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Loggerhead Sea Turtle: The Most Fascinating Guest on Sal
The loggerhead turtle (Caretta caretta) is a type of sea turtle known for its large size, distinct reddish-brown shell, and powerful jaws. They are among the largest species of sea turtles. The adults reach an average length of around 3.5 feet to 1 meter. With a weight ranging from 200 to 400 pounds, or 90 to 180 kilograms, they are already true giants among the turtle family. And some exceptional individuals can grow even larger!
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The Loggerhead Sea Turtle’s Appearance
The loggerhead turtle gets its name from its large head, which is, indeed, relatively massive compared to the heads of other sea turtle species. Also worth noticing are its strong jaws with powerful beak-like mouths, adapted for crushing and grinding the hard shells of their prey. Turtle’s shell, also known as the carapace, is slightly heart-shaped and characterised by a reddish-brown colour. It features a series of large, non-overlapping scutes (scales) that provide protection. Loggerhead turtles have four strong flippers, which they use for swimming and manoeuvring through the water.
What’s also interesting is the fact that their front flippers have two claws each, designed, among other things, for digging. In comparison, the rear flippers are much larger and more paddle-like in shape. Which makes them excellent tools for fast swimming.
Loggerhead Turtle (caretta caretta) in Cape Verde
Nesting
Cape Verde is an important nesting site for loggerhead turtles in the Atlantic Ocean. Islands such as Boavista, Sal, and Maio are known for their nesting beaches. There, Loggerhead turtles typically nest from June to September, with peak nesting activity occurring in July and August. Female loggerhead turtles dig nests on the sandy beaches to lay their eggs. They exhibit nesting site fidelity, returning to the same beaches where they were born to lay their eggs.
Threats
Like many other sea turtle populations, loggerhead turtles in Cape Verde face various threats. These include habitat degradation, beach erosion, predation of eggs and hatchlings, entanglement in fishing gear, pollution, and climate change.
Conservation Efforts
Conservation organisations in Cape Verde are working to protect sea turtles and their nesting grounds. Efforts include monitoring nesting activity, conducting research on nesting populations, implementing nest protection measures, and raising awareness among local communities and tourists.
Research and Studies
Scientific studies have been conducted in Cape Verde to gain a deeper understanding of various aspects of loggerhead turtle ecology and conservation. For example, research has been done on the impact of fungal infections on loggerhead turtle nesting success, as well as the biochemical indices and life traits of loggerhead turtles in Cape Verde.
Please note that specific and up-to-date information on loggerhead turtles in Cape Verde can be found through scientific research articles, conservation organisations, and local authorities dedicated to sea turtle conservation in Cape Verde.
Habitat
Loggerhead turtles are found in various oceans and seas worldwide, preferring warm and temperate waters. They spend most of their lives in the open sea but come ashore to nest and lay their eggs on sandy beaches. Loggerheads occupy waters with surface temperatures ranging from 13.3–28 °C (56–82 °F) during the non-nesting season and from 27–28 °C (81–82 °F) while nesting. Water temperature is crucial because it affects the sea turtle’s metabolic rate. Younger loggerheads are more cold-resistant and are fine until temperatures drop below 9 °C (48 °F). The loggerheads’ migration helps to prevent instances of cold-stunning. Higher water temperatures cause an increase in metabolism and heart rate.
Diet
The loggerhead sea turtle is omnivorous, feeding mainly on bottom-dwelling invertebrates, such as gastropods, bivalves, decapods, and horseshoe crabs. It can also eat sponges, corals, sea pens, polychaete worms, tube worms, sea anemones, cephalopods, barnacles, brachiopods, amphipods, isopods, Portuguese men o’ war, insects, bryozoans, hydrozoans, sea urchins, sand dollars, sea cucumbers, starfish, tunicates, fish (eggs, juveniles, and adults), hatchling turtles (including members of its opecies!), algae, and vascular plants. During migration through the open sea, loggerheads eat jellyfish, floating molluscs, floating egg clusters, squid, and flying fish.
Loggerhead Sea Turtle’s Behaviour
Loggerhead sea turtles observed in captivity and the wild are most active during the day. In captivity, loggerheads’ daily activities primarily consist of swimming and resting underwater. While resting, they spread their forelimbs to a position similar to midstroke swimming. They remain motionless with eyes open or half-shut and can be easily alerted during this state. At night, captives sleep in the same pose with their eyes tightly shut and are slow to react.
Life Underwater
Loggerheads spend up to 85% of their day submerged, with males being the more active divers than females. The average duration of dives is 15–30 minutes, but they can stay submerged for up to four hours. Juvenile loggerheads and adults differ in their swimming methods. A juvenile keeps its forelimbs pressed to the side of its carapace and propels itself by kicking with its hind limbs. As the turtle matures, its swimming progressively changes to the adult’s alternating-limb method. It depends entirely on this method of swimming from the age of one.
Significant threats to the life of Caretta caretta and other sea turtles
Climate change and various human activities have negatively impacted loggerhead sea turtle populations. Development and degradation of beaches and coastal islands have destroyed nesting beaches or interfered with nesting activities.
Nesting Threats
Artificial lights on beaches may cause females to return to the ocean without laying eggs. Hatchlings disoriented by the lights sometimes crawl toward highways and get run over. Nesting success decreases due to the increasing number of nest predators, such as raccoons, which thrive in response to human development. Adults sometimes drown in shrimp nets or get killed by boat traffic. Floating plastic bags and balloons, which resemble jellyfish, are also a problem. When consumed, they block the gastrointestinal tract and can ultimately lead to the turtle’s death. Entanglement in discarded fishing nets is also a threat to injury or death.
