How Snails Cross Vast Oceans
There have been surprisingly few experimental efforts to explore the possible avenues by which Hawai‘i’s snails might have crossed oceans to arrive in their new home. In fact, to date there has been precisely one study on this topic of which I am aware. In 2006, Brenden Holland, a researcher in the biology department at Hawai‘i Pacific University, placed a piece of tree bark with 12 live snails of the species Succinea caduca into a saltwater aquarium. This is one of Hawai‘i’s nonendangered snail species; in fact, it is one of the few species that is found on multiple islands and seems to be doing okay. It is a coastal species, and the individuals enrolled into the study were from populations living as little as 10 meters from the beach. Brenden explained to me: “After heavy rain, they are commonly seen in gullies by the coast so there’s no question that they are going to get washed down pretty frequently.”
The purpose of Brenden’s experiment was to determine whether, when this happens, it might be possible for these snails to move around by sea and successfully establish themselves in new places. The answer, it seems, is yes. Brenden and his colleague Rob Cowie reported that: “After 12 h of immersion, all specimens were alive, indicating that sea water is not immediately lethal and suggesting the potential for rafting between islands on logs and vegetation.”
It is possible that land snails are floating around the world to distant places.
Why, you might wonder, does this matter? Far from being an abstract, albeit fascinating, scientific curiosity, I am convinced that attending to snail biogeography and evolution is particularly important at our present juncture. Hawai‘i was once home to one of the most diverse assemblages of land snails found anywhere on the planet, over 750 species. Today, however, the vast majority of these species are extinct, and most of those that remain are headed, my hope is that paying attention to the deep-time processes of snail movement that brought them all here in the first place could help us to understand and appreciate these snails in new ways. As the writer Robert Macfarlane has , a deep time perspective can offer “a means not of escaping our troubled present, but rather of re-imagining it; countermanding its quick greeds and furies with older, slower stories of making and unmaking.”
