Today, we celebrate the ‘World turtle day’, an event that tries
to call the attention and improve the general knowledge about turtles, respect
about their existence and their habitat and to try to create some measures and
guidelines to slow down the quick decrease of their populations and the
possible extinction of species.
This animal has been on earth for more than
200 million years, however, they are disappearing very fast as a result of the
exotic food industry, their habitat destruction and pet commerce, in fact, they
use to travel around 100 years ago in great numbers, too many to count.
Sea turtles are wonderful animals that
spend their whole life traveling being truly oceanic travelers, females always
come back to the exact beach where they were born while males never come back
to land.
Sea turtles are reptiles that have adapted
their live to ocean, so despite the fact that they are turtles they have some
differences with land turtles or tortoises:
-Their lungs are very effective, being able
to hold the air around a maximum of 10 minutes
-The can’t hide their head inside their
shell, the shell consists of carapace (upper portion) and plastron (lower
portion)
-The have flippers instead of legs
-They have no teeth, but they have very
strong beaks like jaws
-They have very good vision in water and an
excellent sense of smell
-They don’t have external ears but have skin
covered eardrums that in fact are very efficient
-They only come to land to lay their eggs (males almost never return
to land) and they move with certain difficulty as their flippers are perfectly
adapted to marine environment
Other reptiles
that readapted to the live in the ocean:
Saltwater crocodile
Sea snake
Marine iguana
As any other reptile they love to spend
time in the surface of the ocean, especially in calm sunny days getting warm
and heating their body and blood or just resting, they fill their lungs with so
many air that their shell stays totally out of the water, resting sleepy
floating like a pineapple in the ocean. This because they are ectotherm,
meaning they regulate their body temperature with the temperature outside.
In the world 7 species of sea turtle exist, out of those seven, five had
been registered in the Azores, being the most common one and the one we usually
see, the loggerhead turtle and the leatherback turtle.
Today let’s learn a bit about a very special one for us:
The
loggerhead turtle (Caretta caretta)
Caretta caretta (the name comes from their large head if compared
with the body size), also known as loggerhead, is the most observed species
during our whale watching tours and can be found around the world. Masirah
Island off the coast of Oman and Florida in the USA have the largest nesting
colonies of loggerheads both receiving tens of thousands of nests per year,
many different populations of loggerhead turtles exists in the world as the
ones of Australia and South Africa that are also relatively big, in Azores we
mainly ‘receive’ individuals form the Caribbean and USA.
The weight of an adult loggerhead is 113 to 140 kg and its carapace
measures from 70 to 124 cm (when adult)
The carapace is heart shaped and has five pairs of costal scutes, a way
to distinguish from other species of sea turtles that have only four pairs.
Each of their flippers has two claws.
The coloration of the carapace varies depending on the amount and type
of organisms that they have adhered to the shell, normally is reddish brown but
if it colorizes with algae it takes a greenish color.
Loggerhead
turtles laying in the surface
Where
are this turtle coming from?
Despite 5 species of sea turtles
occurs in the Azores none of them reproduce in our waters, so where are they
coming from?
This has been a controversial
issue as the closest nesting areas are in the Atlantic coast of Morocco up to
the parallel 35ºN, as the turtle hatchlings couldn’t swim against the strong
currents, the other edge of the Atlantic seems too far away but… that is what
really happens!
These turtles are born in the Caribbean Sea and Unite States where
they head quickly to the open sea before they get predated, they will live
associated to floating objects. Hatchlings spread in many directions, some of
them will use the gulf stream that will lead them to the Azores. From the gulf
stream they will catch the Canary current passing through Madeira and Canary
Islands, eventually they will return to their bird beaches using the North
equatorial stream.
They spend in the Azores what is called ‘the lost years’ where they get
mature between the 15-30 years old, being Madeira and Azores the nursery area
for this big population of the North Atlantic. After that, they stay around
living in shallow waters.
This is
the migration of the loggerhead turtle in the North Atlantic population:
This are the main three age clases we
see in the Azorean waters!
The loggerhead turtle journey:
A loggerhead's journey through life spans tens of thousands of miles
around entire oceans and stars when the female leaves the ocean to nest in the
beach where it was born (1).
Nest is average 115 eggs and incubate under sand for 50–60 days.
Warmer sands produce mostly female turtles and cooler sands result in mostly
males.
A few days after they hatch, the hatchlings emerge together from the
nest at night, scramble quickly to the sea, and are dispersed by ocean currents
(2). Juveniles live near surface of deep ocean waters and are carried by the
current (3).
When sub adult size, turtles swim into nearshore waters (4). Adults
mate along migration routes between foraging and nesting areas (5). Every 2-4
years, adult’s females migrate to the beach where they hatched and make about
3-6 nest at two weeks period (6)
How can
they find their way back to their natal beach?
The theory is that they are able to detect the intensity and angle of
the earth magnetic fields with their brain!
The loggerhead turtle is primarily carnivorous, feeding on crustaceans,
mollusk, sponges, jellyfish and sometime algae. Their powerful jaws are well
suited for eating hard-shelled food. In the Azores have been observed feeding
mainly on jellyfish and crabs.
Natural predators: Natural predators that may find in our waters are
orcas and large sharks.
An adult male of orca feeding on a loggerhead
turtle, photographed in one of our tours
Threats to the loggerhead
turtles in Azores:
Loggerhead turtles are considered as an endangered species, the threats
they face are very numerous, both in land and in the sea, despite they spend
the majority of their live in the sea they need sandy beaches to reproduce and
the small hatchling are very vulnerable.
In the ocean the threats they face are also numerous:
- Plastics and ghosts nest can both trap and suffocate them.
- As a main part of their diet consist on jellyfish the can ‘mistake’
them with plastic bags and shallow them and starve to death.
- As the lay on the surface of the ocean they can hit by boats, killing
or injuring them.
- They very often get trapped in the fishing lines.
A
loggerhead injuried in the back by a boat
As you see the survivals for loggerhead is not easy, the Azores become a
very important nursery area for one of the biggest populations in the world. We
must be careful and protect this wonderful animal.
Happy world turtle day everybody!
