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Posted by Larry Connor on 10:15:01 03/20/08
In Reply to: snails for kites and limpkins posted by Cindy McIntyre
That is an egg mass of the non-native island applesnail (Pomacea insularum). Island applesnails were introduced in Florida in the 1980's most likely as escapees or releases by the aquarium industry. The first records are from canals south of Lake Okeechobee in 1987. Since then they have expanded their range to include generally all of Peninsular Florida, the Tallahassee area, and some locations in South Georgia either by new introductions, movement by birds or other animals, hitchhiking on water craft, flood events, etc. Their presence was basically under-the-radar until the early 2000s when the FWC and the DEP began getting numerous reports.
I have talked to the park manager at Green Cay and who suspects, but cannot prove, that the n non-native snails were intentionally introduced in the wetlands. We have a couple of other suspected intentional releases. First, releasing non-native species in Florida is illegal. Second, introducing a non-native species may have severe consequences for the environment. Unfortunately, this is usually not predictable beforehand. Island applesnails and the closely related channeled applesnail (P. canaliculata) have caused problems in the environment and are considered a major pest in agriculture in Hawaii and Southeast Asia. The FWC, DEP, and Florida Department of Agriculture and Consumer Services are extremely concerned about the spread of the non-native applesnails. These species feed on rooted aquatic vegetation unlike the native Florida applesnail (P. paludosa) that feeds on algae. The non-native applesnails have been implicated in the loss of aquatic vegetation in a number of lakes in Florida, but there are, to the best of my knowledge, no studies that solely attribute damage to the snails. The FWC and DEP are sponsoring research to assess these potential effects and potential competition with the native applesnail.
There is some anecdotal evidence that limpkin populations increase where island applesnails are found. Again there are no documented studies that I am aware of that address this. One of the initial concerns was how the non-native snails would impact snail kites. Snail kite's talon and beak anatomy is adapted to capturing and consuming Florida applesnails. The island applesnail is much larger and heavier than the Florida applesnail. Darby et al. just published a paper in Florida Field Naturalist that found that snail kites dropped 44% of the island applesnails they captured versus 0-1% of the Florida applesnails. They also took about 3.5 times longer to extract the snail once they successfully returned to their perch. Darby felt that this could be a problem especially for inexperienced, juvenile kites; however, the inefficiency of capturing and consuming the island applesnails might be offset by the snails larger size. The jury is still out and, like we scientists say many times, further research is indicated.
Currently there is no effective control method for the non-native applesnails. There is ongoing research on some promising methods. The most effective method we have now is to remove the egg masses and physically destroy them. We used to recommend scraping the eggs into the water and allowing them to drown, but this is only about 80% effective. Both of these are obviously very labor intensive and not suited to a water body like Lake Toho for example. The upshot is please DO NOT intentionally introduce the non-native snails in new water bodies. Be sure that you clean your boat and trailer before moving it between an infested water body and a clean one to avoid transporting snails and other invasive aquatic vegetation like hydrilla. You can help by destroying any non-native applesnail egg masses you find. Check out our hand out and reporting information on the link below.
Thanks,
Larry Connor
Exotic Species Coordination Section
Fish and Wildlife Conservation Commission
Eustis, FL
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