In search of a Leviathan

[Rainbirder]

Back in mid November 2001 I received a rather bizarre phone call from a friend who told me that a marine turtle had turned up only 5 miles from my home in the upper Firth of Forth (an estuary) on the east coast of Central Scotland. A turtle in eastern Scottish waters at the onset of winter was surely doomed & so a small 'rescue party' of divers & marine biologists was put together in an attempt to save the animal. Strangely what they found was a huge, fit & healthy Leatherback turtle that had no wish to be rescued and so the animal was left to its own devices, shortly following which (and before I got a chance to see it!) it left the Forth under its own steam. The whole incident was both fascinating and intriguing but made the disappointment in not seeing the animal all the more poignant! A turtle that could survive in Scottish waters had to be something special and so began a strong desire to see one of these amazing beasts for myself.

 

(A poor quality scanned image from a newspaper clip of the River Forth Leatherback.

The initial photograph was taken by Dr Kevin Robinson of the Cetacean Research and Rescue Unit.)

 

 

Three years later in October 2004 I was on a family holiday in the Seville area of Spain. We took a trip into Coto Doñana National Park on one of the large green 'dune-buses' which, following a circuit of the southern part of the reserve returned to the El Acebuche visitors centre along the beach east of the resort of Matalascanas. En-route the bus stopped briefly to show us the carcase of a turtle which had been washed up onto the beach. The body was decomposing but was quite clearly that of a Leatherback Turtle. The trip guide explained that with a diet mainly consisting of jellyfish Leatherbacks are prone to the accidental ingestion of plastic bags (a floating plastic bag can look very much like a jellyfish) which they are unable to regurgitate and which causes a painful death through intestinal obstruction. Apparently the carcase of the Doñana turtle had been examined in-situ and this had been deemed the cause of its death. Upon returning home I felt compelled to obtain further information on Leatherbacks, there were some details available on the web however it was apparent that a lot remained unknown about the biology of these huge reptiles and the scant information available was dominated by some very pessimistic population reports! Essentially there has been a catastrophic decline in Leatherback numbers with the worldwide population having fallen to only 20-30,000 adult females by 1996 from a population of around 115,000 in 1982 (i.e. a massive decline of 78% in only 14 years). Given this dramatic decline coupled with a huge natural range it was obvious that I would never be likely to see a living Leatherback in the flesh!

(Dead Leatherback -killed by intestinal obstruction after accidental ingestion of a plastic bag. Matalascanas, Donana, Spain.)

 

 

 

 

In May of 2006 my wife Marian and I hastily organised a last minute one week Spring break away from the pressures of work & family. We decided upon the Caribbean but wanted something other than sun and sand so ended up on a plane bound for the twin island nation of Trinidad and Tobago. It was perhaps too far for a one week holiday and in effect we only really had 6 full days but we were able, at short notice to book accommodation at the Asa Wright Centre in the northern hills of Trinidad. We were very fortunate as the AWC had surprisingly few other guests giving us freedom to explore the numerous trails without noisy disturbance.

 

(View from the Asa Wright Centre Verandah looking down the Arima Valley)

 

 

The stay at Asa Wright was simply a mind-blowing experience which was complimented by a range of full day & half-day excursions to various sites of interest. We booked 2 full day & 2 half-day trips with one of the trips on offer being a night-time excursion to a turtle nesting beach. We were told that views of turtles couldn't be guaranteed but we thought that the chance of watching a Green Turtle or perhaps a Hawksbill hauling-up to nest was too good to miss so we decided to book the trip. Excursions to see nesting turtles are tightly controlled as each visitor requires a permit & has to be accompanied by a local warden whilst on the nesting beach. The AWC staff can organise all of this and in addition supply transport with a knowledgeable guide whilst also supplying a hot picnic meal. Our guide for the trip was to be Dave Ramlal & we were surprised to find that we were the only couple booked up for this trip. Dave proved to be very knowledgeable, great company & a truly top-class birder. To our delight he explained that yes Green or Hawksbill turtles were an outside possibility but that really the beach we were planning to visit was a Leatherback nesting beach!

