Cold-stunned turtles

Banana boxes? Check. Air support? Check. Volunteers? Check. After several years’ experience, conservation groups on Cape Cod know exactly what they need to rescue sea turtles that wash up on their shores every winter. But how do these turtles end up stranded in Massachusetts, USA, a place that seems so far from their usual tropical waters?

Sea turtles come and feed in Cape Cod bay during the warm summer months. Come the colder months, the turtles migrate back to warmer waters in the South. However, due to the geography of the Cape, some turtles cannot navigate their way out of the bay and get trapped. As the water cools these cold-blooded animals suffer from hypothermia, loose their ability to move, and wash up on the shores of the Cape.

Fortunately volunteers patrol the beaches to help the turtles. The cold-stunned turtles are taken to an animal care centre, such as the New England Aquarium, where they receive medical treatment. The turtles’ body temperatures are gradually raised every day and their progress is carefully monitored. Full recovery can take anywhere between a few days and several months, after which the turtles are placed in specially prepared banana boxes and are either flown or driven back South and released in warmer waters.

An improvised turtle centre. (photo courtesy of Liz Maloney)

The cold-stunned turtles are cared for at rescue centres
(photo courtesy of Liz Maloney)

This year, for the first time since the start of the rescue activities, volunteers are recovering turtles from the beach as late as January. This may be due to rising temperatures, which causes the turtles to migrate south later in the season. Already over 500 cold-stunned turtles were reported this season, amongst which are Kemp’s ridley, loggerhead, and green turtles. In 2014 a record of 1200 turtles were recovered from the beaches around the Cape. Thanks to the efforts of the volunteers and rescue centres, the majority of these turtles made it back home safely.

a turtle in a box (photo courtesy of Liz Maloney)

Getting ready for the trip home!
(photo courtesy of Liz Maloney)

The importance of rainfall

Sea turtles lay their eggs in underground nests on sandy beaches. The eggs are then left to incubate unattended and are subject to a suite of environmental conditions. The interplay of these environmental variables affects important factors such as the development rate and hatch success of the nest.

Since sea turtles exhibit temperature-dependent sex determination, the incubation temperature of the egg also determines the sex of the offspring. Warm incubation temperatures (typically above 29 °C) lead to a majority of females being born whereas cooler temperatures lead to males being born.

A new study published recently in Endangered Species Research shows the importance of rainfall throughout the incubation process. The researchers from Florida Atlantic University (USA) recorded rainfall and sand temperatures at a loggerhead turtle nesting beach in Florida. Ms Lolavar, the lead author of the study, tells me that the results of the study show that “heavy rainfall events can cool the sand and bring the incubation temperature of a nest in the male-producing range. However, if beach temperatures are too warm, which is often the case in Florida, most rainfall events don’t shift the nest temperature enough to produce males.”

This is not a phenomenon limited to Florida of course. A 2007 study of leatherbacks nesting in Grenada showed similar results. What sets the new research apart is that the Florida researchers also determined the sex of hatchling sea turtles laparoscopically. This enabled them to empirically show that during particularly rainy nesting seasons more male turtles hatched.

Ultimately, this study shows that understanding the effect of rainfall on incubation temperatures is key to anticipating the effects of the changing climate on sex ratios, and thus for the successful long-term conservation of sea turtles.

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Loggerhead hatchlings: are they female or male?

Titanium turtle

Every year boat strikes contribute to the anthropogenic mortality of several threatened marine species including sea turtles, manatees, dugongs, and whales. A boat strike will often result in severe injury and the animal’s death.

However, for the male loggerhead turtle “Akut-3” the story is different. The turtle, named after the Search & Rescue Association that found him, was taken to the DEKAMER Sea Turtle Research, Rescue and Rehabilitation Centre after he was found badly injured and floating off the shores of Turkey. Akut-3 had visibly had a close encounter with a boat propeller: he suffered from severe facial wounds and a fractured jaw. With over 60% of his jaw missing and unable to feed anymore, this turtle’s fate seemed sealed.

The only hope was total facial reconstruction. Working in collaboration with BTech Innovation A.Ş. the veterinary surgeons designed an implant for the turtle and had it 3D printed using medical-grade titanium. After a successful operation, Akup-3 is still recovering at the DEKAMER Centre.

This is the first time a sea turtle benefits from 3D printing technology. As of yet, the turtle does not show any signs of rejecting the implant but it will take time before it is confirmed that the operation was a complete success. Let’s hope that the turtle can be fully rehabilitated and released back into the wild!

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Photos courtesy of BTech Innovation A.Ş..

Geomagnetic navigation

Sea turtles carry out long-distance migrations between their feeding grounds and their breeding grounds. For example, some green sea turtles feeding off the coast of Brazil migrate over 2000 kilometers to Ascension Island in the middle of the Atlantic. But how do the turtles navigate the oceans? One hypothesis is that they use Earth’s magnetic field for navigation. This was once tested by attaching powerful static magnets to turtles and seeing if it would impede the turtles’ navigational skills. Results from such studies were the first field evidence for the involvement of geomagnetic cues in sea-turtle navigation.

In a new research published recently in the scientific journal Current Biology, researchers from the University of North Carolina were interested in knowing if marine turtles could imprint on the geomagnetic signature of their natal beach and use that information to return to it year after year. Their starting hypothesis was that if turtles imprint on their natal beach using a geomagnetic signature, the turtles would nest at slightly different locations year after year since Earth’s magnetic field shifts slightly over time. To test this they mapped out 19 years of loggerhead turtle nesting data along the Atlantic coast of Florida. They observed that nesting locations would vary from year to year with some beaches being more popular than others depending on the year. They then examined how Earth’s magnetic field changed at their study site over the same period of time and found that there was indeed a strong association between the spatial distribution of turtle nests and subtle changes in Earth’s magnetic field. So it would seem that turtles are able to imprint on their natal beach’s unique geomagnetic signature and use this information to return there to nest!

James Gould, a professor in Ecology and Evolutionary Biology at Princeton University, reports in Current Biology that this is an “extremely clever analysis” in which the authors of the study took “initially unpromising data” and looked at it in an “entirely new way.” But what is the reason for a turtle to return to the beach where she was born in order to nest? J. Roger Brothers, one of the authors of the paper, says: “The only way a female turtle can be sure that she is nesting in a place favourable for egg development is to nest on the same beach where she hatched. The logic of sea turtles seems to be that ‘If it worked for me, it should work for my offspring.'”