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Sea Turtles Display Elegant Design Solutions; They’re Also Really Cute

Photo: Baby green sea turtle, by Tyler Karaszewski, via Flickr (cropped).

No doubt about it, from a scientific perspective, baby sea turtles emerging from their beach nests and crawling to the water on tiny flippers are extremely cute. Apart from their being adorable, what many may not realize is that their motion on the sand is also amazingly efficient. So much so that engineers are trying to imitate it to put to use in robots that need to traverse loose material.

Writing for Phys.Org, Daniel Goldman, a biomimetics engineer at the Georgia Institute of Technology, marvels:

The best robots people design and build can’t out-compete a hatchling sea turtle whose life consists of swimming all the time and using these appendages on land only for half an hour, running from the nest.” [Emphasis added.]

In a video from Georgia Tech Research Horizons, Goldman explains how flexibility of the turtle’s wrist is the key to its effective locomotion that can propel it down the beach at several body lengths per second over soft sand. The only other time the appendages are used for walking on land is years later, when the females crawl onshore to lay their eggs. For males, though, this once-in-a-lifetime sprint across the beach depends on well-designed legs that also work perfectly as swim fins for the rest of their lives at sea.

Here’s more on the turtle theme.

Glow-in-the-Dark Turtle

Night divers in the Solomon Islands were surprised to see a sea turtle glowing in the dark. They were filming a NOVA special, “Creatures of Light,” when a hawksbill sea turtle hovered like a bright red and green spaceship under their blue searchlights (the video below is via National Geographic). The beautiful stripes and patterns on its shell took on a new light as the turtle stayed with the divers for about five minutes.

This is the first observation of a glowing reptile. The glow is a phenomenon called biofluorescence: the ability to absorb light energy and re-radiate it (unlike bioluminescence, which emits chemical light). Biofluorescence has been known in fish, jellyfish, corals, and sharks. The divers and scientists are not sure how the turtle got this ability, or what function it plays in their ecology, but they were very excited to see this spectacular trait in a critically endangered species. Live Science tells more about the rare encounter.

Leg Warmers

Do sea turtles get cold feet? No, Science explains, because they are designed with large arteries and veins bundled within their leg muscles in a special way.

Despite having a low metabolic rate, leatherbacks — the sole living species of turtle in a once larger group — have a core body temperature that ranges between 25°C to 27°C (about 77°F to 81°F). Muscles must stay warm to remain efficient, but that’s a challenge for these beasts because they often swim in near-freezing waters, either in cold regions of the world or deep below the sun-warmed surface….

Besides the layers of insulating fat, which scientists knew about already, the team noted the unusual pattern of major blood vessels within the turtles’ leg muscles. The blood vessels are arranged such that veins carrying blood back to the body’s core give up heat generated within the ever-active muscles to the blood coming from the heart in arteries, the researchers report online today in Biology Letters.

This elegant solution not only keeps the muscles warm where the energy is needed. It also helps females not to overheat when performing the strenuous task of hauling their heavy bodies up the beach and digging nests. Consider, too, that the arrangement has to grow through several orders of magnitude from hatchling to adult and remain effective at all scales. The heat-transfer mechanism reminds me of the counter-current heat exchanger in the male testes of the humpback whale.

Turtle Diapers

What do sea turtles eat? To find out, researchers at the University of Queensland needed to collect fecal samples from loggerhead sea turtles. Finding a way to do that without hurting or bothering the animals was a challenge, but they finally came up with a flexible swimsuit design that fits over the turtle’s tail. The giant diaper worked perfectly, providing information that will help conservation efforts. 

Environmental Sex

Research from Florida Atlantic University highlights the little-known fact that sea turtles have no X or Y sex chromosomes. Instead, the sex of an individual is determined by the environment during incubation: “Warmer conditions produce females and cooler conditions produce males.” Under normal conditions, this arrangement has apparently worked out well. Understanding the turtle’s facts of life will be important, though, for predicting their response to changing climate. The article helps you appreciate what that adult turtle went through to reach breeding age:

Loggerhead turtles are already fighting an uphill battle since roughly one in 2,500 to 7,000 sea turtles make it to adulthood. The typical loggerhead produces about 105 eggs per nesting season and would have to nest for more than 10 nesting seasons over the span of 20 to 30 years just to replace herself and possibly one mate. And, if enough males aren’t produced because of climate changes, then this will result in a dire problem for this species.

Plastic Peril

Some humans are not helping the adults who make it past all those hurdles. The University of Exeter describes the problem of plastic pollution in the oceans. Beach litter — cups, straws, and bags — don’t just stay on the beach. They often drift far out to sea where turtles, fish, and marine mammals sometimes ingest them: “When turtles ingest plastic, they can suffer intestinal blockage that can result in malnutrition which can in turn lead to poor health, reduced growth rates, lower reproductive output, and even death.” 

Captain Dave Anderson, who appears in the Illustra Media documentary Living Waters, is a leading activist to rescue animals entangled in fishing nets and plastic. Whales, he points out, have been known to ingest deflated mylar balloons because from below they are mistaken for jellyfish, part of their normal diet. He is currently working on a low-cost tracking beacon that observers can attach to entrapped animals so that rescuers can locate them with the tools to cut off the nets.

We all have a responsibility to preserve a safe habitat for critically endangered animals like sea turtles. A few minutes of watching this viral video that shows rescuers trying to remove a plastic straw from a sea turtle’s nostril should cure most sensitive people of littering:

Success Stories

All is not bad news on the conservation front. PhysOrg says that endangered green sea turtles are nesting in record numbers in Florida, thanks to conservation efforts. The number of nests counted in state beaches rose in four years from 10,700 to 28,000. That represents a huge rebound from the low of 464 nests some three decades before. Green sea turtles nest on beaches in 140 countries. They are threatened by habitat loss and fishing nets, but “Measures in place to protect these habitats and the use of turtle-friendly fishing gear has helped numbers increase.”

Dr. Stephen Dunbar, who also appears in the Illustra film, is president of ProTECTOR, a conservation effort in Honduras that conducts research and also helps educate local fishermen and government officials about the value of sea turtles to the ecology. The acronym stands for “Protective Turtle Ecology Center for Training, Outreach and Research.” One of their innovative techniques is the “bottles to buildings” program, where citizens learn how to put trash to constructive use instead of throwing it in the ocean.

The Turtle Explosion

One more sea turtle story reports: “World’s Oldest Sea Turtle Fossil Discovered.” Live Science says that a fossil sea turtle 120 million years old — 25 million years older than the previous record — was uncovered in Colombia. There are two problems here for the Darwinian evolutionist. First, this turtle is not primitive, but already highly specialized, as if it just exploded onto the scene. The second is that it might not be related to living sea turtles, leading the discoverer to speculate that “other turtles later evolved in the same way from a separate ancestor.”

To make matters worse, the discoverer responded to resistance to his speculation by piling on more: “It shouldn’t be an altogether surprising theory, he added, because mammals, reptiles and other animals evolved separately several times to produce a variety of sea-dwelling animals.” There are strong reasons, though, to reject “convergent evolution” in favor of intelligent design.

This article was originally published in 2015.