Loggerhead sea turtles are:
Hunted for meat and eggs
In the past, people intensively hunted loggerhead sea turtles for their meat and eggs. Such situations decreased due to worldwide legislation, but some people still consume turtle meat and eggs in many countries. It’s worth mentioning that eating turtle eggs or meat can cause serious illness due to harmful bacteria and high levels of toxic metals.
Caught in fishing nets
Fishing gear is the biggest threat to loggerheads in the open ocean. They often become entangled in longlines or gillnets. They also become stuck in traps, pots, trawls, and dredges. When caught in this unattended equipment, loggerheads risk injury or drowning. Turtle excluder devices for nets and other traps reduce the number of being accidentally caught.
Mistaking plastic for food
Nearly 11 million metric tons of plastic are released into the ocean annually – this number is projected to increase to 29 million metric tons by 2040. Loggerheads may mistake the floating plastic for jellyfish, a common food item. They ingest this floating debris, including bags, sheets, pellets, balloons and abandoned fishing lines.
The ingested plastic causes numerous health concerns, including intestinal blockage, reduced nutrient absorption and malnutrition, suffocation, ulcerations, or starvation. Ingested plastics release toxic compounds, including polychlorinated biphenyls, which may accumulate in internal tissues. Such toxins may lead to a thinning of eggshells, tissue damage, or deviation from natural behaviours.
Confused by artificial lights
Artificial lighting discourages nesting and interferes with the hatchlings’ ability to navigate to the water’s edge. Females prefer nesting on beaches free of artificial lighting. On many shores, nests are often clustered around tall buildings, perhaps because the constructions block out the night light sources. Loggerhead hatchlings are programmed to migrate toward the reflection of the moon and starlight over the ocean.
Still, they are confused by the brighter artificial light and mistakenly navigate inland, away from the protective waters, which expose them to dehydration and predation as the sun rises. Artificial lighting causes tens of thousands of hatchling deaths per year.
Loosing access to their nesting spots
Destruction and encroachment of habitat by humans are other threats to loggerhead sea turtles. Optimum nesting beaches are open-sand beaches above the high-tide line. However, beach development deprives them of suitable nesting areas, forcing them to nest closer to the surf. Urbanisation often leads to the siltation of sandy beaches, decreasing their viability.
Construction of docks and marinas can destroy near-shore habitats. Boat traffic and dredging can degrade habitat and injure or kill turtles when boats collide with them at or near the surface.
Reacting to the temperature change
Annual variations in climatic temperatures can affect sex ratios, as loggerheads exhibit temperature-dependent sex determination. High sand temperatures may skew gender ratios in favour of females. Nesting sites exposed to unseasonably warm temperatures over three years produced 87–99% females. It raises concern over the connection between rapid global temperature changes and the possibility of population extinction.
Temperature and New Constructions
A more localised effect on gender skewing comes from the construction of tall buildings (reducing sun exposure). It lowers the average sea temperature, resulting in a shift in gender ratios that favours the emergence of male turtles. The construction of new thermal power stations can raise local water temperatures, which is also considered a threat.
Endangered by natural disasters
Tropical Cyclones have a significant impact on hatchling loss. The associated storm surges push water higher up the beach, flooding the nest and drowning the embryos. High wave action may erode sand and expose the eggs to drying and predation. The current trend of rising sea surface temperatures and the increase in both the number and intensity of tropical cyclones poses a growing threat to turtle populations.
Conservation Efforts
Loggerhead turtles are remarkable marine creatures with a crucial role in maintaining the balance of aquatic ecosystems. Conservation efforts, including the establishment of protected nesting areas and the adoption of sustainable fishing practices, are essential to ensuring the survival of this magnificent species.
The International Union for Conservation of Nature considers the loggerhead sea turtle species vulnerable. Nine distinct population segments are protected under the Endangered Species Act of 1973, with four classified as threatened and five as endangered. CITES Appendix I prohibits commercial international trade of loggerheads or derived products.
Sea Turtle Conservation Challenges
Since the loggerhead occupies such a broad range, successful conservation requires efforts from multiple countries. During the nesting season, workers and volunteers search the coastline for nests, while researchers also venture out at night to locate nesting females for tagging studies and collect barnacles and tissue samples. Volunteers may, if necessary, relocate the nests to protect them from threats, such as high spring tides and predators, and monitor the nests daily for disturbances.
After the eggs hatch, volunteers uncover and tally hatched eggs, undeveloped eggs, and dead hatchlings. Any remaining live hatchlings are released or taken to research facilities. Typically, those who lack the vitality to hatch and climb to the surface die.
Bibliography / Sources
- The loggerhead sea turtle (Caretta caretta) on Sal Island, Cape Verde: nesting activity and beach surveillance in 2009 by Silvia P P Lino, Euclides Goncalves, Jacquie Cozens on ResearchGate;
- Information About Sea Turtles: Loggerhead Sea Turtle on Sea Turtle Conservancy;
- Loggerhead sea turtle (Caretta Caretta) on Wikipedia, The Free Encyclopedia;
- Map: Geographical Range of Loggerhead Sea Turtle – Caretta caretta (Linnaeus, 1758), California Herps.
