Travelling the world on Air Intestine (Image: Casper van Leeuwen)

NEED a lift? Get eaten by a duck. Some snails survive inside bird guts for hours at a time, travelling hundreds of kilometres before popping out the other end unscathed.

Intrigued by stories of live snails found in bird faeces, Casper van Leeuwen of the Netherlands Institute of Ecology in Wageningen fed four species of marine snail to mallards. Most died, but 1 per cent of Hydrobia ulvae snails survived up to 5 hours. Mallards can cover 300 kilometres in that time (PLoS One, DOI: 10.1371/journal.pone.0032292).

“Lots of birds eat tens of thousands of snails every day,” says Ryan Hechinger of the University of California at Santa Barbara. “Even if only a small fraction pass through, a substantial amount must be spread into new areas.” He has found genetic evidence to suggest that marine snails repeatedly travelled between the Pacific and the Atlantic after the isthmus of Panama had formed, possibly by hitching rides with birds.


Given the low survival rate, it’s probably not a deliberate strategy on the snails’ part, says van Leeuwen. “I don’t think the snail wants to be eaten. It just makes the best of a bad thing.”

It’s not just marine snails that travel the world on board Air Intestine. A recent study showed that 15 per cent of a Japanese land snail (Tornatellides boeningi) also survive being eaten by birds (Journal of Biogeography, DOI: 10.1111/j.1365-2699.2011. 02559.x). One snail even gave birth to young after emerging from its bird host.