 

Our trip began at 4:00pm when we left the Asa Wright Centre driving down the Arima valley before heading east to the atlantic coast. We were told the trip would take 70-90 minutes depending on traffic & unscheduled birding stops. Our first stop was at Verdant Vale (Temple Village) in the lower Arima valley where a Short-tailed Hawk was seen hunting over adjacent forest followed by a White Hawk hunting over a hillside by the road. On stopping Dave heard a calling Striped Cuckoo which he quickly found for us followed by a Trinidad Euphonia (sadly I left my long lens at Asa Wright -not thinking I would need it ). We continued on heading east towards Valencia. Further stops provided Savannah Hawk & a number of Plumbeous Kites before we eventually headed towards the Toco region & Matura. On arriving at Matura Dave stopped to organise our warden/guide with a group of local volunteers collectively called Natureseekers -of which he was also a member. We then drove down along a rough forest track to Matura beach.

(Corbeau through a heat-haze -American Black Vultures)

 

(Black Vultures in their roosting tree)

 

As the sun was setting we parked up by a large open-sided shelter & ate our evening meal -a delicious mixture of vegetable & chicken curries with roti -and all washed down with Asa Wright's famous rum punch. Nearby a large dead tree was holding increasing numbers of roosting Black Vultures as darkness quickly fell. Whilst we were finishing our meal it began to rain - a brisk heavy short-lived tropical downpour of warm rain which proved quite refreshing after the soporific effects of the rum punch! Within about 20 minutes the rain stopped & the dark skies quickly gave way to a rich display of stars. Dave pointed out the Southern Cross in the sky whilst suddenly all around us there seemed to be an eruption of small stars twinkling as fireflies lit up the night. Neither of us had ever seen a display of fireflies like this -it appeared surreally magical & has burned a lasting impression in our memory! The remnant of our picnic was quickly cleared away and we followed Dave down to the shoreline where we met a couple of the local guys from Natureseekers. Whilst one of them went off with Dave to start patrolling the beach we were left in the company of Dexter -whose thick Trinidadian accent we initially found difficult to follow. As we became attuned to Dexter's Trini-talk it was apparent that he was a man with a considerable knowledge of the biology and behaviour of Leatherback Turtles. It was also clear that he and his colleagues (all local people) shared a great passion and caring for their turtles taking turns to patrol the nesting beaches overnight throughout the nesting season. As a Brit I have been rather guilty of holding an unspoken chauvinistic belief that nobody cares about wildlife as passionately as us; well how arrogant, naive and wrong is that? The guys from Natureseekers are unsung heroes devoting considerable time and effort whilst enduring considerable personal discomfort in their endeavours to protect the Leatherbacks; I was truly amazed and humbled by their energy, devotion and passion.

 

Dexter described the very instinctive and stereotyped behaviour of nesting Leatherbacks. He advised us that 'incoming' females are easily spooked and will abandon partially dug nests if there is any hint of disturbance. However once the nest is fully excavated and laying has began the turtles enter a bizarre hypnotic state during which time they can be touched, measured, tagged and even flash-photographed. Once egg-laying is complete the turtles adopt their previous wary state and disturbance has again to be minimized. Dexter went on to explain the threats and dangers to nesting Leatherbacks and their offspring which on Trinidad includes not only human disturbance but also threats from feral dogs, Crab-eating Racoons and Corbeau (the Trini name for Black Vultures) whose high numbers in the Matura area are in large part due to the presence of turtle-nesting beaches. Occasionally hatchlings will appear on the beach in daylight -these youngsters are collected and held over for release the following night. The hatchlings have a strong attraction to light -an adaption which would normally draw them down to the water's edge when hatching under the cover of darkness, however lighting from coastal villages, vehicles or flashlights can easily disorientate them leading to youngsters wandering off in the opposite direction to the sea with sad and predictable results. We watched as hatchlings were released into the surf and were given the opportunity of holding a few before releasing them into the moonlit waters -we were amazed by how powerful and effective their wing-like front flippers were and how quickly the hatchlings disappeared into the darkness beyond the Atlantic swell.

