– Writing –
– Fighting for Survival: The Sea Turtles of Kefalonia –
It is late August in Argostoli on the Greek island of Kefalonia. Peak holiday season is in full swing and walking along the harbourside there is a buzz in the air. Crowds of tourists are gathered along the waters edge and dozens of fishing vessels are moored alongside the harbour, attempting to entice the onlookers to the day’s catch. Upon closer inspection, it is not the fish the tourists are interested in, but rather the creatures that are swimming alongside the boats in the azure blue waters of the Mediterranean.
As a large, red-brown carapace glides into view, it is clear that the tourists’ attention is focused on one of the island’s majestic prehistoric inhabitants, an adult Loggerhead sea turtle.
The turtles glide gracefully through the water, stopping only to feed on barnacles clinging to the harbour wall, or the discarded catch from fishermen.
I am amazed by their size; on average 100cm in length and weighing more than 135kg, they far outweigh most humans. It is an astonishing transformation from the small vulnerable hatchlings that fit in the palm of a hand.
Loggerheads are the world’s third largest turtles, after the soft shelled Leatherbacks and the hard shelled Green turtles. They are characterised by their uniquely large head and reddish brown shell and are omnivorous, feeding primarily on bottom dwelling invertebrates.
Loggerhead turtles have been a feature of the world’s ecosystems for the last 40 million years, and although their range covers all but the most hostile of the world’s oceans, they are now on the IUCN list of vulnerable species. The natural obstacles faced by young and adult sea turtles are staggering, but it is the increased threat from humans that is driving the species to extinction.
This is the story of the sea turtles of Kefalonia, of their epic journey from egg to adult, a journey only the fittest and luckiest individuals will survive and return to Kefalonia to lay eggs of their own.
These adults in the harbour are the lucky few. Only an estimated 1 in 10,000 hatchlings survive all the challenges to reach this stage.
I travelled to Kefalonia to document the challenges Loggerhead turtles face on their journey from egg to adulthood, and find out how conservation organisations are working to save the species from extinction. I joined the organisation Wildlife Sense as they carried out vital research, monitoring the local turtle populations in an attempt to preserve one of the last remaining Loggerhead strongholds.
The first stage in the life of a Loggerhead sea turtle occurs when the female ventures from the sea and climbs the beach in search of a suitable location to lay eggs. Our first task was to survey the beaches for any evidence of nesting.
Rising at 5am each morning with the stars still shining and the sun below the horizon, I joined other volunteers as we cycled for over an hour to reach the nesting beaches. We walked along the beaches, looking for any evidence of new emergences before tracks were washed away by the incoming tide.
A fascinating characteristic of sea turtles is that they almost always return to the same area of birth, and commonly the same beach, to lay eggs of their own. Females emerge from the sea under the cover of darkness to build a nest. This is the only time an adult will leave the sea during its whole life cycle, up to 70 years.
If a female emerges and decides a beach is unsuitable, she will not lay eggs and return to the ocean. Nikos Vallianos, project leader at Wildlife Sense, explained “These types of non nesting emergences are becoming increasingly common due to factors such as tourist disturbance and light pollution from hotels and beach bars”.
Morning surveys also included checking known nests for any evidence of hatching. By counting tracks and monitoring nests each day, valuble data can be collected. Nests contain on average 100 eggs and incubate for 50-60 days. As researchers know when each nest was laid, they can estimate when each nest will hatch. If a nest is 10 days overdue, at the 70 day mark, it is considered non viable, and must be excavated to find the cause of their demise.
This was the next task for the Wildlife Sense team. There are many reasons why a nest may not hatch. Disturbance by tourists, predators and the sea could be responsible, as could bacterial / fungal infection.
On our hands and knees, we dug down to find the nest, often buried over 30cm below the surface, creating a crater like hole on the beach in the process. As we dug down we came across a large rock. Our fear was the rock may have blocked the exit from the nest below. As we removed the rock, sure enough we caught our first glimpse of the nest, and the palm sized outline of a hatchling. It was motionless, and upon closer inspection had clearly been dead for some time.
We dug on, encouraged by the thought there may still be live hatchlings in the nest below. Moments later, our efforts were rewarded with movement from two live hatchlings stuck beneath the rock. We carefully proceeded to lift them up and place them in the trench we had dug towards the ocean. The first stage of a hatchlings life requires a weary scurry towards the sea, warming muscles up before battling the elements of the ocean.
Unfortunately these were the only remaining live individuals and we set about cracking open the unhatched eggs to investigate the reason for their failure to hatch.
It appeared bacterial and fungal infections had overcome a number of eggs, specifically from the microbe S. marcescens, which is characterised by an almost fluorescent pink colouring to the yolk. These turtles had fallen at the first stage of their epic journey.
