Sea turtle nest relocation Relocation is a key on-site measure to save eggs—which would otherwise be lost to waves, erosion, or tourists—by moving them to a shaded, safe zone. However, does simply moving eggs to a cooler, shaded area yield the same results as the original nest? A study comparing 48 green sea turtle nests on Heron Island, Australia, over two nesting seasons suggests that this may not be the case.
Although nests moved to the shade had average temperatures similar to those in their original locations, outcomes regarding hatching success, hatchling size, and righting performance differed. In other words, a nest is not merely a thermometer buried in the sand; it is a miniature ecosystem where moisture, airflow, sand structure, and the microbial environment interact.
30-Second Summary
- Researchers categorized 48 green sea turtle nests on Heron Island during the 2022–23 and 2023–24 seasons into three groups: in-situ (left in place), relocated to shade, and relocated to sun exposure.
- The overall average temperatures were 29.1°C for in-situ nests, 28.8°C for those relocated to shade, and 30.9°C for those relocated to sun exposure.
- Despite having temperatures similar to in-situ nests, those relocated to shade showed lower hatching success and poorer indicators of hatchling quality.
- The study does not conclude that nest relocation should be stopped; rather, it suggests that when relocation is unavoidable, factors beyond just temperature must also be managed.
What happened?
Published in *Marine Biology*, this study conducted a field experiment on Heron Island, at the southern end of the Great Barrier Reef, comparing natural nests with two types of relocated nests. Researchers assigned treatments—leaving eggs in the original location, moving them to a shaded hatchery, or moving them to a sun-exposed hatchery—and recorded temperature, incubation duration, hatching and emergence success, and hatchling morphology and locomotor performance.
| Category | Details |
|---|---|
| Common Name | Green sea turtle |
| English name | Green turtle |
| Scientific name | Chelonia mydas |
| Classification | Order Testudines, Family Cheloniidae |
| Distribution | Tropical and subtropical oceans and nesting beaches worldwide |
| Conservation Status | IUCN Global Status: LC (Least Concern, 2025); some regional populations have separate risk classifications |
“Temperatures and results observed in 48 nests
The average temperatures over the entire incubation period were 29.1 ± 0.15°C for in situ nests, 28.8 ± 0.13°C for shaded translocated nests, and 30.9 ± 0.13°C for sun-exposed translocated nests. The difference between in situ and shaded nests was not statistically significant (P=0.26). However, the average temperatures during the final two weeks of incubation rose to 32.8°C, 33.2°C, and 35.1°C, respectively. Median incubation periods were 63 days for shaded nests, 60 days for in situ nests, and 54 days for sun-exposed nests, aligning with the temperature differences.
Outcomes could not be explained by temperature alone. Hatching success was higher for in situ nests than for shaded translocated nests (P=0.04) and sun-exposed translocated nests (P<0.001). In situ nests also showed higher emergence success compared to sun-exposed translocated nests (P=0.009). Notably, despite similar temperatures between shaded translocated nests and in situ nests, the shaded treatment resulted in smaller hatchlings and poorer self-righting performance. This discrepancy is the focus of the study.
Why did outcomes differ despite similar temperatures?
The relocation process can alter factors such as nest depth, sand particle size and compaction, moisture levels, gas exchange (oxygen and carbon dioxide), and the surrounding microbial conditions. While the study measured these variables, it did not pinpoint a single cause. Thus, the findings do not prove that shade is inherently harmful; rather, they indicate that adjusting the temperature via shading does not necessarily replicate the microenvironment of the original nest.
What do the sex ratio figures actually tell us?
An analysis of gonad tissue from hatchlings in 2023 revealed the following male ratios: 73±23% for on-site nests, 55±35% for shaded nests, and 8±7% for sun-exposed nests. For species like green sea turtles, where sex is determined by temperature, the link between high temperatures and a female-biased sex ratio is significant. However, these figures are based on samples from specific nests over a single season and carry large margins of error; they should not be extrapolated to represent the sex ratio of the entire Heron Island population or the species as a whole. Research on temperature-dependent sex determination at the cellular level Research on primary cilia determining turtle sex can also be found elsewhere.
Implications and limitations for conservation
Relocation remains a life-saving option for nests at imminent risk of loss due to sea-level rise or erosion. The researchers’ message is that nests should be left in place whenever possible; if relocation is unavoidable, factors such as sand type, depth, moisture levels, and gas exchange—not just temperature—should be standardized, and post-relocation outcomes monitored. Since the findings are based on 48 nests on a single island, further testing is needed to see if the same effects occur across different beaches, populations, and seasons.
The IUCN is planning a global for 2025 Although the green sea turtle is assessed as Least Concern (LC), the status of regional populations varies. An improvement in the global status classification should not be mistaken for safety across all nesting sites. The broader context of climate pressures is Climate change and reptiles, and how to interpret an animal’s condition through its behavior research on tortoise emotions leads into this.
Key takeaway
- The outcome of nest relocation is not determined by temperature alone.
- Relocated nests and in-situ nests yielded different results despite having similar average temperatures.
- The sex ratio figures represent a single season’s sample and do not constitute a conclusion for the species as a whole.
- Relocating risky nests may be necessary, but it requires more sophisticated microenvironment management.
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Original source, DOI, and references
- Original paper by Wood et al., Marine Biology — DOI 10.1007/s00227-026-04926-2
- UNSW research overview
- IUCN Marine Turtle Specialist Group assessment status
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