Turtles, known for their ancient lineage and protective shells, often symbolize endurance and longevity. While many species can live for decades, they are not impervious to threats. Both wild and captive individuals face numerous hazards that can lead to injury, illness, and ultimately, death.
Environmental Hazards
Environmental factors significantly contribute to turtle mortality by disrupting their natural habitats and physiological processes. Habitat destruction, driven by urbanization and agriculture, diminishes the spaces turtles need for foraging, nesting, and overwintering. Coastal development, for instance, reduces suitable nesting beaches for sea turtles, directly impacting reproductive success.
Pollution poses another substantial threat, ranging from plastic debris to chemical contaminants. Turtles can ingest plastic, leading to intestinal blockages, malnutrition, and internal injuries. Oil spills and industrial runoff introduce toxic metals and chemicals into their environments, which can cause immunosuppression, organ damage, and reproductive issues.
Climate change also influences turtle survival through altered temperatures and rising sea levels. Warmer incubation temperatures affect the sex ratio of hatchlings, often producing more females, which can reduce reproductive opportunities. Rising sea levels erode nesting beaches, while extreme weather events like floods and droughts can destroy nests and alter freshwater habitats. These environmental shifts can also impact food sources.
Health Complications
Internal and biological factors, including diseases and nutritional deficiencies, are common causes of turtle mortality, especially in captive settings. Respiratory infections are prevalent, often caused by bacteria or viruses, and can manifest as nasal discharge, lethargy, and open-mouth breathing. Shell rot, another common ailment, results from bacterial or fungal infections that degrade the shell, while abscesses can form as pus-filled swellings.
Metabolic bone disease (MBD) is a significant concern, particularly for pet turtles, stemming from an imbalance of calcium and phosphorus, or insufficient ultraviolet (UV) light exposure. This condition can lead to misshapen shells, deformed bones, and stunted growth. Vitamin A deficiency, or hypovitaminosis A, often occurs when turtles are fed improper diets, weakening their immune systems and making them susceptible to other infections.
Malnutrition can also arise from an inadequate diet in captivity, leading to organ failure or systemic weakness. The general decline associated with old age can make turtles more susceptible to illness and injury. While turtles are known for their longevity, reproduction and survival can decline with advanced age in wild populations.
Human-Related Dangers
Human activities present direct and indirect dangers that significantly impact turtle populations worldwide. Road mortality is a substantial threat, particularly for semi-aquatic and terrestrial turtles that frequently cross roads during their annual movements, such as seeking food, mates, or nesting sites. Female turtles, especially those carrying eggs, are highly vulnerable as they often travel long distances to lay clutches.
Intentional harm and poaching also contribute to turtle deaths. The illegal trade in turtles for pets, food, or traditional medicine leads to thousands of individuals being harvested annually, including eggs and adult turtles.
Entanglement in fishing gear and marine debris is a widespread issue. Discarded fishing nets, lines, and other plastic waste, often referred to as “ghost gear,” can trap turtles, restricting their movement, preventing them from surfacing to breathe, and leading to drowning, starvation, or severe injuries. Incidental capture, or bycatch, in commercial and recreational fishing operations accounts for a large number of turtle deaths globally.
Predation and Accidental Injuries
Turtles, particularly in their early life stages, face various threats from other animals. Eggs and hatchlings are highly susceptible to predation by a range of species. Common predators of turtle nests include raccoons, foxes, coyotes, skunks, and opossums, which can dig up and consume eggs. Birds like gulls and crows, as well as crabs, also prey on hatchlings as they emerge from nests and make their way to water.
Once in the water, juvenile turtles remain vulnerable to large fish, such as snapper and grouper, while larger sharks and killer whales can occasionally prey on adult sea turtles. While adult turtles have robust shells that deter many predators, some powerful animals, like jaguars or large crocodilians, are capable of attacking them.
Accidental injuries can also be fatal. These might include falls from elevated areas in their habitat or getting trapped in confined spaces. Encounters with other wildlife, even if not predatory, can result in severe physical trauma that compromises a turtle’s ability to survive.