Floogle facts: Turtles
Written by Frankie Paterson
Loggerhead turtles inhabit subtropical and temperate areas of ocean. Its range includes the Atlantic, Pacific, Indian Oceans and the Mediterranean Sea. This reptile is a migratory species and every 2.5 years (approx.) females and males will journey from feeding grounds to nesting sites and back again. They can swim anywhere between 20-40 km/day but can move faster in the Gulf Stream and can achieve 80 km/day. Populations found in the Mediterranean can travel the breadth of the sea from Turkey to Morocco; around 3000 km.
2) LOGGERHEAD TURTLES THREATS
There are several major threats to wild populations of loggerhead turtles. They include;
- By-catch by fisherman (accidental removal)
- Harvested (direct removal)
- Coastal developments
- Pollution and pathogens
- Climate change
Bycatch is one of the most high-level risks to populations. If fishing areas surround foraging and nesting sites of the loggerhead turtle, fatalities will continue to increase. Organisations like the IUCN and WAZA have created information packs on “safe nets” and sustainable fishing although this information has not necessarily reached the fishermen themselves.
Here is a good journal explaining how climate change is affecting loggerhead populations (Hawkes et al, 2014). http://www.seaturtle.org/PDF/HawkesLA_2014_InCoastalConservation_p287-310.pdf
3) LOGGERHEAD TURTLE – UNDERWATER BEHAVIOUR
Here a great video that shows the underwater lives of loggerhead turtles!
It is an incredible insight and explains the natural behaviours loggerheads present in the wild. These then make up the species specific behavioural repertoire. Research done can help both aspects of integrated conservation (in-situ & ex-situ). Our projects in Greece support the protection of this species.
4) LOGGERHEAD TURTLE – ADAPTATIONS
Turtles are highly adapted to life in the oceans. One of the most important adaptations is being able to dive to great depths to forage on the ocean floor whilst conserving as much energy as possible. These dives can last from 4 to 5 minutes at which time they surface for 1 to 3 seconds, some have been recorded to dive as many as 500 times every 12 hours. So how do they do it?
Many marine animals have evolved buoyancy aids or regulating organs to stabilise their position in the water without expending energy. The function of the organ is specially adapted to increase survivability and allows species to fill a specific ecological niche. Sea turtles including loggerheads often rest for extended periods at the same depth, so this adaptation is advantageous.
Chelonian sea turtles which include the loggerhead species, use their lungs as a buoyancy organ as well as a major oxygen store when diving. When air-breathing species dive air is enclosed in the respiratory system. For this reason, they are buoyant at the surface and have to overcome this buoyancy by forcefully swimming during the first phase of the descent. As depth increases, the air becomes compressed meaning buoyancy is reduced. This will occur until neutral buoyancy occurs i.e when an animal’s body density is higher than that of the surrounding water. Beyond this depth, the animal will sink!
When the oxygen in their lungs reaches a critical level they ascend to take a breath. This can be a tricky matter as, like humans, turtles can suffer from decompression sickness or ‘the bends’, so again being able to stay consistently buoyant is advantageous and much like human divers their ascent is slow and calculated.
A study has shown that turtles caught in trawler nets are more likely to be killed by the bends due to the rapid ascent of the net. This is now considered a leading factor in turtle mortality associated with bycatch.
Want to find out more? Check out the links below!
The dual function of the lung in chelonian sea turtles: buoyancy control and oxygen storage
5) LOGGERHEAD TURTLE FEEDING AND NUTRITION
Here is a good journal on ‘The feeding habit of sea turtles influences their reaction to artificial marine debris’. It looks into the prevalence of turtles eating plastic debris and other waste products produced by humans. Turtles seem to confuse drifting debris with food. Omnivorous green turtles were more attracted by artificial debris but the jellyfish-eating loggerhead is also at risk. Loggerheads are primarily carnivorous.
Juveniles, sub-adults and adults feed upon clams, horseshoe crabs, jellyfish, pteropods, squid and flying fish but hatchlings often eat sponges, jellyfishes, Sargassum weeds, small gastropods and crustaceans.
Scientific Reports 6, Article number: 28015 (2016). doi:10.1038
6) LOGGERHEAD TURTLE – EVOLUTION
Sea turtles, the Chelonioidea (Cryptodira), have been around since the Early Cretaceous or the Late Jurassic. At this time they were one of the main group of modern marine reptiles. Their highest diversity occurred during the Late Cretaceous – Early Palaeogene interval. This family was full of diverse ecological adaptations to an aquatic life. A recent study looked at a species that had a long protruding sucker-like mouth more closely resembling an echidna snout.
So it just goes to show there is more in the oceans than meets the eye. Having only investigated 5% of the oceans of the planet what else is still there to be discovered!?!
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