New threat to endangered sea turtles

Three species of turtle can regularly be found around the popular tourist destination of Akumal in the Riviera Maya

Three species of turtle can regularly be found around the popular tourist destination of Akumal in the Riviera Maya

Rising beach temperatures are posing a new threat to endangered sea turtles. A successful conservation project in Mexico is now looking to widen its scope to monitor ambient temperatures in turtle nests.

All sea turtles in the Caribbean are listed by the IUCN (2012) as endangered (green turtle, Chelonia mydas  and loggerhead turtle, Caretta caretta) or critically endangered (hawksbill turtle, Eretmochelys imbricate, and leatherback turtle, Dermochelys coriacea).

The major threat faced by these turtles is loss of nesting habitat in coastal regions. The increasing popularity of the Mexican Riviera Maya as a tourist destination, and beach erosion (man-made and natural) has drastically reduced the number of suitable nesting sites for the turtles in the Yucatan Peninsula. Moreover, light pollution along the coastline from hotels, bars and restaurants has steadily reduced the number of turtles that come in to nest.

Protecting nesting habitats

Sea turtles repeatedly return to the same beach to nest and provide no neonatal care once the eggs have hatched. Consequently, the characteristics of the nest determine whether the eggs will survive or not.

Placement of nests farther inland increases the likelihood of desiccation, and due to the distance the hatchlings have to travel to reach the sea, there is a greater chance that they will be preyed upon. Conversely, nests close to the sea increases the likelihood of egg loss due to erosion or flooding of the nest.

Nest site preferences of sea turtles therefore involve cost-benefit analyses by the females as they attempt to find the most suitable location to lay their eggs, and thus successful sea turtle conservation projects need to ensure that a wide range of potential nesting habitats are protected.

Three species can regularly be found around the popular tourist destination of Akumal in the Riviera Maya. The Hawksbill Turtle can be found feeding around the coral reefs just offshore and the local beaches are important nesting ground for the Loggerhead Turtle and the Green Turtle.

Although Akumal is also a popular tourist destination, the beaches are managed by a local NGO called Centro Ecológico Akumal. Daily patrols locate turtle nests and place protective barriers around them, and night patrols ensure that nesting turtles are not disturbed by tourists. Local residents have agreed to minimise light pollution by closing all shops, bars and restaurants before 11pm and local fishermen and tour boats abide by ‘no go’ areas in which areas of sea grasses are roped off so that feeding turtles will not be disturbed by boats.

The turtle monitoring team at CEA have also monitored the characteristics and success rates of nest sites in order to gather data on the range of habitats used by the turtles and ensure that they remain protected.

As a result of these efforts, the number of turtle nests and hatchlings are starting to increase over time, making the Akumal turtle project one of the few success stories in turtle conservation (see Figure below).

graph

Climate change threats

However, the sea turtles appear to be facing a new threat in the form of changing beach temperatures caused by climate change. The sex of sea turtle hatchlings is determined by the temperature inside the nest. Embryos develop into males when the temperature is approximately 28°C (82°F), whereas the female embryo develops at approximately 31°C (88°F).

Turtle hatchling

Turtle hatchling

If the temperature inside the nest is between these values, then both male and female turtles are created. If temperatures at Caribbean beaches slowly increase in line with climate change, then this will lead to a serious reduction in male hatchlings.

If these endangered sea turtles are going to survive in the long-term then not only do we need to protect their preferred nesting habitat, we also need to ensure that the potential nest sites have the correct temperature range.

Centro Ecologico Akumal and Operation Wallacea have now broadened the scope of the turtle nest monitoring project to include the placement of data loggers inside the nests in order to record ambient temperature during incubation. These data may then be matched to the nest site characteristics, hatchling success and sex ratios.

The team is currently raising funds to purchase a large number of data loggers to be used for the upcoming nesting season this summer. More information about the project and the option to make a donation are available from the website

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