Once these snails come out the other end, I doubt they’re ever the same.
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.”
via New Scientist