Coastal crabs are silent killers of baby turtles

A new study sheds light on the grim reality of newly hatched Loggerhead turtles along Australia’s west coast: a frenzy orchestrated by the golden ghost crab.

These rapid nocturnal predators proved to be a surprisingly deadly threat to endangered larvae, challenging the previous assumption of what and in which way these fragile creatures fell their prey. Researchers at Edith Cowan University (ECU) and Biodiversity, Conservation and Attractions (DBCA) used infrared photography to observe these attacks, revealing the details of predation previously hidden in dark and remote areas.

These findings, published in the journal Food Network, suggest that ghost crabs, while omnivorous animals are effective predators for turtle eggs and hatched predators, are fully understood than before. This new insight raises concerns about the long-term survival of the Loggerhead Turtle population, which have been classified as endangered.

Revealing Night Attacks

It is difficult to study how to prey on turtles’ hatcheries, especially at night and far away without disturbing natural behavior. To overcome this, the researchers used infrared photography along the Ningaloo coast of Bungelup Beach and Gnaraloo Bay. This allows them to observe the feeding habits of golden ghost crabs in natural habitats and in controlled aquarium environments in Minderoo Exmouth Research labs.

Previous studies often rely on indirect evidence, such as interference with turtle nests or expected number of eggs. “Previous research was limited to evidence of Loggerhead Turtle Nest perturbation and egg count. Although once the mechanism of hatch predation appears from the nest,” said Dr. Casper Avenant, an auxiliary lecturer at the ECU and lead researcher of the researchers.

Methodical and cruel

The hunting method of the golden ghost crab is systematic. When encountering a tortoise egg, the crab often creates unique gaps in the shell, consuming items through this opening. For hatcheries, the attack is more direct. Ghost crabs usually use large claws to tie baby turtles to their necks.

The smaller claws then start working, cutting the soft skin around the neck, partially or completely cutting the head. The crab then goes in and out of the cavity created. This behavior is always observed in both field and laboratory settings. “In terms of predators’ behavior, it’s interesting that ghost crabs show similar methods when they are uniformed and eaten in hatch mode,” Dr. Avenant noted.

More importantly, studies show that these crabs seem to foresee when the hatchery will appear. They often gather near the nest before turtles start to surface. This expectation highlights a complex strategy of plundering. Aquarium-based feeding experiments also confirmed crabs’ strong preference for animal meat, including tortoise eggs and incubators, rather than the usual brown algae diet, thus cementing their role as effective predators for early turtles.

Key research observations:

• Infrared video reveals detailed prey treatments for eggs and hatch.
• Ghost crabs often decapitate the hatch door by holding their neck and cutting with smaller claws.
• Crabs gather near the nest, seemingly foreseeing the emergence of hatching.
• Laboratory tests confirmed that ghost crabs prefer animal meat than algae.
• High-density ghost crabs can lead to widespread damage to the turtle clutch.

Impact on the survival of turtles

It was noticeable: On a beach with high populations of ghost crabs, multiple crabs can attack juveniles that emerge from the nest for several nights. This usually results in partial damage to the tortoise clutch and even a complete failure of nest hatching. “As an endangered species, high levels of eggs and hatches may be a long-term survival problem for the Loggerhead Turtle population,” explained Professor Glenn Hyndes, professor of coastal ecology at ECU.

Indeed, Dr. Avenant’s earlier research showed that more than 35% of Loggerhead eggs in Ningaloo nests were consumed by predators, and some individuals suffered 80% of sporadicity. Among the larvae that successfully appeared, nearly half (45%) subsequently precede.

The global challenge of turtles?

Ghost crabs are found on beaches around the globe, wherever turtles build nests. Although the study focuses on Australian golden ghost crabs, other ghost crab species also involve similar predation around the world. This study details specific feeding behaviors, including how crabs break eggshells and yield to hatch, which adds to observations targeting other ghost crab species elsewhere. The consistency of these predatory methods for these different species suggests that ghost crabs have a wider effective predation pattern in the early stages of fragile early life of turtles.

Understanding these specific predatory behaviors is essential for conservation efforts. How can protectionists better protect these tiny, fragile creatures from such persistent but often invisible threats?

In this new study, the use of infrared cameras has proven to be a powerful one

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