The Cape Verdean national military offers its support to SOS Tartarugas and patrols the beaches at night to protect the nesting turtles from poachers. This means that during nightly patrols you sometimes meet a military fireteam on the beach. Most often, the unit will just stay in one spot and stay there throughout the night. Other times they will patrol with you in the hope of seeing turtles. And occasionally they show a real interest in your work and want to help.
One night I found a turtle nest that had to be relocated. Unfortunately I had just missed the nesting turtle so I did not see her. I started to dig for the eggs and this raised the curiosity of two military soldiers that were nearby. They watched me dig with interest and when I started to extract the eggs from the egg chamber they looked very surprised and left in haste only to come back moments later armed with their AK-47 assault riffles. They seemed to take the protection of the turtle eggs very seriously and stood sentinel over me!
When I was done removing the eggs from the nest I carried them down the beach to a good location to rebury them. Both soldiers followed me, guarding me and the turtle eggs. I had my own personal military escort! When I was done relocating the eggs they both saluted me and marched off. I then carried on with my patrol. It makes me very happy to know that some people take the preservation of their natural heritage very seriously.
Every once in a while you see an adult sea turtle with missing limbs. This can be due to several reasons: it may be that the turtle had a close encounter with a shark; it may be that a motorboat inadvertently struck the turtle; or it may be that the turtle was born with a missing limb.
Last night I saw such a turtle. I was patrolling a beach on the east coast of the island when I came across an interesting asymmetrical turtle track. I carefully followed the track and found a turtle that was missing a back flipper. She was trying to dig an egg chamber to lay her eggs.
What is very curious is that the turtle still went through all of the regular nesting motions and seemed completely oblivious to the fact that she had a missing flipper. She dug with her flipper, scooped some sand up, removed it from the nest cavity, and then shifted her body to dig with her missing flipper. Of course she could not dig with her missing flipper but still went through the ghost motions before shifting her body again and digging with her flipper. After several minutes the turtle decided to give up on this egg chamber as she judged it was not going well enough.
Luckily, the turtle decided to try to dig a new nest further up the beach. I discretely followed her and opted to help her out this time: as the turtle was digging, every time she shifted her body and tried to dig with her missing limb, I would reach in the nest cavity and scoop out some sand for her. Together we built a nice egg chamber and the turtle seemed pleased as she resolved to lay her eggs! She lay close to 80 eggs that all fit nicely in our egg chamber. After covering up her nest and camouflaging the nesting area, I watched her return to the sea. Due to her missing limb, she walked a little bit sideways like a crab.
This particular turtle had been tagged earlier this season and was spotted nesting twice already. I imagine that the other rangers that saw her nest also gave her a helping hand when she was digging!
The day after a nest hatches, nest excavations are carried out. This is done for two main reasons:
- it allows hatchlings that were unable to make it out of the nest on their own to be released
- it enables the calculation of the success rate of each nest
Not all eggs develop into fully formed live hatchlings. Sometimes eggs are infertile, sometimes eggs fail during development, and sometimes hatchlings suffocate at the bottom of the nest. This happens for nests in the hatchery and for nests incubating naturally on the beach. The success rate of a nest is given as the number of live hatchings out of the nest against the total number of eggs in the nest.
Quantifying the success rate of a nest can be very informative scientifically. As part of my research I am trying to see if there is a relationship between the success rate of a nest and environmental variables such as sand temperature and rainfall.
As well as being scientifically informative, a nest excavation is also an exciting time and attracts many tourists because of the live hatchlings that are excavated from the nests. The opportunity to see wild baby sea turtles is unique. They are quite an amazing sight!
Hatchlings usually wait for nighttime to emerge from the sand. The temperatures are cooler and they can reach the sea under the cover of darkness. Something quite unique happened yesterday at the hatchery: a nest emerged in the late afternoon!
First a hatchling popped his head out of the sand. Then a flipper. Then another hatchling showed his face. And another. And before you know it, dozens of little hatchlings were crawling out of the sand! It was very special to see.
