Turtles die from a wide range of causes, from predation and disease to plastic pollution, fishing nets, and poor care in captivity. Despite their reputation for longevity, turtles face serious threats at every life stage. Only about 1 in 1,000 sea turtle hatchlings survive to adulthood, and both wild and pet turtles are vulnerable to specific dangers that often go unrecognized until it’s too late.
Predation and the Brutal Math of Early Life
For sea turtles, the most dangerous period is the very beginning. Hatchlings emerge from their nests, usually at nightfall to avoid daytime predators and heat exhaustion, and immediately face birds, crabs, raccoons, and fish during their scramble to the ocean. The vast majority never make it. Of those that reach the water, many are eaten in open ocean before they grow large enough to deter predators.
Young turtles eventually move to coastal foraging grounds where food is more abundant, but so are predators. They delay entering these areas until their body size gives them a better chance of survival. For freshwater turtles, the pattern is similar: eggs are raided by raccoons, foxes, and birds, and small hatchlings are easy targets for fish, herons, and snakes. Adult turtles have far fewer natural predators thanks to their shells, but alligators, sharks, and large birds of prey still take them.
Plastic Pollution and Ocean Debris
Plastic kills more sea turtles than most people realize. A large-scale analysis of over 10,000 necropsied marine animals found that 47% of sea turtles had ingested plastic, and 4.4% died directly from it. That’s the highest plastic mortality rate among the three groups studied, which also included seabirds and marine mammals.
The way plastic kills is straightforward: it blocks, punctures, or twists the digestive tract. Hard and soft plastics pose the greatest risk to sea turtles specifically. Turtles are thought to mistake plastic bags for jellyfish, a common prey item. Even when ingestion isn’t immediately fatal, plastic in the gut dilutes nutrition and can lead to slow starvation. For juvenile sea turtles, around 377 pieces of ingested plastic are associated with a 90% chance of death.
Commercial Fishing Bycatch
An estimated 250,000 turtles die every year as bycatch, caught accidentally in fishing gear meant for other species. Longlines, trawl nets, and gillnets all trap turtles, which drown when they can’t surface to breathe. This is one of the largest single sources of sea turtle mortality worldwide and affects all species, including critically endangered ones like the Kemp’s ridley.
Boat Strikes
Hundreds to thousands of sea turtles are struck by boats in the United States alone each year, and many of those collisions are fatal. In Florida, injuries consistent with vessel strikes show up in 20 to 30 percent of stranded sea turtles. Propeller cuts to the shell and skull are the most common injuries. Turtles that survive the initial impact often die later from infection or internal bleeding. Vessel strikes are one of the most common reasons sea turtles strand on U.S. beaches.
Fibropapillomatosis: A Growing Disease Threat
Fibropapillomatosis is a tumor-forming disease that primarily affects green sea turtles, though it appears in other species too. The tumors grow on skin, eyes, and internal organs including the lungs, kidneys, and liver. The disease is strongly linked to a herpesvirus called ChHV5, but the virus alone doesn’t seem to cause tumors. The immune status of the turtle, its genetics, and environmental conditions all play a role in whether the disease develops.
Some turtles recover on their own, and external tumors can sometimes be surgically removed. But when the tumor burden is high or tumors are found internally, the prognosis is poor. Over 60% of wildlife rehabilitation experts surveyed said internal tumors justify euthanasia, and about 31% said the same for severe external tumors. Tumors around the eyes are particularly devastating because they blind the turtle, making it unable to feed or navigate.
Chemical Pollutants and Oil Spills
Beyond plastic, turtles accumulate toxic chemicals from contaminated water and food. Heavy metals like cobalt, antimony, and manganese have been linked to acute inflammation and liver dysfunction in sea turtles found near polluted coastlines. PCBs, a class of industrial chemicals that persist in the environment for decades, can damage the immune system, cause anemia, and harm the liver.
Oil spills are another major threat. Exposure to crude oil and related compounds can cause serious health and reproductive problems, with the severity depending on the route of exposure, the turtle’s sex, and its life stage. Hatchlings and juveniles are especially vulnerable because of their smaller body size and the amount of time they spend at the ocean surface, where oil collects.
Rising Temperatures and Nest Failure
Turtle eggs develop in sand nests where temperature determines not just the sex of hatchlings but whether they survive at all. Continuous incubation at 34°C (about 93°F) kills all sea turtle embryos. Even at 33°C, some embryos develop malformations that prove fatal later in development. A natural green turtle clutch at Raine Island in Australia experienced 80% early embryo death after nest temperatures averaged 35.5°C during the first week.
On beaches with high-density nesting, the problem compounds. Nearby nests generate metabolic heat as embryos develop, raising the temperature for newly laid clutches around them. Conservation strategies like shading nests, irrigating sand, or spacing clutches farther apart can help bring temperatures down and improve hatching success. But as global temperatures rise, more nesting beaches are approaching or exceeding that 34°C lethal threshold.
Why Pet Turtles Die
Captive turtles face a completely different set of threats, almost all of them preventable. The three most common killers are metabolic bone disease, vitamin A deficiency, and respiratory infections, and they’re often connected to each other.
Metabolic bone disease develops when a turtle doesn’t get enough calcium, gets too much phosphorus, or lacks access to ultraviolet light. UV exposure is essential for turtles to produce vitamin D and absorb calcium properly. Without it, their shells grow misshapen and their bones deform. Affected turtles grow slowly and often never reach full adult size.
Vitamin A deficiency is extremely common in turtles fed monotonous diets, particularly those given only iceberg lettuce or feeder fish without variety. The deficiency causes a cascade of problems: swollen, infected eyelids that seal shut, ear abscesses, kidney failure, and a general collapse of the immune system. Once the eyes swell shut, the turtle stops eating entirely. Without treatment, it starves to death. Studies of captive terrapins have found widespread tissue damage in the eyes, liver, pancreas, and kidneys from vitamin A deficiency alone.
Respiratory infections are the third major killer and frequently develop as a secondary problem after vitamin A deficiency weakens the turtle’s defenses. Dirty tank water accelerates the problem. Signs include bubbles from the mouth or nose, wheezing, neck stretching, and open-mouth gasping. If the infection reaches the lungs, pneumonia develops, and the turtle may tilt to one side while swimming. These infections require injectable antibiotics to treat effectively, since giving oral medication to a turtle is extremely difficult.
The common thread for pet turtle deaths is husbandry. Proper UV lighting, clean filtered water, appropriate temperatures, and a varied diet that includes dark leafy greens and vitamin A-rich foods prevent the vast majority of fatal conditions in captive turtles.