Tiny computers mounted on snail shells helped reveal how one species escaped extinction

Thanks to tiny computers mounted on the backs of snail shells in Tahiti, scientists have discovered how one species survived extinction while others fell prey to an invasive carnivorous snail, according to a new study. 

The rosy wolf snail was introduced to the island in the 1970s as a way of controlling another invasive species, the giant African land snail. But the rosy wolf went on to prey on indigenous tree snails and wiped out more than 50 species.

"They would use their sharp teeth on their tongue, and they would basically kind of eat away at the soft tissue — so rasping away. The other way that it does it is, it would just swallow a snail whole, shell and all," ecologist and evolutionary biologist Cindy Bick told As It Happens guest host Duncan McCue.

But the white-shelled Partula hyalina snail survived, although the population remains precarious. Bick found that several factors, including their high reproduction rate, helped to improve their survival rate, but that still didn't explain why other snails with similar reproduction rates died off.

The researchers theorized that snail shell colours contribute to the amount of light they can tolerate, which would give white-shelled snails a biological advantage against predators with darker shells and therefore, a lower tolerance to light.

The snails that can endure light would be able to be out during sunlight hours, while the predating rosy wolf snails were likely to avoid the sun. 

In order to test the theory, Bick turned to technology to help track the solar intake of rosy wolf snails compared to Partula hyalina.

Bick, and other researchers from the University of Michigan, attached tiny computers, measuring 2 by 2 by 4 millimetres, onto shells of rosy wolf snails. They also put computers on leaves harbouring Partula hyalina, instead of on the snails directly, because they're a protected species.

"We're talking about a snail that is about the size of the tip of your finger. So you want to make a computer that small so that you can attach it to the shell of the snail. So that's the first thing. Second thing that you would probably want to do is make sure it sticks." Bick said.

Using biodegradable glue, the researchers attached the devices and began monitoring the solar data.

The team found that the Partula hyalina are able to absorb higher levels of solar radiation than the rosy wolf snail. They published the study last month in Communications Biology.

"Think of it as like hiding in plain sight, hiding in the sun. And think of the Euglandina rosea (rosy wolf snails) as a vampire. It can't really come out during the day, or it's very limited during the day. But then at night, all bets are off," she said.

To Bick, this was a story of resiliency.

"This is a story that tells us something about, what does it take to survive, especially with climate change, habitat degradation ... or the introduction of invasive species," she said.

"If we are proactive about conserving, or taking measures to preserve, some of these environments in which some of these species can survive, they are able to hang on a little bit longer."

Written by Mehek Mazhar. Interview with Cindy Bick produced by Niza Lyapa Nondo.