The next day brought more drama. During the routine morning beach survey we found that the storm the previous night had caused the tide to rise, flooding a number of nests. With no intervention the wet eggs would rot, so it was a race against time to relocate the flooded nests. We delicately moved the eggs one by one to more suitable nest locations further up the beach where they could develop as normal. For one nest it was too late, and the tide had risen too high. The eggs had started to rot, turning a dark shade of green as a result of hours submerged in a lake of saltwater.
Without the work of volunteers around the Argostoli area, four nests would have been lost to the storm that night.
If eggs are successful in hatching, the young turtles will encounter a new set of challenges in their first stage of life, on their journey from nest to sea.
Light pollution is a significant problem for hatchlings. Through millions of years of evolution turtles have adapted to hatch at night, when the sand is coolest, and follow the brightest light, historically being towards the sea due to the reflection of the night sky in the water. Because of an increase in light from beach bars, hotels and cafes, hatchlings have trouble determining which direction to head in. Hatchlings are attracted to these bright lights rather than the ocean and once the sun rises and temperatures climb, the newborns are at significant risk of dehydration.
To combat this problem, dedicated volunteers from Wildlife Sense spend nights on the beaches most affected by light pollution. Boxes are placed over the nests to prevent hatchlings heading towards artificial lights.Volunteers regularly check the boxes and place any hatchlings in a trench to begin their journey towards the sea. After following tracks to find a disorientated hatchling heading away from sea towards the bright lights of the beach bar I held the 20g baby in the palm of my hand. It is remarkable that in 20 years these babies may return to Argostoli harbour weighing more than most humans.
Once the hatchlings disappear beyond the waves the real struggle for survival begins. A tiny speck in a vast ocean, young turtles are prey for a number of oceanic predators, including crabs, sharks and whales.
It will be at least 17 years until the females return to land to lay eggs. Hatchlings swim for 20 hours until they are far out to sea, where they live using the macroalgae Sargassum for protection. They will remain here, growing until they are 45cm in length, when they will then migrate to inshore waters using a combination of magnetic and visual cues to direct themselves.
Returning to inshore waters, adult turtles again face a range of threats from contact with humans.
Although poaching is not a problem in Europe, in central America turtles are seriously threatened by hunting for their eggs and meat, which are considered a delicacy in many places.
In Europe the primary threat to adult turtles is entanglement in fishing gear including longlines and gill nets. Loggerheads need to breath air at least every seven hours, so getting entangled can often have lethal consequences.
It is worrying that the harbour turtles of Argostoli are in such close proximity to fishing vessels and the associated dangers they present. The slow moving giants are often unable to react to fast boats, and collisions are a common occurrence.
In addition to the commercial fishing vessels in the harbour, local people often fish with hooks and lines from the harbour wall. Although illegal, the harbour authorities do little to enforce the law, despite the volunteers best efforts for cooperation.
Plastics also pose a threat to sea turtles, as they are often mistaken for food items. Floating in the water, plastic bags are easily mistaken for the jellyfish that make up a large part of the sea turtle diet,. Ingested plastic can lead to a slow and painful death, from intestinal blockage, reduced nutrient absorption and malnutrition, suffocation, ulcerations, or starvation.
Scientists have also discovered Ingested plastics release toxic compounds, including polychlorinated biphenyls, which may accumulate in internal tissues. Such toxins can lead to a thinning of eggshells, tissue damage, or deviation from natural behaviours.
There were worrying levels of plastic debris found every morning on the beach surveys in areas yards from nests, and numerous items floating in the harbour, tempting the turtles to a fatal meal.
In addition to numerous local challenges the turtles of Kefalonia face, they are also threatened on a global scale. Scientists are currently researching how climate change may impact loggerhead populations in the future. An intriguing feature of turtle offspring is that the sex of offspring is determined by the ambient temperature of the nest. An incubation temperature of 3 degrees celsius results in an even sex ratio. If the temperature is lower, more males will be born, and if higher, more females will develop. As global temperatures increase scientists predict sex ratios will skew and the number of females will increase.
With a seemingly endless series of challenges facing the turtles, it is easy to believe that Loggerhead populations in Kefalonia face a dreary and uncertain future. However, there is hope. Commitment from conservation organisations, volunteers and local communities appears to be growing and valuable data is being gathered. Nests are being protected and local communities and businesses are engaging in the conservation effort by switching off beach bar lights and reducing pollution. Fishermen are using more sustainable methods, with the introduction of turtle excluder devices in nets enabling turtles to escape if caught in gill nets.
For the species to survive in the long term cooperation between conservationists, fishermen and the tourist industry is key. Fishermen and their equipment are the primary cause of non-natural adult deaths, and many nesting beaches are shared with tourists and beach bars. If these groups can work together then there are at least a few less challenges for the sea turtles on their journey through life and one day, maybe the lost hatchling I held in my palm will return to the island to lay its own nest.