Tilly the sea turtle already knew about the Tonga eruption before it happened

Ten weeks ago, two green sea turtles were released off the Australian coast fitted with satellite transmitters. One of the two immediately headed east and stayed on course for 47 days, heading for the Tonga Islands. But suddenly, she made a 180° turn as if to avoid the place. The next day, the Hunga Tonga-Hunga Ha’apai volcano erupted, triggering the tsunami and ash rain that devastated nearby islands.

According to Jennifer Gilbert of the Cairns Turtle Rehabilitation Center (CTRC), it is “speculative” to state that Tilly knew what was about to happen. However, his itinerary does not appear to be a coincidence. Also, as the turtle returned to the Great Barrier Reef, a small earthquake hit northern Queensland. This small earthquake did not cause major damage, but the event coincided with Tilly changing course again.

Gilbert indicated that she now wanted to write an observational article on the subject. Indeed, turtles have never been the subject of seismic detection studies. This ability had already been studied in whales, dolphins, seals and even goats.

Tilly’s story

Tilly’s life didn’t start out like any other sea turtle. When volunteers checked the nest where Tilly was, they noticed that the majority of the eggs had not hatched. And deep in the nest, two little green turtles were struggling to get out. So we decided to help them and bring them to the CTRC.

The two turtles were named Tilly and Sammy, although the gender of the green sea turtles cannot be identified until they are 20 years old. According to Gilbert, it was unclear at first if the two animals would survive, but Tilly and Sammy managed to thrive.

Typically, rescued turtles are released when they reach a size of 45 centimeters, but due to Covid-19, travel to the continental shelf where they were to be released was not possible. The turtles were then only released when they were three years old. CTRC researchers were able to fit them with more powerful trackers.

The CTRC team was amazed to see that Tilly was able to cover almost 3000 km in 73 days. As for Sammy, his tracker stopped working just 10 days after his release. This damage could have been caused by a malfunction of the aircraft or by a bad encounter with a shark.

An unexpected route

In any case, the researchers were surprised that a 3-year-old turtle was heading straight for deep waters thousands of miles away, apparently in search of reefs, rather than the Great Barrier Reef, much more practical. According to Gilbert, these waters are full of predators, and Tilly was certainly heading for the Solomon Islands or New Caledonia without anyone knowing why.

The CTRC had no other turtle trackers in the area at the time, nor did the other Australian research institutes. It is therefore unknown whether other turtles had also avoided the Tonga volcano.


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