 

(Marian holding two Leatherback hatchlings just prior to release)

 

 

Whilst releasing hatchlings Dexter's walkie-talkie radio crackled into life and we were summoned to attend a nesting female Leatherback about 700metres further along the beach. This female had been observed from a distance as she lumbered up the beach. We were invited to attend when she had almost completed digging her nesting hole. We walked along the surf till we came upon the female's tracks leading from the sea up the beach. The tracks were bizarre in their pattern with a surreal span almost suggesting the caterpillar tracks of a JCB rather than a turtle; nevertheless the large tracks failed to prepare us for the shock of finally seeing this huge reptile in the flesh. This particular female seemed massive in both length and flipper span even though her full bulk was hidden by her partial submergence in the nest cavity. Later when we watched her return to the sea her immense bulk looming in the darkness looked more like a family saloon car than a turtle (ok, a wee bit of hyperbole here!). As the female completed the final stages of her excavations we were treated to a close-up view of the process. The turtle creates a large shallow depression with her front flippers before moving forward into this allowing her to use her hind flippers to dig the nest hole itself. The hind flippers are massive exceedingly flexible spade-like 'hands'; the right hind flipper was rolled around into a cylindrical funnel which was inserted deep into the sand before the end was flexed back forming a scoop -the whole flipper then being raised up & rotated to the right before the sand was deftly flipped well away from the hole. All of these flipper movements seemed to occur as a series of staccato uni-directional 'pre-programmed' mechanical movements more like a machine than an animal. When the right flipper had completed a single 'scooping' cycle the massive reptile's body heaved violently to the right so that the left hind flipper could complete a digging cycle before the carapace shifted back to the left for the right flipper to take over. By this series of alternating stereotyped actions a deep nesting hole was dug prior to laying.

 

(A massive female Leatherback)

 

Up to this stage the only lighting had been a single dim red-filtered light but at the appearance of the first egg flashlights were switched on and we were invited to approach closely and gently explore the animal. Leatherbacks are called leatherbacks because they have a leathery almost fleshy carapace as opposed to the thick armour-plated bony scutes of more typical sea turtles. The front flippers are massive powerful wing-like structures which effectively row these large creatures across oceans and pull their massive bulks up the nesting beaches. Our huge female had jelly-like material streaming from both eyes giving her an appearance of extreme discomfort -like a bad hay-fever sufferer. This thick 'eye' mucous is in fact very concentrated brine -produced by salt glands adjacent to the eyes; Leatherbacks swallow a lot of seawater whilst feeding and thus need a mechanism to excrete this excess salt. Normally in water the mucous washes quickly away and there is no build-up however nesting females develop a significant amount of this mucous around the eyes which offers useful protection to the eyes from mechanical abrasion by sand grains.

 

(A female Leatherback in a trance-like state whilst laying)

 

(During egg-laying the females are almost totally unresponsive)

 

(It's hard to get an idea of scale from these images but the eggs are about the size of a hen's egg but are round and shell-less. The hind flipper is massive. This female has probably laid about 3-4 times already this season. After laying she returns to sea & mates again (males station themselves offshore of the nesting beaches), possibly also feeding again if given a chance. A large female can complete 5 or 6 of such laying cycles in a season but this clearly exhausts her fat reserves & puts her under great strain. It is thought that breeding females probably don't nest every year.)

 

(Towards the end of her egg-laying this female produced a number of small infertile eggs. Studies done on 'managed nests' where the small non-viable eggs are removed reveal that these small eggs fulfill a useful function as they pop under pressure preventing excessive compaction of the nest.)

 

Eventually our female completed her egg-laying so we retired to a safe distance to allow her to infill the nest; following which she dug a number of adjacent shallow pits -it was explained to us that these were 'decoy' nests which were meant to draw attention away from the main nesting chamber. Finally our female, satisfied with her nest-camouflage hauled herself down the beach and into the surf leaving us with the abiding memory of her massive body melting into the dark ocean swell. We barely had time to catch a breath following this amazing experience before we were directed to a smaller female who had not been previously tagged. We watched whilst she began to lay and whilst in a torpid egg-laying trance tags were applied to one of her hind flippers and her biometrics were recorded.

 

(The team prepare a hind flipper for tagging whilst the female is in her egg-laying "trance")

 

(A tag is applied. Note the briny mucous around the eyes.)

 

 

We were invited to touch this female (she felt strangely warm to the touch), assist in recording her measurements and I was also permitted to take a few flash photographs. Whilst many of the females have had simple tags applied a few have had radio-telemetry devices fitted to trace their movements –the results have been astounding (see below)!

 

(The flippers are massive and they feel warm to the touch)

 

(We were told that this female Leatherback was of modest-size but clearly these are big beasts!)

