Researchers studying feces of wild Japanese white-eye birds had noticed a surprising number of intact snail shells, especially of Tornatellides boeningi. This 0.1-inch (0.25-centimeter) snail is common to Hahajima Island (see map), about 620 miles (a thousand kilometers) south of Tokyo.

So Shinichiro Wada, a graduate student at Tohoku University in Japan, and colleagues fed more than a hundred snails to captive white-eyes and 55 to captive brown-eared bulbuls, another bird known to eat T. boeningi.

The team found that roughly 15 percent of the snails passed through both bird species' guts alive. One snail even gave birth shortly after emerging—apparently unfazed by its incredible journey.

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