Faucet Snail Kills Wisconsin Water Fowl

The United States Geological Survey reports that a non-native snail, imported to the Great Lakes Region from Europe in the 1870s, where it is well distributed, is causing worrisome water fowl deaths at Lake Onalaska, near the upper Mississippi River, near La Crosse, Wisconsin.

The snail was first introduced into the Great Lakes. It has now made its way west.

The snail causes problems only when it carries one or two trematode parasites, worms commonly called flukes, called by the scientific names Cyathocotyle bushiiensis and Sphaeridiotrema globulus. The snail itself has the common name of Faucet snail.

Waterfowl typically eat snails, and if they eat an infected snail, they are likely to die. This is of special concern because the snails are now found within the Mississippi Flyway, sort of a bird hub airport, through which forty percent of the continent's fowl migrate.

Birds affected are lesser scaup, American coots, northern pintail, wigeon, northern shoveler, blue-winged teal, mallard, American black duck, gadweall, redhead, ring-necked duck, bufflehead, tundra swan, herring gull and ruddy duck.

At its worst, birds can die within a week of eating infected snails, which tend to like the underwater rocks near islands, but can inhabit other parts of lakes and ponds.

There is concern that because the snails are located in the Flyway, infected birds could somehow spread the snails to other areas. Studies are underway to determine what areas are infected. It is difficult, sometimes, to tell if a bird ate the snails locally, or if it ate the snails at a remote location and flew to the area where it eventually died.

The USGS finds that it has to spend more human hours doing research and outreach because of this new threat.

Another worry is that hunters might be inadvertently collecting the infected birds. When a hunting dog comes across a bird dead from infection, rather than from gun shot, it sometimes retrieves the infected bird instead. Anyone consuming the bird might be at some health risk.

Water bird populations are on the decline, and Faucet Snails and their parasites may help account for part, if not all, of the die off. The greater and lesser Scaup population was 37 percent below its average last year, for example, and other bird populations are on the decline.

Non-native species can be imported into an area through natural migration; they can be introduced by humans, sometimes on purpose, sometimes inadvertently, for example, when aquarium snails are dumped into lakes or ponds; global warming can account for some warm weather species migrating into new areas, for example, the spread of Killer Bees from South America. Killer Bees were introduced into South America from Africa by a scientist.

Exactly how the snails spread from the Great Lakes to the Lake Onalaska area is unknown.

Source: local reporting
Source: Sauer, Jennifer, and Rebecca Cole and James Nissen, Finding Exotic Faucet Snail, USGS