 

 

 

Thoroughly satisfied with our trip it was time to head off back to Asa Wright. The first part of the journey involved negotiating the pothole-ridden forest track back to the main road -a bit of a white-knuckle ride in the dark but well-compensated by the numerous Parauque (a neo-tropical Nightjar) present. We arrived back in our cabin at Asa Wright well after midnight tired but supremely happy and with a five year quest fulfilled!

 

 

 

Some facts about Leatherback Turtles:

 

Leatherbacks are the largest species of turtle with mature females being huge and adult males being even larger! The largest ever found was a little over three meters from head to tail and weighed over 900 kilograms (almost a ton!). That particular specimen was found on a Welsh beach in the UK!

Leatherbacks are the World's fourth largest reptile (only Saltwater Crocs, Nile Crocs and Gharial being larger).

 

Atlantic Leatherbacks breed mainly on a few scattered isolated beaches in the Caribbean, Central/South America and equatorial West Africa. After breeding they disperse widely with young animals remaining in offshore tropical waters. However, radio-telemetry has revealed that large mature Leatherback turtles cover massive distances on trans-Atlantic trips which carry them up into the North Atlantic off the east coast of Canada and across into the Celtic sea and the coastal waters of Scotland, Ireland and Wales. The waters to the west of the British Isles experience a massive seasonal bloom of plankton growth from May into August which encourages huge populations of jellyfish which the large Leatherbacks seek out to feed on. Adult Leatherbacks feed almost entirely on jellyfish, tunicates and small cephalopods. They have backward pointing spikes in their pharynx/upper oesophagus which aids in the capture and swallowing of slippery prey such as jellyfish. As a jellyfish is caught and swallowed a large amount of seawater is also ingested. After swallowing a jellyfish they regurgitate it against the pharyngeal spines which strains out the water and leaves behind the edible material which is swallowed and digested. Unfortunately this also prevents Leatherbacks from regurgitating & spitting out swallowed plastic bags which they mistake for Jellyfish!

Autopsies of dead leatherbacks have revealed that they have huge stomachs, often filled with masses of relatively low-calorie jellyfish, stingers and all! The gelatinous body of a jellyfish is effectively comprised of about 98% seawater and so Leatherbacks have massive salt glands near the eyes which collect excess salt from their systems and excrete it as viscous brine tears. Jellyfish offer little nutrition and sustenance. Like pandas eating bamboo, Leatherbacks have to eat a lot of jellyfish and spend a lot of time eating just to get enough calories to power their large bodies. By some estimates leatherbacks need to eat their weight in jellyfish every day to get the nutrition they need. One turtle was filmed devouring 60 lion’s mane jellyfish in three hours (these large northern coldwater jellyfish can have “bells” over 50cm in diameter).

The Leatherback turtle has been described as being one of the finest hydrodynamically designed animals on the planet. Whilst very awkward on land it moves with amazing grace and ease in the water. Normally Leatherbacks travel at a sedate pace of 1.5-2 mph but they have been clocked swimming at the incredible speed of 21.92 mph (as fast as a sprinting man!). Such speeds are achieved as a consequence of the large powerful front flippers which are powered by special temperature-independent muscles. Other physiological adaptations include specialised blood which contains more red blood cells (with more haemoglobin per blood cell) than any other reptile, large reservoirs of myoglobin in the muscles and a massive powerful heart which with an unusual shunting arrangement can allow partially oxygenated blood to bypass the lungs, which become almost completely collapsed during deep dives. Effectively all of these adaptations are designed to ensure the maximum delivery of oxygen to the muscles even when the animal is unable to take a breath!

Leatherbacks have a number of unique physiological adaptations for life in colder waters. They lack a bony shell but under their leathery skin is extensive oily brown adipose tissue which has insulating qualities and may help generate metabolic heat (a feature more typical of an endothermic mammal than a “cold-blooded” reptile). They also have temperature-independent swimming muscles which remain active even in the cold and generate heat from this sustained activity. Finally they have counter-current heat exchangers between the large front flippers and the core body, as well as an extensive network of counter-current heat exchangers surrounding the trachea (wind-pipe). However, rather than depending upon a high resting metabolism, leatherbacks appear to generate body heat as a consequence of a high physical activity rate. Studies on wild Leatherbacks revealed that individuals may spend as little as 0.1% of the day resting. This constant swimming creates muscle-derived heat which coupled with their counter-current heat exchangers, insulating fat and large size, allow leatherbacks to maintain high temperature differentials compared to the surrounding water. Indeed adult Leatherbacks have been found with core body temperatures that were 18 °C (32.4 °F) above the water they were swimming in and have been found actively hunting in waters as cold as 0.4°C.

