of the U.S. fishing industry to comply with the legal provisions established in the United States for the protection of these marine turtles.

Sea turtle conservation efforts should be focused on the factors that have the greatest impact on the decline of sea turtle populations in each region. Accordingly, the strategy for more organized and efficient management should promote and consolidate national, regional, and international collaboration agreements to distribute the commitment to conservation equitably.

Sources: CONABIO, the first issue of its bi-monthly bulletin Biodiversitas by Jacinta Ramírez.