Happy international turtle day! Turtle’s hold a very special place in my heart and are in desperate need for our attention. 6 of the 7 sea turtle species are listed as threatened or endangered, and this is due to a wide range of reasons.
Turtles come in all shapes and sizes and live in both freshwater and the ocean. They are an incredibly important species, providing many ecosystem services, and have been around since the dinosaurs (for more than 100 million years). Without hawksbill turtles (Eretmochelys imbricata), coral reefs would die out, causing complete ecological collapse, as they graze on sponges that would otherwise outgrow the corals, shading them from their necessary source of light. Greens (Chelonia mydas) and leatherbacks (Dermochelys coriacea), grazing habits also provide vital ecosystem management by maintaining seagrass and jellyfish abundance, respectively. The latter of which, has seen an increase in jellyfish numbers due to decreasing turtle populations, which has a knock-on effect on fish numbers, as more jellyfish are consuming larval fish, leaving fewer fish to grow to adulthood. Furthermore, when marine turtles return to shore to nest, they lay 100s of eggs each season. This provides numerous sources of nutrients for the coastal ecosystem as the eggs provide food for predators (still hurts my heart a little, but it’s important) and the shells left behind once the turtles have hatched, are recycled by invertebrates and microorganisms. In turn, this offers nutrients for coastal plants which provide stability and structure for dunes.
Physiologically, they are fascinating! My own research has focused on their astounding ability to remain in the complete absence of oxygen (anoxia) for up to 5 months, without suffering cellular injury. As they are obligate aerobes, just like us, they rely on oxygen for respiration, and so therefore, this feat is the same as us holding our breath for 5 months. This research is important for scientists striving to improve understanding and treatments for stroke and cardiac disease.
Without human interference, turtles have one of the longest lifespans in the animal kingdom, ranging from an estimated 30 to possibly even 400 years (Galapagos tortoise)! Again, highlighting their strikingly amazing physiology.
Additionally, they can navigate 100s of miles of migratory routes to cross oceans and even return to the very beach they hatched on! They do this using the magnetic fields of the Earth, using their internal compass to detect the signposting changes of this field. As this primarily relies on memory, it is of upmost importance that they have enough space upon hatching to imprint on their beaches. This means no picking them up whilst on holiday and placing them into the oceans yourself.
Finally, like most reptiles, turtles have a different process of sex determination, temperature sex determination. This means they have no sex chromosomes that would genetically determine the sex of the offspring, but instead, a particular and specific temperature range determines their gender. This particular temperature, that switches on the specific genes that cause sex, is different for different turtle species and each have a specific range that determines a 1:1 sex ratio (equal numbers of both male and female), called the pivotal temperature. Generally, males are produced at lower temperatures and females at greater temperatures.
This is one of the greatest threats to their existence and is where my current MSc thesis research lies. The current changing and warming climate threatens to entirely feminise populations. Further to this, increasing temperatures threaten their habitat, removing important foraging grounds and even creating adverse weather conditions such as storms. Storms and rising sea level, reduces suitable nesting areas and risks flooding of egg chambers, drowning unborn turtles. Another threat that faces their persistence in the wild is unsustainable human consumption. Many turtles and eggs are killed by poaching for food and income. Despite CITES prohibiting international trade of species under threat, illegal trafficking sadly still exists.
The fishing industry is incredibly damaging to turtles too. Many turtles are killed as bycatch (caught in nets intended for other species) or from boat strikes. What is more horrific, is that many turtles see boats as a source of food, as tourists and fishermen often feed them in harbours- fishermen sell their offcuts to the tourists. However, turtles can’t separate their association from stationary boats in the harbour and when they’re out at sea, often leading to them being killed by propellers.
Lastly, turtles are one of the many unfortunate animals caught in the backlash of plastic misuse. They mistake floating plastic materials for food (jellyfish) and choke which almost always fatal. Also, straws and other plastic debris often gets stuck around them causing injury.
I hope you now find turtles as fascinating as I do and there’s certainly a lot more to be told so watch this space, but for now, visit the links below to find out more.
So, to save turtles, don’t use straws, buy responsibly sourced fish (pole and line caught) or better still none at all, and encourage #systemchangenotclimatechange. #savetheturles #saveouroceans #saynotoplastic #noplanetb
https://www.mcsuk.org/news/solo-beach-trips (Another handy lockdown activity: socially distanced fun things to do that help keep our beaches healthy)
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