The hatchlings were full of energy and scattered around the hatchery. We collected them, counted them carefully, and released them altogether afterwards. It is quite rare to see this happen during the day so everyone present felt very lucky!
Turtle nests are sometimes relocated to the hatchery. The hatchery is a place where the eggs are kept safe from predators and where they can incubate naturally. It is a pretty unique place, in that when you are walking around the hatchery you know that there are literally thousands of turtle eggs developing into hatchlings just under your feet!
Each nest is carefully labelled and the due date is recorded. Several days before the nest is due to hatch a circular cage is placed atop the nest so that when the hatchlings emerge from the sand they do not scatter everywhere. During the night, a ranger will check the nests every hour so that he can immediately release any hatchling that emerge from the sand. The hatchlings are brought to the top of a beach and are released. They then reach the sea on their own.
Sleeping in the hatchery and releasing the hatchlings is something that I have not yet done. Hopefully I can do this before the end of my stay!
Relocating sea turtle nests from one site to another is a common conservation practice. The rationale behind this measure is that some nests would be “doomed” if they were left where there were laid.
I already relocated several nests this year and want to share with you the entire process, from locating the egg chamber, to burying the eggs at another site.
When I find a turtle nest that needs to be relocated, the first thing I need to do is to locate the turtle eggs. In order to do this, I use an Egg Chamber Locator, which is basically a stick but scientists often like to give fancy names to common things. I use the ECL to poke at the sand and try to locate a soft spot within the nesting area. This soft spot is the place where the turtle dug her nest, laid her eggs, and subsequently covered it with sand. It is a common misconception that the stick is used to try to poke an egg to find the nest. The pokes are gentle and are only used to assess the compactness of the sand.
Once the egg chamber is located, I cautiously dig down to the eggs. When I find the first egg, I carefully start transferring the eggs to a Mobile Egg Transporter (a bucket). The eggs are transferred one by one and the polarity of each egg is preserved: eggs are carefully transferred so that “North” always faces “North” and “South” always “South”. All the eggs are removed in this manner. Once the egg chamber is emptied, I take the measurements of the nest: depth of the nest, width at the bottom, and width at the top. I finish by covering the eggs with a cloth to keep them in the cool and place some sand from the original nest atop them.
The eggs are then moved to another location on the beach or to the hatchery. At the new site, I start by digging a new egg chamber that has the same dimensions as the original nest. I dig a light bulb-shaped hole and carefully measure all the dimensions to ensure all the eggs will fit in the nest! I then place the eggs in the new egg chamber. Again, I ensure that polarity is maintained. All the eggs are placed and then I cover them with sand. First I use the sand that I removed from the original site, then I use the sand from the hole I dug at the new site.
Finally I can place a nest marker where the eggs have been moved. In approximately 60 days I can come back to see that the eggs have hatched and the hatchlings make it safely to the sea!
When a turtle comes ashore to nest, she first scans the beach for a good spot to nest. Occasionally, she will turn around and go back to the sea without laying her eggs. These events are called false crawls and occur if the turtle does not find a spot she likes or if she is disturbed in the process of nesting.
When the turtle does nest, it does not always mean that she chose a good nesting spot: she may have laid her eggs in a place where they are at risk. To improve the chances of survival of such nests, we choose to move these nests either to a safer place on the beach, either to a hatchery. Here in Sal, there are four main reasons to relocate a nest:
- Predators: if the nest is laid in an area where there are many ghost crabs and/or stray dogs it is at risk of being predated upon.
- Vegetation: if the nest is too close to dune vegetation it is at risk of being destroyed by the roots of the plants.
- Water: if the nest is too close to the sea it is at risk of being drowned at high tide.
- Photopollution: if the nest is laid in a beach where there are many artificial lights, there is a risk that the emerging hatchlings will not find the sea as they are attracted to the lights (see section 2. of “Conservation”).
A turtle nest that has to be relocated because of light pollution
As an ecologist I would much prefer not having to interfere with the natural cycle of things. But as marine turtles are endangered, such conservation measures may be crucial to the survival of the species. The estimated survival rate of a hatchling to adulthood is about one in a thousand, so it is vital to protect as many nests as possible.