Watching baby turtles hatch on a tropical beach is on many people’s bucket list, although while the experience may be hugely uplifting for tourists and wildlife enthusiasts, it’s extremely arduous and perilous for the turtles themselves – something which may well be exacerbated by the presence of humans, according to a new study.
The first moments of a sea turtle’s life are among its toughest, as it breaks free from its egg buried in the sand, scrambles to the surface and drags itself to the water while trying to avoid getting eaten by birds, crabs, and other predators. Nature at its harshest, this highly dangerous rite of passage is survived by few hatchlings, only one percent of which live to sexual maturity.
In the face of such low success rates, it’s highly important that the infant turtles are given the best possible chance of surviving this journey to the sea if population numbers are to be sustained, although new research indicates that artificial light may be hindering their prospects.
Study co-author Charitha Pattiaratchi explained in a statement that “it is widely known that artificial lighting near turtle nesting beaches attracts turtle hatchlings as they emerge from nests and can cause them to have trouble finding the sea.” However, little research has been conducted into just how disruptive man-made lights are to these hatchlings.
To investigate, the team tagged 40 green turtle (Chelonia mydas) hatchlings with miniature acoustic transmitters, before releasing them in the waters off Wobiri Beach in Western Australia. The turtles were released shortly after moon-set, a time when no natural light appears in the sky for them to follow.
A green turtle hatchling models the tracking device. Thums et al Royal Society Open Science
Half of the turtles were released under ambient conditions, while the other half were released in the presence of a 400-Watt light, which was shone onto the surface of the water from the side of the boat. When tracking the turtles’ movement, the researchers found that those released under ambient conditions all followed a very similar path, headed north-northwest.
However, 88 percent of those released in the presence of the artificial light headed directly towards the source of the glow, apparently mistaking it for the Moon. As such, these turtles took considerably longer to exit the near-shore area, which is where the greatest threat of being caught by predators exists.
Summarizing their findings, which appear in the journal Royal Society Open Science, the researchers write that “this is the first experimental evidence that wild turtle hatchlings are attracted to artificial light after entering the ocean, a behavior that is likely to subject them to greater risk of predation.”