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New Insights into Green Turtle Hatchling Behavior Unveiled

Recent studies indicate that green turtle hatchlings may ‘swim’ towards the surface of the sand instead of ‘digging’ their way out after hatching. This groundbreaking information holds significant potential for improving conservation efforts aimed at protecting declining turtle populations worldwide.

The findings, published in Proceedings B, were the result of research conducted by scientists at UNSW’s School of Biological, Earth and Environmental Sciences. They utilized a small device called an accelerometer to gain fresh insights into the behavior of hatchlings during their emergence from nests.

Green turtle eggs are typically laid in nests buried 30 to 80 centimeters deep. After hatching, the tiny turtles navigate their way to the surface over a span of three to seven days. However, because this critical phase occurs underground, researchers have had limited understanding of the early life events of these hatchlings.

Using this innovative method, the research team discovered that the hatchlings maintain a head-up position while moving vertically through the sand. Contrary to previous assumptions that they would dig by tilting sideways, the hatchlings instead rock back and forth.

“Imagining a hatchling emerging from its egg, completely obscured in darkness with no visible indicators of which way is up, it’s remarkable that they can still orient themselves and ascend,” explained Mr. Davey Dor, the lead researcher and a PhD candidate. “Our preliminary findings and the validation of this methodology pave the way for numerous new inquiries into sea turtle ecology.”

Challenges of Studying Underground Behavior

The iconic image of baby turtles scuttling excitedly across the sand towards the ocean is well-known, but the journey they take prior to this moment remains largely unobserved.

“It was around 64 years ago that the hatching process and emergence of sea turtles was first documented,” remarked Mr. Dor. “Since then, researchers have employed various techniques, such as installing glass viewing panels and using microphones, to monitor this elusive phase.”

Despite advancements, these methods have inherent limitations, hindering comprehensive studies on hatchlings’ initial days. “It’s easy to overlook how much energy these tiny creatures expend swimming through sand in complete darkness and with minimal oxygen,” highlighted Associate Professor Lisa Schwanz. “This vital phase occurs right beneath our feet, yet we lacked the necessary technology to truly grasp what transpires.”

To better investigate this obscure developmental stage, Mr. Dor collaborated with A/Prof. Schwanz and Dr. David Booth from the University of Queensland.

Miniature Accelerometer Backpacks

The accelerometers utilized in this study are instruments that detect changes in movement, speed, and direction, and have been previously applied in various animal studies.

“The accelerometer used in our research works by measuring acceleration across three different axes,” explained Mr. Dor. “It can track forward-backward, up-down, and side-to-side motions.”

This study marks the first time such an accelerometer has been used in observing hatchling behavior in a subterranean context.

The research took place at Heron Island, a designated green turtle nesting site within the southern Great Barrier Reef. The nesting season typically spans from December to March.

“After locating the nests, we patiently waited around 60 days for the eggs to mature,” stated Mr. Dor. “Three days prior to anticipated hatching, we positioned a device known as a hatch detector next to ten nests, which alerts us when the hatchlings break free from their eggs.”

Upon confirming that the eggs had hatched, the team carefully excavated the nests, selecting the hatchling closest to the surface for attaching a lightweight accelerometer before gently replacing the sand. “It was then a matter of waiting for emergence,” noted Mr. Dor.

Every three hours, the team checked the nest sites until they were able to collect data from the hatchlings as they emerged. “Our analysis revealed consistent head-up positioning among the hatchlings despite the total darkness, and that their movements resemble swimming rather than digging,” Mr. Dor added. Furthermore, it was observed that movements are short and tend to peak during nighttime.

Implications for Conservation and Nest Management

Global sea turtle populations are facing significant decline, with several species classified as endangered. The nesting phase presents particular vulnerability, compelling conservation initiatives to focus on nest interventions like relocation and shading.

While nest relocation has been widely practiced for years—especially as climate change and rising sea levels threaten nesting habitats—the implications of changing nest conditions are not fully understood. “Modifying nest characteristics, such as moisture levels and substrate depth, could adversely affect hatchling capabilities,” cautioned Mr. Dor.

Understanding hatchling behavior in their sandy environment is crucial for informing future conservation strategies. As emphasized by A/Prof. Schwanz, “While many hatchlings face predation during their journey to the ocean, it’s important to recognize that a lack of knowledge exists regarding why some hatchlings succeed in emerging while others do not.”

Expanding Research Horizons

The findings from this research highlight the advantages of utilizing accelerometers for monitoring hatchling behavior, offering novel data on movement patterns during a phase that has historically been shrouded in mystery.

These insights not only challenge previous assumptions regarding early hatchling behavior but also underscore the need for further research. “Many factors related to this life stage remain unexplored, and we hope this new methodology will enhance our understanding, particularly regarding optimal conservation practices,” said Mr. Dor.

In the following summer, Mr. Dor plans to return to Heron Island to utilize accelerometers on multiple hatchlings from a singular nest, aiming to explore theories about potential coordinated movements among hatchlings. “This could provide further clarity on whether turtles coordinate their actions or engage in a division of labor during their ascent,” concluded A/Prof. Schwanz.

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