General Turtle Behavior
In general, turtles are solitary animals that spend their time diving and swimming, making it difficult to study them. They rarely interact with each other except for mating. However, olive ridley turtles can be observed nesting in groups. Although a large group of turtles may gather, it is rare to find them interacting.
Due to the difficulty of studying turtles in the open sea, much about their behavior remains unknown. After several decades of research, including observations in the open sea, some clues about their routines and behaviors such as courting, mating, and nesting have been uncovered.
DAILY ACTIVITIES
Turtles are known to eat and rest (sleep) in their daily routine. During the nesting season, research conducted in the southeastern United States found that loggerhead turtles have a regular pattern between their nesting beaches and coral areas in the sea. Researchers believe mating and feeding occur in these coral areas. When not in the nesting season, turtles may migrate hundreds to thousands of miles. Turtles may sleep on the surface of the sea or underwater in rocky areas near the shore. Many divers report finding turtles sleeping under crevices in rocky areas. Meanwhile, hatchlings tend to sleep by floating, often with their front flippers placed behind their carapace.
COURTING AND MATING
The courting and mating period for most turtles is believed to occur only during a brief “receiving” period, which happens early in the nesting season. After that, female turtles come ashore, while male turtles rarely come ashore once they leave the beach where they hatched. During mating, male turtles may court female turtles by caressing their heads or gently biting their neck or rear flippers. If the female does not move away, the male turtle will position himself behind the female’s carapace, holding the top of the female’s carapace with claws on his front flippers. Then, the male will bend his long tail around the female’s carapace to copulate.
Females observed on nesting beaches may have scratches on their carapace, possibly even bleeding. These wounds may have been caused by the male attempting to attach his flippers to the female’s carapace. Copulation occurs both on the surface of the sea and underwater. Sometimes, multiple males compete for mating with the female, even fighting among themselves. Researchers also report that male and female turtles can be very aggressive during this time. A female may mate with multiple males and store their sperm for several months. When the female eventually lays eggs, it is likely that the eggs have been fertilized by more than one male. This behavior contributes to the genetic richness of the population.
NESTING, INCUBATION, AND HATCHLING EMERGENCE
Very little is known about why turtles only nest on certain beaches and not others, even though the beach conditions may be the same. This distribution of nesting sites may reflect historical factors, such as temperature, beach profile, and the presence of predators, which were once suitable for turtles. Recently, human activity has affected some nesting areas. Erosion has occurred due to the installation of wave-break concrete or the construction of jetties, artificial lighting, and changes to beach conditions, all of which affect previously natural beach environments. These changes may affect future nesting patterns. A better understanding of where, when, and how turtles nest will enhance our ability to protect their nesting habitats.
NESTING BEHAVIOR
Only female turtles nest, and this is generally done at night. The turtle will come ashore and crawl, occasionally stopping to look around. Sometimes, she will crawl towards the beach but, for reasons not fully understood, will return to the sea and abandon nesting. This is called a “false crawl,” which can happen naturally or due to human disturbances, causing the turtle to feel unsafe. At least, female turtles nest twice in a season, while other individuals (species) may lay eggs once or even up to ten times. Turtles are slow on land, and the egg-laying process is exhausting for them.
LAYING EGGS AND COVERING THE NEST
Once the female turtle finishes digging the nest, she will lay her eggs there. One or two eggs may fall simultaneously, with mucus secreted during the process. The number of eggs varies between 50 and 150 eggs, depending on the species. Since turtle eggs have soft shells, they do not break when the female turtle drops them into the nest. The flexibility of the eggs allows the turtle to carry more eggs in her body. The female turtle may appear to shed tears, but she is merely secreting excess salt from her body.
Many people believe that a turtle laying eggs is in a trance-like state and is safe to “disturb.” This is not entirely true, as some turtles will abandon the egg-laying process and leave the nest if they feel unsafe due to disturbances. For this reason, it is best not to disturb turtles during egg-laying. After all the eggs are fully laid in the nest, the female turtle will cover the hole with sand using her back flippers. Slowly, with her front flippers, she will cover the body pit (hole in the sand for the turtle’s body) to conceal the nest. By scattering sand in all directions, it makes it difficult for predators to find the nest. Once she finishes camouflaging her nest, the female will return to the sea to rest before either nesting again during the same season or migrating. Once the turtle leaves the nest, she will not return to check on it.
INCUBATION
Incubation lasts for an average of 60 days, but the temperature during incubation can influence this period. In general, the warmer the temperature of the nest, the faster the development and hatching. Cooler nests tend to produce male hatchlings, while warmer temperatures increase the ratio of female hatchlings.
HATCHLING EMERGENCE
Unlike baby crocodiles that need help from their mothers, hatchlings must emerge from the nest on their own. To break through the egg shell, hatchlings use a sharp egg tooth called a “caruncle.” The caruncle is an extension of the jaw and will disappear after the hatchling hatches. The process of hatchlings emerging from the nest takes several days. Typically, hatchlings will emerge at night or when the temperature begins to cool. Once they decide to leave the nest, they will “burst” out simultaneously. The hatchlings’ orientation is toward the brightest part of the horizon, and once they identify it, they will quickly move toward the sea.
If they fail to get to the sea quickly, their chances of drying out or being preyed upon by predators like birds and ghost crabs increase. Once they reach the water, they will swim tirelessly for miles, where they will be carried by ocean currents and seaweed, which will protect them for several years before they return to the same beach. There are many challenges for hatchlings at sea. Sharks, large fish, and circling birds all prey on them, and many die from ingesting tar and plastic debris. The challenges are so great that nearly only 1 in 1,000 hatchlings survive to adulthood.
MIGRATION AND NAVIGATION ABILITY
Turtles’ ability to migrate hundreds to thousands of kilometers from feeding grounds to nesting beaches is one of the most amazing phenomena in the animal kingdom. The fact that female turtles always return to the place where they hatched adds to this awe. Research on where and how turtles migrate has been a focus for experts for many years. The information they gather is vital for the development of conservation strategies for this species. We now know that turtles have migrated throughout their lives, beginning with a frenzied swim during the early stages of their life.
In the critical 48 hours after hatching, a hatchling must quickly swim from the beach to the open ocean, which is relatively safer from predators and where they can find food. Many hatchlings that hatch in the Atlantic and Caribbean swim toward strong Gulf currents, often filled with sargassum seaweed. Many young turtles find abundant food with relatively few predators. After spending several years in the Atlantic Ocean, hatchlings that have grown into adult turtles will “return” to the place where they were hatched.
Teenage turtles appear to spend time eating and growing in the beach habitat where they hatched. However, once they reach sexual maturity, they are believed to migrate to new feeding grounds. This becomes their primary feeding area throughout their lives, except during mating season. When it’s time for them to mate and lay eggs, both male and female turtles will migrate back to the nesting beaches. This migration occurs throughout their lives.
NAVIGATION
In the open ocean, turtles face strong currents, have average vision, and can only lift their heads a few inches above the surface of the water, often with no clear sign of land. Despite all these limitations, turtles are regularly able to travel long distances to find their tiny nesting habitats. How they do this remains one of the greatest mysteries in the animal kingdom, and efforts to find answers have been the focus of researchers for generations. The most widely accepted theory is that turtles succeed in migration because they can detect the angles and intensity of Earth’s magnetic field. By using both, turtles can recognize longitude and latitude, allowing them to travel almost anywhere. Early research has provided evidence that turtles can detect the Earth’s magnetic field. How they use this ability is still under investigation.
STUDYING TURTLE MIGRATION
Turtle migration behavior has posed several challenges for researchers working to fully understand this animal and how to protect it. Specifically, in order to provide adequate protection for turtles, we need to know where their habitats are, how they behave when they are there, and the routes they take during migration. Most researchers have worked on nesting beaches—for good reason. These areas are the easiest to access, and what happens on the nesting beach (the production of new turtles) is crucial to the survival of this endangered species. Conservation efforts are easier to carry out in nesting habitats.
However, it is important to know that out of all the places turtles spend their lives, they spend very little time on the nesting beaches. Nearly 90% of a turtle’s life is spent in the water, for feeding, mating, migrating, and doing things that humans have never witnessed. As a result, threats to turtles in the open ocean are the biggest challenge for turtle conservationists.
To fully protect turtles, the first step is to investigate their migration patterns and behavior in the water. Several methods have been employed by researchers to track their movements. One of the easiest ways is to place a metal tag on the turtle’s flipper when it comes ashore to nest. Each metal tag contains a code with numbers and letters and a message for anyone who finds it to report the turtle’s location. This way, researchers can gradually learn about the places where turtles can be found. Efforts now focus on reducing the number of turtles killed for their meat. The use of metal tags has provided valuable information, but many questions remain unanswered.
SATELLITE TELEMETRY
Researchers have recently used satellites to track turtles in the open ocean. Initially, a Sony Walkman-sized transmitter is attached to the carapace of an adult or juvenile turtle. The transmitter is glued to the back of the carapace, behind the head, and a unit with a flexible antenna will protrude above the surface of the water to send transmissions when the turtle comes up for air. A satellite passing overhead will send this information back to the researchers on Earth. After 8-10 months, the transmitter will stop working and detach from the turtle safely.
Using computer maps, researchers can determine where the turtles migrate, which routes they take, and how fast they swim. Once the map is filled with details, the characteristics of the turtle’s location can also be identified. After monitoring specific turtle populations, researchers continually learn about their main feeding areas and what threats they face in the open ocean. With this information, turtle conservationists can focus their efforts on key turtle habitats.
