July 11, 2011

Small Snails Can Survive Bird Digestion

According to scientists, snails are able to survive intact after being eaten by birds.

Researchers found that 15 percent of the snails eaten survived digestion and were found alive in the birds' droppings.

The evidence suggests that bird predation could be a key factor into how snail populations spread.

Japanese researchers from Tohoku University investigated whether invertebrates could also spread in this way.

Previous research has shown that pond snails can survive being eaten by fish but the same was not known for land snails.

Studies of the diets of birds on the island of Hahajima identified the Japanese white-eye's preferences for the land snail.

Scientists fed the birds with the snails in the lab to find out whether any survived the digestive process.

"We were surprised that a high rate, about 15 percent, of snails were still alive after passing through the gut of [the] birds," researcher Shinichiro Wada said in a statement.

The team also studied the genetic differences of T. boeningi populations found across the island and discovered considerable variation.

Rather than only mating with nearby snails, these results show that different populations made contact despite their geographical distance.

"Biogeography of wingless terrestrial invertebrates, in particular snails, is often faced with mysterious long distance dispersal patterns that can only be explained by hand waving arguments involving birds' feet or guts or cyclones," Wada said in a statement.

"This is the first study showing that birds can indeed transport a substantial [number of] micro land snails in their gut alive."

One snail helped researchers identify how numerous snails could travel over distances through bird droppings.

"One of the snails fed to the bird gave birth to juveniles just after passing through the gut," Wada told the BBC.

According to scientists, the main factor allowing the snails to survive being eaten is their small size.

The micro snails fared much better than larger species in previous studies whose shells were severely damaged when eaten by birds.

The team said further study is required to find out whether the tiny snails have other adaptations that allow them to survive.


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