Sending out an S.O.S to the world!

“It is not the strongest of the species that survives, it is not the most intelligent that survives, it is the one that is most adaptable to change”

-Charles Darwin

None can be more accurate when it comes to the survival of marine turtles. From the moment the eggs are laid the battle for survival begins, but what, or rather who, is their main enemy? Dun dun daaaaaa! Not to be melodramatic but yes we do play a major role  in the survival of these species.

Let us just recap on the last blog about the biology of sea turtles. We learnt that they are widely dispersed migratory organisms that cover large distances between their foraging grounds and their natal nesting beaches. Because turtles cross geographical, political  and cultural boundaries, they are hard to monitor especially when different countries may or may not have national laws to protect them. There are 5 major anthropogenic threats that have contributed to declining marine turtle populations: fisheries impacts, direct take, coastal development, climate change and predation. So let us take a closer look.

Fisheries impacts

Fishing activities are thought to be the greatest cause of marine turtle decline. Trawls, longlines, driftnets, gillnets, pots, traps and discarded fishing line all play a role in incidental capture or entanglement. It is estimated that each year 250,000 loggerhead turtles are caught globally in longline fishery operations and 80% of live turtles released still have hooks inside their months, often leading to delayed mortality. Loss of fishing gear such as nets can also cause ghost fishing (entanglement of wildlife in lost fishing gear). Up to 30km of net can be lost from a single deep drift fishing fleet, resulting in disastrous consequences. Here in the Cayman Islands our main fishing impact is entanglement in discarded fishing line or fish hook injuries (http://www.cayman27.com.ky/2014/10/29/drowned-turtle-found-tangled-in-fishing-line-near-fish-pot) and when they leave Caymanian waters our turtles are also exposed to all the pressures of global large scale industrialised fisheries.

Direct take

The second biggest threat is through direct taking and harvesting of adults, juveniles and eggs, which has been going on for centuries, as a food resource as well as for international trade in turtle products such as shells. Between 1688 and 1730, based on fishery records, the estimated population size of green turtles in the Caribbean was 6.5 million. However, by the early 1800s turtle fishermen had exhausted the local nesting population in the Cayman Islands and were sailing elsewhere to catch turtles. By 1900 it was believed that the Cayman Islands local reproductive population had become extinct, but current day monitoring programmes with the DoE have shown that there is a small glimmer of hope as the population numbers very VERY slowly start to recover – only time will tell!

It’s not just adults and juveniles that are taken for food: eggs are also taken as an aphrodisiac and  up to 20-30% of all nests in some parts of the world are completely poached. In some regions of Costa Rica where the famous arribadas of Olive Ridleys occur every year, ‘nesters’ dig up freshly lain eggs and sell them on the black market.

In the Cayman Islands, illegal take continues to be one of the most serious threats to our nesting population. Typically several turtles are taken each year. This represents a tremendous loss to the nesting population, which is still critically small.

Coastal development

As development on beaches continues to grow, light pollution and loss of habitat availability for nesting turtles is becoming more and more apparent. Light pollution from beachfront properties has detrimental effects on both the nesting females and the survival of their offspring. Females coming onto the shore to lay their eggs can be easily deterred from nesting or can become disorientated and can fall into swimming pools or become entangled in beach furniture or other obstacles. But the impact of lights on the hatchlings is even greater. Hatchlings will emerge from their nests at night, and are drawn toward the reflection of the stars and moon reflecting off the water’s surface which creates the lightest point in the natural environment. However with continued development hatchlings are being drawn away from the water toward the lights on properties at the back of the beach. A single light can cause hundreds of hatchlings to misorientate into roads and gardens leading to dehydration in the morning sun and increasing their chance of being killed by predators or vehicles.  

Climate change (CC)

CC has huge effects on many aspects of turtle ecology, from altering the sex of the hatchlings to potentially altering the distributions of adults and hatchlings. To recap last week’s blog: we learnt that the sex of the hatchlings is determined by the temperature of incubation in the middle third incubation period. An increase or decrease in the temperatures can lead to sex biased clutches, decreasing the chance of a female finding a mate as only females are being produced.  Additionally this increase in atmospheric and sea temperature can lead to an alteration in the world’s ocean currents. On the positive side, there is the potential for new foraging habitats and nesting areas to be created. However, ‘he who giveth can taketh away’, as current foraging and nesting sites can become destroyed through coastal flooding and intolerable temperatures for turtles. Therefore it is important that some nesting beaches be left undeveloped so that they can naturally migrate inland as the sea level rises.

Predation

At all stages of the marine turtle life cycle predation remains a constant threat. Feral animals (such as cats, dogs and pigs) can smell out a developing nest, while crabs, birds, sharks and other large predatory fish eat the hatchlings as they make their way down the beach and out to sea. As juveniles and adults their main predators are sharks and humans. If large numbers of nests are destroyed, there is no recruitment to the population and the population is diminished.

So just be thankful you are not a marine turtle! Here are but a few things that we can do to mitigate the impacts we have on marine turtles.

1.      If you are snorkelling or diving and you see fishing line or litter, remove it from the reef. Make sure that you cut the line so as not to damage any coral or sponges that might be entangled in the line.

2. If you witness anyone taking or molesting turtles in the Cayman Islands please call the Department of Environment Chief Conservation Officer at 916-4271 or 911. If you are reading this from elsewhere then please call your local authorities.

3.   Use turtle friendly lighting (TFL) on beach front properties. Not only will this positively impact  turtle populations but also your wallet! In places such as Florida, where it is the law for all beachfront properties to have TFL, they can have up to a 70% reduction in electricity bills. Interested? Then keep an eye out for the next blog or for more information visit our website: www.doe.ky

4. Remove beach furniture at night to prevent females from being discouraged from nesting and to prevent entrapment.

These are only a few things that you can do. Next time we will go into more detail about what you can do to your property to make sure you help protect these magnificent creatures!

Until the next time!

Luc J