Understanding The Movements Of Hawksbill Sea Turtles
It is important that researchers and conservationists have a clear understanding of the movement, distribution and habitat preferences of endangered animals during their most vulnerable life stages to ensure proper conservation and management of the species. The loss of global biodiversity due to extinction is an irreversible problem that urgently needs addressing, especially for Critically Endangered animals, like the Hawksbill sea turtle.
About Hawksbill Sea Turtles
Hawksbill sea turtles (Eretmochelys imbricata) are found in tropical and sub-tropical regions throughout the world’s oceans. They get their common name from their beak-like mouth, which is similar to a beak of a hawk. They use this unique structured mouth to reach into rock crevices to look for their favorite food item – sea sponges.
Hawksbill sea turtles were once very abundant and found in almost all the tropical oceans across the world. In the past 150 years, it is estimated that over nine million hawksbill turtles were killed. Their shells are a valuable commodity and used for luxury items such as jewelry and trinkets. Other threats facing this Critically Endangered turtle species include accidental bycatch in fisheries, illegal trafficking of turtle eggs and the turtles themselves for food, loss of nesting beaches due to coastal development, predation of eggs and juveniles by introduced species, and the ongoing (and illegal) shell trade. This species has been classified as globally Critically Endangered on the IUCN Red List of Threatened Species, and some populations – particularly those in the Northeast Indian Ocean, East Atlantic Ocean, West Pacific Ocean, and Eastern Pacific Ocean – are more threatened than others.
The Eastern Pacific population can be found from Mexico to Ecuador. This population is the most threatened hawksbill sea turtle population, with less than 600 nesting females left. This population nests primarily in Nicaragua and El Salvador, as well as Costa Rica and Ecuador. Individual turtles have also been spotted in the waters of Mexico, suggesting that it is an important area for juveniles and adults. The movements between nesting beaches and foraging areas is not yet well known, and it is important that studies focus on the movement patterns of hawksbill sea turtles.
Monitoring Movements of Hawksbill Sea Turtles in Mexico
Conservation of hawksbill sea turtles focus many on protecting their nesting sites, however the juvenile life stages of sea turtles are crucial for their survival. A team of researchers set out to study the movement patterns of hawksbill sea turtles in Mexico, and published their findings in the journal of Global Ecology and Conservation.
To do this, the team examined sea turtle foraging areas in the Gulf of California, Mexico, along the Baja California Peninsula. They specifically studied the home range and movement of 12 individual turtles between 2014 and 2019. The sea turtles were captured to allow for tagging with satellite tags, and measurements of the turtles were taken.
The researchers wanted to identify the home ranges of the turtles, which is defined as the area used by the animal to conduct its daily activities. To determine the home ranges, both GPS and satellite tags were used and movement (or lack thereof) of the turtles were recorded. The tags showed that all the turtles observed had short distance movements, and some of the home ranges overlapped, however the core areas within their home ranges were separate. The individual turtles were observed to remain within their home ranges for months and years. The only exception was one turtle which had two core areas.
Determining Habitat Type and Protection of Habitats
The researchers found that five of the twelve tagged turtles preferred mangrove estuaries for their core areas. Four turtles used rocky reef habitats that were in close proximity to the mangroves. Two turtles preferred a coral reef habitat, and one turtle exclusively used the rocky reef habitat.
The home ranges of the turtles fortunately overlapped with national marine protected areas and fish refuges. Six of the 12 tracked turtles remained completely within these protected areas, while the others’ ranges overlapped partially with marine protected areas.
Value of the Study
This study that focused on movement patterns and habitat use of hawksbill sea turtles in the Gulf of California is one of few studies into long term movements and foraging of hawksbill sea turtles in the Eastern Pacific Ocean. It is the first spatio-temporal analysis of hawksbill turtle movements within the Gulf of California. The study also indicates the value of mangrove habitats for hawksbill turtles, which should be taken into consideration when it comes to conservation of hawksbill sea turtle populations.
It is generally assumed that long-term residency of large marine animals in home ranges or foraging habitats is associated with consistent food availability. It is therefore likely that the high residency of the turtles in the study was due to foraging activities, and that the mangrove and rocky reefs close to the mangroves are important foraging areas for hawksbill sea turtles in the Gulf of California.
It is important that the impact of legally declared marine protected areas on hawksbill sea turtle populations are understood, to improve future conservation measures for this species. Within the study area (outside of the national marine protected area), hawksbills are vulnerable to accidental bycatch by small-scale fisheries, as well as vessel strikes and habitat degradation, and there is the potential to expand the marine protected areas network to include important foraging areas for this critically endangered species.
The study on movement patterns of hawksbill sea turtles in the Gulf of California provides the first detailed analysis of this population’s and foraging areas. The results of the study highlight the importance of spatial protection through marine protected areas as fish refugia. It is evident that hawksbill turtles are dependent on coastal areas and mangroves, and knowing this could help re-establish a thriving hawksbill sea turtle population in the Eastern Pacific.
Identifying important priority areas for conservation is just the first step. Adaptable management plans must be used in conjunction with legal protection, such as plans for sustainable fisheries management and protection of endemic species. Conservation of the critically endangered hawksbill sea turtle will only be possible if there is collaboration between communities, government and non-governmental organizations.