Sea turtles are marine reptiles found across tropical and subtropical waters globally. Many people wonder about their seasonal behaviors, specifically if they hibernate during colder periods or if they undertake long journeys.
The Reality of Sea Turtle Migration
Sea turtles exhibit impressive migratory patterns, a primary response to environmental changes. They travel vast distances, often thousands of miles, between foraging and nesting grounds. For example, loggerhead hatchlings embark on transoceanic migrations across the Atlantic, and adult loggerheads from Japan migrate nearly 8,000 miles to feeding grounds off Baja California, Mexico. These journeys are for essential life cycle needs, including seeking food and returning to warmer waters for breeding and nesting.
Their navigation abilities are remarkable. Sea turtles detect the Earth’s magnetic field, using it as a compass and map to pinpoint locations. This “magnetic map” allows them to return to specific feeding areas and natal beaches for egg-laying. Environmental cues like water temperature changes also signal the start of migration.
Understanding Sea Turtle Dormancy
Sea turtles do not truly hibernate in the mammalian sense, but they can enter a state of reduced activity known as brumation. Brumation is a dormant period for reptiles where their metabolism slows significantly in response to cooler temperatures and decreased daylight. This state helps conserve energy when food is scarce or temperatures are uncomfortably cool, but not life-threatening. During brumation, a turtle becomes lethargic and may not eat, drink, or move for several weeks, though they may occasionally stir to drink water.
While some sea turtle populations migrate to warmer regions, others may exhibit brumation, especially in areas where water temperatures remain cool but stable enough for survival. This behavior allows them to endure periods when conditions are not optimal for foraging. However, there is little evidence that sea turtles remain underwater for the entire winter during brumation, unlike some freshwater turtles.
Responding to Extreme Cold: Cold-Stunning
Cold-stunning is a severe hypothermic reaction sea turtles can experience when exposed to rapidly cooling water temperatures. Unlike brumation, which is a controlled adaptive behavior, cold-stunning is an emergency. It occurs when water temperatures drop below 50 degrees Fahrenheit (10 degrees Celsius). When cold-stunned, turtles become weak, lethargic, and disoriented, losing the ability to swim effectively.
This condition makes them vulnerable to risks, including being washed ashore, drowning, predation, or boat strikes. Symptoms include a decreased heart rate, reduced circulation, and eventually shock, pneumonia, or frostbite. Cold-stunning events can affect hundreds or even thousands of turtles, particularly in shallow bays where water temperatures can fall quickly and trap them. Rescue efforts are crucial, with organizations and volunteers working to locate, rehabilitate, and release cold-stunned turtles back into warmer waters.