Big Softy

Thursday, October 31, 2024

Big Softy

Today’s special animal friend is the leatherback sea turtle, Dermochelys coriacea, the world’s largest turtle and heaviest non-crocodilian reptile.  This immense animal can be 8’10” long and weigh 1,100 lbs. It is the only species in its family, the Dermochelyidae, a name which identifies its distinctive characteristic, “skin shell.”  Unlike the rest of the turtles and tortoises, the leatherback does not have a hard, bony carapace. Instead, its back is made of oily flesh covered by thick, leathery skin reinforced with small, bony particles called osteoderms.

The leatherback’s body is the most “hydrodynamic” of any turtle.  For propulsion, they have enormous, flat front flippers that can be over 8 feet long. Their rear flippers are much smaller and are used as a rudder.  None of the flippers has claws or nails.  Although reptiles are typically “cold-blooded” or exothermic, leatherback sea turtles generate heat internally:  not through metabolic processes, like mammals, but through almost constant activity, spending less than 1% of the day at rest.  They can survive water temperatures below 40 degrees F.

Although they usually swim rather slowly, they have been clocked at over 20 mph, and they can dive as deep as 4,100 feet.  Dives lasting up to an hour have been observed, but less than ten minutes underwater is typical.  Instead of teeth, they have small, sharp projections around their mouth and pointing down their esophagus.  This allows them to eat gelatinous sea animals such as jellyfish and salps (“sea squirts”), which are weird.

Australian Museum explains salps..

They are the most widely distributed of all sea turtles, with individuals migrating up to 10,000 miles from their hatching location.  Leatherback females nest every 2 to 3 years.  They do not always return to their natal beach, but they usually nest in the part of the world where they hatched.  During a nesting season, a female will lay 4 to 7 clutches, each containing 80 or more pool-ball sized fertilized eggs and about 30 smaller, unfertilized eggs.  

The fertilized eggs hatch in about 2 months.

Surviving hatchlings mature in 9 to 20 years.  Scientists aren’t really sure.  And they can live “40 or 50 years or more.”  The leatherback sea turtle is rated Vulnerable by IUCN.  It is estimated that there are 26,000 to 40,000 nesting females.  Pollution, especially plastic bags that the turtles swallow, thinking they are jellyfish, is a danger.  “Bycatch” in fishing equipment is a more significant threat.  The turtles are protected in many countries, but adults and eggs are collected for food in others.  And finally, coastal development reduces the availability of nesting sites.