Sea Turtles in Cabo Verde
Sea turtles have been roaming the Earth for over 150 million years. During this time seven different species evolved separately and became what we know today as sea or marine turtles. They have played, and still play, an important role in our oceans, maintaining different marine ecosystems healthy and in balance. However, during the last 100 years sea turtles are facing different anthropogenic threats that are jeopardising their survival. The Red List of Threatened Species from the IUCN (International Union for the Conservation of Nature) includes 6 of the 7 species of sea turtles. The status of the other species, the Flatback turtle, is unknown.
In Cabo Verde, five different species of sea turtles have been observed: Leatherbacks, Greens, Loggerheads, Hawksbills and Olive Ridley. From those, the loggerhead is the only species nesting regularly. The archipelago supports one of the world’s largest nesting aggregations of loggerhead sea turtles, and the only major nesting area for loggerhead turtles along the entire eastern Atlantic coast. This is fact is more impressive given the broad distribution of this species around the globe.
An average adult Loggerhead turtle in Cabo Verde:
Although in 2015 the global status for the Loggerhead sea turtles was downgraded from endangered to vulnerable, the North East Atlantic subpopulation (Cabo Verde) was left as endangered. The IUCN Marine Turtle Specialist Group listed in 2011 this subpopulation as one of the eleven most threatened populations of sea turtles in the world. Given the high philopatry of female sea turtles (fidelity to their breeding site) and the extremely slow dispersion to different nesting sites, Cabo Verde is essential for the reproduction of loggerhead turtles.
In Cabo Verde the consumption of sea turtle meat is a long-standing tradition, as is the consumption of eggs on some islands and the hunting of males for aphrodisiacs. In 1987 the hunting of sea turtles was banned during the nesting season in Cabo Verde; in 2002 it was banned during the whole year; and in 2005, possession, hunting, consumption and exploitation of sea turtles and their eggs became explicitly prohibited by law. In 2018 the Government, with the support of all political groups, is expected to approve a new law that will criminalise all these ilegal activities, and will settle the foundations for the sea turtle conservation in Cabo Verde. Although the Cabo Verdean government regulations, the killing of females that come ashore to lay their eggs is still a problem seen across the whole country.
The Life of Sea Turtles
Sea Turtles have a long and complicated life cycle. They will only reach maturity after 15 – 25 years, and when they do, they will only breed every 2-3 years until they are 45 – 50 years old. Early stages are very vulnerable. The eggs are laid under the sand and are exposed to many natural and anthropogenic threats. There is no maternal care, and this means that the new-born turtles (or hatchlings) will start their life journey alone. Hatchlings and juvenile turtles will face predation and other threats, and even adult turtles will battle against poaching and marine pollution. In the end, only 1 in a 1,000 hatchlings will become adults.
Probably, one of the most amazing things about sea turtles is their ability to find their way back after spending 20 years around the ocean. It is mostly accepted that they can follow the earth’s magnetic fields to find the same location where they hatched, although other mechanisms may also help. They can also move to new nearby locations, always looking for quiet places with good nesting conditions.
Sea turtles don’t have sexual chromosome like mammals. Instead, their sex is determined by the temperature of incubation of the eggs, something called TDS (Temperature-Determined Sex). Nests that were incubated at lower temperatures may create more males, while warmer temperatures will increase the female's numbers. Although the pivotal temperature could vary within different populations, it is agreed that 29ºC would mark the balanced incubation temperature.
The Importance of Sea Turtles
Sea turtles find themselves on the top of the food chain of most marine ecosystems. Like all megafauna, they help to keep the oceans in healthy conditions and intervene in different steps of the food chain. The disappearance of sea turtles and other keystone species from our oceans, would disrupt the balance of marine ecosystems and, ultimately, would have a huge social and economic impact for humans.
Navigate through this diagram of a marine ecosystem to learn more about the ecological importance of sea turtles:
Source of Food
Sea turtles are also prey for some animals. As adults, they will be a source of food for sharks and orcas. While hatchlings will feed many different animals like fish, crabs, sharks, seabirds and even other terrestrial mammals. Remember, only 1 in a 1,000 baby turtles will survive!
Some species of sea turtles feed on sponges (hawksbills) and algae (greens) that compete with coral for space and suffocate them. Keeping their numbers under control allow coral to grow and expand. Don’t forget that coral reefs are one of the most important ecosystems on earth!
Green turtles are the gardeners of the oceans. They feed on seagrass keeping it healthy, just like we do with lawnmowers. Seagrass beds are nurseries for many different species of fish, giving them shelter against predators. They also stop the erosion against storms of shallow seabeds.
Sea turtles provide habitat for many different small animals, called epibionts, that live in their carapaces and skin. Sea turtles also provide food to some species of fish and shrimps, in what we call “cleaning stations”. They will clean the turtle carapaces from epibionts, keeping a balance of comfort for the turtles.
Recycle of Nutrients
Loggerheads have incredibly strong jaws capable of crushing seashells. Through the small bits of shells and their faeces, sea turtles increase the rate of nutrient recycling in benthic and ocean bottom ecosystems.
Source of Food
Hatchlings form part of the diet of different animals like fish, crabs, sharks, seabirds and even other terrestrial mammals. Remember, only 1 in a 1,000 baby turtles will survive!
Protection of Dunes
Sea turtles are also important outside the water. The egg shells and unhatched eggs from their nests will nourish the vegetation cover of the dunes. Vegetation prevents the erosion of the dunes caused by wind, strong tides and waves. Dune ecosystems are very important to mitigate the impacts of Climate Change!
Recycle of Nutrients
Leatherbacks are one of the few predators of jellyfish. Jellyfish, at the same time, eat fish larvae. The lack of leatherbacks will increase blooms of jellyfish, that could decrease certain populations of fishes, some of them of commercial interest.
Sea turtles are, therefore, very important for different ecosystems and many other species depend on them. Another important aspect of sea turtles is that they can help prevent some impacts of Climate Change in coastal communities. Having strong and healthy dune systems and coral reefs will prevent coastal areas to get flooded due to sea level rise and due to an increase of extreme weather events like hurricanes.
If we think from a broader perspective we will see that all the roles that sea turtles play in the marine ecosystem have some direct or indirect benefit for humans. But they also bring some important socioeconomic impact on coastal communities where they nest. Through ecotourism, conservation and research, hundreds of Cabo Verdeans are employed every year. In 2016 the network for sea turtle conservation of Cabo Verde, TAOLA, led by the director of Project Biodiversity, prepared a study on the socioeconomic impact of sea turtles in Cabo Verde. In 2016 almost 900,000€ were generated through “turtle watching” excursions and through the employment of staff from all the NGOs working on the field in Cabo Verde. Nowadays this number is expected to have increased considerably.
6 out of 7 species of sea turtles are threatened of extinction. But who is threatening them? Sadly, humans are responsible for 99% of species extinction in the world. Recent studies found out that the current extinction rate is between 1,000 and 10,000 times higher than the “normal” extinction rate (background rate). While before only 0,1 species from every million went extinct every year, now this number is at least 100 in every million species.
With sea turtles happens the same. Human-driven threats, or anthropogenic threats, are the main causes for the decrease in their populations. In Cabo Verde, as well as in many other places in the world where turtles nest, we can list those threats as following: