TURTLE PARTS 8: SUBADULT AND ADULT

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The subadult stage of a sea turtle’s life lasts from the time they reach one year of age until they are capable of reproduction (adulthood) which may take 12 to 25 years depending on the species. Adult sea turtles are believed by some to live to be 90 years or more. Subadulthood appears to begin with the young turtles leaving the relative safety of the floating sea grasses.

At exactly what stage in their development the turtles abandon the grass drifts altogether is not certain, but their
increased rate of growth would suggest that it is during this time period. Food sources located within the grasses are not believed to be substantial enough to support the increased rate of growth exhibited during subadulthood. As the turtles begin this stage of their life they are about the size of a coffee cup saucer and grow to the size of a large Frisbee within 5 years. The turtles continue to grow at a rate that has some species reaching a mature size of over 125 centimeters in length and over 90 centimeters wide in just 7 additional years. To support this rapid rate of growth, the turtles must now begin migrating to feeding grounds located closer to shore.

What constitutes a suitable feeding ground depends on what species of sea turtle you are concerned with and what stage of development the turtle is at. Sea turtles feed on a wide variety of both pelagic (open ocean) and coastal water organisms as subadults and adults. Almost every type of crab imaginable and other crustaceans, tunacates, mollusks, jellyfishes and fish make their way into the stomach of a sea turtle. It seems that most species, except the green, have the same diet both as subadults and adults. The proportional amount of each type of foodstuff does change as the turtles grow older, but with greens this proportional change is drastic. They go from an omnivorous (both animal and plant matter) diet as subadults to a strictly herbivorous (plant matter) diet as adults, feeding on sea grasses and algae that grow in the shallow coastal flats of warm water regions. A great majority of the sea turtle’s life is spent in search of and consuming food. The remainder of their time is spent resting and migrating from feeding grounds to mating and nesting sites.

Subadult and adult sea turtles will generally rest at the surface of the water. They are also known to rest underwater, by lodging themselves under some sort of structure or digging themselves into the ocean floor. Exactly how long the turtles can remain under water resting is not known and most likely varies from species to species. However, it is known that most species can spend approximately 40 minutes underwater while swimming. With body functions slowed, it seems logical to presume that turtles can remain submerged longer than 40 minutes when they are resting. The amount of time spent resting can not be too great, because sea turtles migrate such great distances.

Distances covered by sea turtles migrating between feeding grounds and mating and nesting sites can be greater than 6,000 miles. They often traverse entire oceans. Swimming such distances shows incredible stamina and an even greater navigational ability. The turtle’s ability to locate these sites for mating and nesting is truly incredible and not yet fully understood. It is presently believed that the turtles use a combination of physical markers, mineral imprinting and some sort of biological directing device to find these areas again. Further research into this subject will hopefully solve this mystery. Now that the turtles have migrated this far, it is time for mating to commence.

Just prior to mating the turtles begin congregating en masse in waters adjacent to their nesting beach. This three or four week period, before the female first emerges to nest, is believed to be the only time that she is receptive to mating. Females generally mate with several males during this period of time. This ensures that the eggs will be fertilized by several males and likely assists in keeping the genetic diversity high within the population.

Before mating can actually occur the male must first court the female. Courtship in sea turtles entails the nuzzling of heads and the playful biting of the back of the females' neck and rear flippers by the male. If the love bites and nuzzles do not chase the female away, the male will attach himself to the carapace (top shell) of the female using claws that protrude from his front flippers. Copulation (sexual intercourse) occurs once the male wraps his long tail, which only the males have, under the female pressing it against her plastron (bottom shell). This sperm is then stored by the female to be used to fertilize the eggs that she shall lay 2 to 3 years later. Copulation can occur either underwater or at the surface.







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