 

Tagging and telemetry studies undertaken in the Irish Sea have revealed that Leatherbacks will occasionally make very deep dives –to depths thought to have been well beyond the limit achievable. A Leatherback radio-tagged off the coast of County Kerry in Ireland in June 2006 was subsequently recorded making a dive of 1.25 kilometres (1250m!) –a feat previously thought impossible for such an animal. At these great depths the water column temperature is not much above 4°C and the water pressure is a massive and bone-crushing 1,472 pounds per square inch (101 bar)! It is thought that wandering adult Leatherbacks make these occasional deep dives during the day to check for the presence of deepwater jellyfish which spend daylight hours in deep water but rise up the water column at night to feed on plankton.

 

The facultative endothermy of Leatherback turtles together with other adaptations in their anatomy and physiology mean that in many respects these wonderful creatures are more like marine mammals than like other turtles.

Sadly as the World's Oceans become increasingly polluted with plastic detritus more & more adult Leatherbacks are killed. Time is running out for this charismatic reptile with populations in the Atlantic, Pacific and Indian Oceans in free-fall. As an example the beach of Rantua Abang in Terengganu, Malaysia once had the largest nesting population of Leatherbacks in the world, hosting 10,000 nests per year but by 2008 only two nests were found there and unfortunately the eggs were infertile! The IUCN have now listed the Leatherback Turtle as critically endangered (the last category before extinction)!

I was amazed when I first discovered that these astounding reptiles are actually part of Scotland’s natural heritage but unfortunately it now looks like these leviathans are headed for extinction. So if you ever get the chance to see a Leatherback turtle seize the opportunity! And don’t forget to use alternatives to the plastic bag when you next go supermarket shopping as these are the very bags which end up in our oceans!

 

Some links:

http://www.nesbiodiversity.org.uk/pdf-files/Roadshow%20leaflet.pdf

 

http://www.swan.ac.uk/bs/turtle/reprints/INTERREG%20IIIA%20Irish%20Sea%20Leatherback%20Turtle%20Project%20-%20Final%20Report.pdf

 

http://jeb.biologists.org/content/211/16/2566.full.pdf

Edited April 22, 2012 by Rainbirder

[egilio]

A very thorough story! I personally witnessed leatherbacks in St. Lucia back in 2006 while volunteering there for Durell Wildlife. Sadly I also found about 25 poached leatherback turtles.

Contrary to the main believe leatherbacks don't necessarily return to the beach where they were born to lay eggs. They return to the same region, and can lay up to 9(!) nests in a year they breed (females don't breed every year) and nests can be made at several different beaches from several different islands in the same year.

The atlantic population is doing far better than the population in the pacific which seems to be down to less than 5,000 animals. The invention and large scale use of degradable platics could have a big positive effect on the survival of this species.

[PCNW]

Interesting, thank you. Patsy

[Game Warden]

Is anyone having a problem with the images not displaying properly?

[Rainbirder]

Is anyone having a problem with the images not displaying properly?

 

Yes, I am.

Only about half of the images I have posted are being displayed.

They were all displayed last night when I first posted the thread.

I've had a few problems like this before when direct-linking to images on Pbase.

 

Matt are you able to allow me to re-edit this thread so that I can link the same images from a different source (Flickr)?

[Game Warden]

Ok have a go now. Matt

[Rainbirder]

Ok have a go now. Matt

Cheers!!!

[Rainbirder]

Seems to be working now.

[kittykat23uk]

Great report! We had a leatherback turtle surface right next to our boat while diving off the coast of Tofo Mozambique last year. Sadly I didn't get a photograph, but it was an amazing sighting.

[Atravelynn]

Images work fine for me. Great report. I'm glad you encountered people intent on maintaining an environment for the turtles to continue to lay their eggs. They need advocates. Your 10,000 nests to 2 is startling.

 

I've seen only one leatherback lay eggs on the beach at night then drag herself back to the ocean. One of the most moving wildlife encounters I've ever witnessed.

 

Thanks for wonderful account. You had perfect timing for the turtles.