Sea turtles of Cabo Vere

Our original plan was to come to Cabo Verde to participate in an internship for Turtle Foundation. We wanted to gain more experience in the field and learn as much as possible. It has been an incredible experience but living in a remote location for a long time was a challenge at times!


Our aim was to raise the awareness about sea turtles and especially of the loggerhead species which is the only species that nest in Cabo Verde (other species of sea turtles rarely nest here). Furthermore, the archipelago is also the third most important nesting site for this species in the world!



All species of marine turtles have different track patterns and they can serve as a tool for their identification.


It is important to establish which track is emerging and which one returning.  In loggerheads, the track has a 'comma' shape with asymmetrical diagonal marks and it is about 70-90 cm wide. Turtle track will lead to a nest if a crawl is complete.If a nest is present there will be an evidence of a pit and a covering and sand is 'thrown' on the emerging track. In that case a GPS coordinate of a nest is taken and written in a notebook. The track is crossed by foot if seen in the night and S shape is drawn over the track if seen in the morning during  censo (morning patrol).


The stages of nesting are as follow:


1. Emerging from the sea

2. Finding a location for a nest

3. Making a body pit

4. Digging a chamber

5. Depositing eggs

6. Covering eggs and nest

7. Camouflaging nest

8. Returning to the sea


Nesting can take anything between 1-2 or more hours depending on a turtle and conditions (f.e. a turtle can get disorientated by light pollution on the beach).


An attempt means that a turtle made a body pit, started to dig but abandoned the place. This can happen for various reasons most likely due to human factor or beach condition.


Turtles are very sensitive to disturbance and when this happens for example by humans they can abandon nesting and crawl back to sea. False crawl has normally an U shape and a turtle crawls up and down the beach without digging. If she starts to dig but doesn't lay eggs than in scientific literature this is called an attempt. Sometimes there is an egg chamber but with no eggs and in that case we talk about abandoned egg chamber. In some cases a turtle can make numerous attempts but still doesn't nest or nest after several attempts.


Some biologist have slightly different classification depending on a their protocols but one thing is in common- an attempt means that a turtle hasn't disposed eggs. Therefore it is massively important to make sure that the factors of disturbance are minimized especially when on a guided tour. One should not approach a turtle without the guidance of a licensed tour operator. If a turtle doesn't nest then she have to find a different location and this might be in less protected area where she could be threatened by poachers (there is still a high number of poachers on some beaches in Boavista).




In loggerhead turtles it takes about 60 days for a hatchling to hatch and the temperature  of a nest will affect the sex of it  (incubation temperature range is between 26-32 °C). Cooler temperatures produce more males and higher temperatures produce more females. The term pivotal temperature is used when there is an equal ratio of both females and males (30 °C ).

We had to count hatchlings from each nest (sometimes more than 120) and measure their length and width and weigh them (only from a representative sample) before setting them free! Once on the beach, about 5 meters from water, we tilted the bucket and made sure that no ghost crab got them! Quite a challenge as crabs were fast and hungry!


Have you ever wondered what conservationists have to take with them on their night patrol? What sort of equipment is needed in order to perform a scientific based research of the sea turtle in the field?

First, it is necessary to check if everything is in the bag and in proper working order before the night patrol begins. There are few smaller bags within a rucksack to make it easier for a leader to select the right material. One of the most important things is to document everything you do with a turtle or when you encounter a turtle. There are two notebooks for it. One is to write a general information (like a time of encounter, GPS coordinates, high or low tide, if it was a false crawl  or a nest). The other notebook goes more into a detail about nesting (phases of nesting, time, location of a nest, number of metal tags and a PIT tag, measurements).


Then, there are paired metal tags and pliers in a bag. Metal tags are put on a second (biggest) scale on a front flipper (they have letters and numbers on them). The area has to be cleaned with alcohol first. PIT tag is a microchip in a top of a needle which is applied with a syringe under the second scale of a right flipper. It has its unique number. It has to be scanned first to make sure it's working. It is against a good practice to start  putting tags on a turtle before she is covering. Only when she has finished laying the eggs and started covering then it is time to start with measurements and other tasks.

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Conservationists have to also measure the length and width of a turtle with a tape (3 times). In some cases, DNA sample might be needed and from the base of a scale of a front flipper a tiny sample is taken with a scalpel. Parasite sample is obtained from a cloaca if some worms are present and they are taken with tweezers into a tube. All this has to be properly documented. Turtle has to be also checked for barnacles and general health (if some part is missing it has to be documented). Indeed, a lot has to be done in a short span of time (ideally when she is still covering) but the wellbeing of a turtle comes first !


Once hatchlings have hatched, eggs shells remain scattered in the nest and in some cases also some unhatched eggs. It is rare to have a 100 percent success rate (all eggs hatched) and methods like excavations are used to see what happened in a turtle nest. 

First, one has to get to the nest which is not always easy! Even if you know the location, it happens that nest has shifted a little an it can take some time to find it and in some cases it's never found!


Hatchlings that have hatched leave behind an egg shell  (shown in above picture except the top right corner where are unhatched eggs).


Unhatched eggs have to be opened (it can be quite smelly!) and if possible a stage of embryo development is established and documented. There are many reasons why eggs didn't hatched- bacteria, contamination by roots of plants or predation (main predator of hatchlings in Cabo Verde is a ghost crab that preys on eggs and also live hatchlings). In later stages of development hatchlings can suffocate (they must breathe air during pipping).

In some cases, live hatchlings are found in a nest, some of them might have some deformities and their survival will be unfortunately  unlikely. But the others might be more lucky and hopefully will make it!

Recommended reading:

Our Sea Turtles: A Practical Guide to the Atlantic and Gulf from Canada to Mexico.



If you would like to learn more about sea turtles then don't look further, this colourful guidebook has it all! It provides a clear overview of sea turtle biology (including behaviour and turtle tracks) and why it is crucial that we protect them