We went to Mon Repos last November in an attempt to see loggerhead turtles laying on the beach. While the group before us was taken from the Conservation Centre down to the beach to see a turtle, no other turtles had arrived by 9.30pm, when we had to leave.
So in February we made another trip from Brisbane (about four and a half hours). While the laying season was almost over, this time were we lucky enough to see some babies hatching and making their way down to the sea.
This visit was very special for me as I met up with a Flickr friend Ann who came to see the turtles with us.
Mon Repos hosts the largest concentration of nesting marine turtles on the eastern Australian mainland and supports the most significant nesting population of the endangered loggerhead turtle in the South Pacific Ocean region. Successful breeding here is critical if the loggerhead species is to survive.
Young woman riding on the back of a turtle at Mon Repos Beach, near Bundaberg, c 1930. Turtle riding is now illegal, as it could injure the turtles. (Unidentified photographer, public domain picture owned by State Library of Queensland).
We (58 of us) were in Group 1 of the three groups who attended the Conservation Centre that night, and were assembled quite quickly after the centre opened at 7pm, and led down to the beach, with restricted lighting. We were taken to a nest where the baby turtles were beginning to hatch, and this particular nest was being monitored by a research student investigating aspects of multiple paternity in turtles. Apparently female turtles can have a bit of a fling on their way to the nesting beaches, and any single clutch can contain eggs fertilised by up to five fathers.
When we arrived at “our” nest, the hatchlings had dug their way up from a depth of about .5 metre. A piece of cardboard had been placed over them and was removed when we arrived. For about 15 minutes they just lay there in a sleepy little heap, then as they began to stir, they were gathered into a cage to ensure that none of them wandered off the wrong way. About ten of them were taken off to have a small piece of their carapace removed for DNA testing, before being returned to the cage.
While we were waiting for the selected turtles to be returned from their DNA testing, the rangers passed some of the turtles around the group. This was the only time we were able to photograph them, as having other lights on the beach would disorientate the turtles on their way to the sea.
An adult loggerhead is about 92 cm long, and weighs, on average, about 115 kg. The hatchlings are about 4.5 cm long and weigh about 20 grams.
To break open their shells, hatchlings use a temporary, sharp egg-tooth, called a "caruncle," an extension of the upper jaw that falls off soon after birth. Digging out of the nest is a group effort that can take several days.
Hatchlings usually emerge from their nest at night when temperatures are cooler. Once they decide to burst out, they erupt from the nest cavity as a group.
The little turtles orient themselves to the brightest horizon, and then dash toward the sea. This is why lighting is restricted around the rookery, as the turtles can be easily disoriented by artificial lighting.
Once the 10 turtles who had been DNA tested were returned to the holding cage, the turtle rangers supervised their entry into the sea. People from the group were invited to stand in a line with their legs astride (as if we were playing tunnel ball) and shine our torches for the turtles to follow the lights into the sea. The rangers were then able to see any turtles who went in the wrong direction and set them back on course.
I was standing on the end of the line which meant I was in the sea most of the time (bad luck for my shoes and socks) but it meant I had a great view of the turtles entering the water.
Unfortunately, we weren’t able to photograph this event, but it was a truly memorable experience.
Here is a web page which contains a video (taken by some lucky people who had obtained some kind of special permission to film on the beach) of turtles hatching at Mon Repos: http://underwater.com.au/article/id/10131/
Once in the water, hatchlings typically swim several miles off shore, where they are caught in currents and seaweed that may carry them for years before returning to nearshore waters. There are many obstacles for hatchlings in the open ocean. Sharks, big fish and circling birds all eat baby turtles, and they die after accidentally eating tar balls and plastic garbage. The obstacles are so numerous for baby turtles that only about one in 1,000 survives to adulthood.
Mike was the student who was studying aspects of multiple paternity in loggerhead turtles. When the turtles had made their way into the sea, it was his job to dig down into the nest – a very smelly job, apparently - to check if there were any unhatched turtles and to retrieve all the shells for counting. In this particular nest, there were about 10 more turtles who hadn’t left with the others, so they were given a second chance.
Counting the shells was a laborious process, as in Australia the average clutch size is 127 eggs, although this can vary considerably between individual nests. From this nest, about 100 live turtles had made their way into the sea, and about 20 hadn’t hatched (I think).
When the eggs are laid, rangers ensure that an orange tag is buried with the eggs recording information which includes the date of the laying. In the course of his digging, Mike retrieved the orange tag which showed that these eggs had been laid on 27th December, which meant they had taken eight weeks and two days to hatch.
Photo by Richard Ling www.rling.com at www.flickr.com/photos/rling/4965778554/in/pool-1761615@N21/ under Creative Commons licence http://creativecommons.org/licenses/by-nc-sa/2.0/deed.en
Loggerhead turtles generally to not begin breeding until around the age of 30. Sounds like a good deal until you learn that if they survive the many hazards that turtles face today, they can continue laying eggs until 60 years of age. Females can reproduce several times in a single mating season, but then have a spell of between two to five years – understandably.
While Mon Repos beach is closed to the public from 6pm to 6am during the nesting season, it is open during the day. A couple of days later, I took the 2km walk from Bargara Beach, where we were staying, to Mon Repos.
I was delighted to find evidence of where turtles had been hatching – traces of the rubbery egg shells around newly-disturbed sand, just above the high tide mark.
Several of these recently-vacated nests could be seen along the beach, above the high tide mark.
Most females return faithfully to the same beach where they were hatched each time they are ready to nest. Not only do they appear on the same beach, they often emerge within a few hundred yards of where they last nested.
I wonder if the turtle who came out of this shell will be back here in 30 years time. I hope so!