Sunday, January 30, 2011

Florida Snails

If you are amongst the myriad birders that migrate south to Florida to gawk over some of the Sunshine State's specialty birds, you must thank snails. But all is not well in the world of these univalved gastropods, as we shall see.

Windrows of apple snail shells litter the edge of a Florida marsh. I believe that all of these shells are of the introduced Island Apple Snail, Pomacea insularum. This invader, native to South America, has colonized much of peninsular Florida and can be locally abundant.

High on any birder's Florida wish list is the spectacular and aptly named Snail Kite, Rostrhamus sociabilis. This female has an apple snail in her mandibles. Snail Kites have an incredibly long tip to the upper mandible of the bill, and their slender bill has evolved to harvest snails from their hard shells. But not just any snail - Florida Apple Snails, Pomacea paludosa. Unfortunately for the kite - and the snail - Florida's only native apple snail is under siege from at least three threats: outright destruction of wetland habitats; alteration of water regimes in existing wetlands; and the invasion of four other non-native species of apple snails.

These invading snails displace the native apple snail, and it appears that young kites have a much tougher time extracting the meat from the larger and bulkier introduced species.
If the kites, which feed almost exclusively on apple snails, can't make the jump to the non-native snails, their prospects in Florida do not appear good.

Another wonderful Florida bird for U.S. birders is the Limpkin. What it lacks in plumage pizazz is more than made up for with earsplittingly loud piercing cries. Interestingly, this bird's range nearly mirrrors that of the Snail Kite, with Florida being the northernmost outpost. Like the kite, Limpkins are major snail consumers. As might be geussed from the size of their giant crowbar of a bill, Limpkins apparently can readily handle the enormous invader apple snails and seem to be thriving. I must have seen or heard a few hundred Limpkins in my short five days in Florida, including one favored spot where at least 65 were on display at once.

At a secluded hardwood hammock deep in the Everglades, I was delighted to see a number of Florida Tree Snails, Liguus fasciatus. These often colorful arboreal snails have become rare, and are now listed as a species of special concern by the state of Florida.

Showy and easily harvested, Florida Tree Snails are much sought by collectors, who have diminished or eliminated the snail's populations in some areas.

There are eight described subspecies of Florida Tree Snail, and they come in a dazzling variety of color forms. This one was my favorite of those that I saw.

Florida Tree Snails enter a period of aestivation, or dormancy, in December. They scale the trunks of smooth-barked trees, and once a favorable spot is found secure themselves tightly to the tree by forming an airtight, cementlike bond at the shell opening. As the snails often select eye-level resting locales they're easily noticed.

At least 58 color varieties of Florida tree Snail have been noted, and some of them are incredibly showy; Gastropodian gems of dazzling ornateness. Greedy collectors have killed off some of these forms, and any Florida Tree Snail, whether it be a Plain Jane or rainbow of color, should be left unmolested.


Vincent Lucas said...

Glad you had a chance to see some of our gastropods when you were down here Jim. Yes, the exotic Apple Snails are a problem for juvie Snail Kites and I rarely find the indigenous Apple Snail any more when I'm out in the field. This year has been a phenomenal year for Limpkins, due in part probably to the abundance of their favorite food. The Liguus tree snails are way cool and I always delight in seeing them. You can find out more info/ID's, etc. here:

Jim McCormac said...

Thanks for the info, Vince, and for showing me lots of cool birds and interesting areas down there!

jan godown annino said...

from fl -
this is an excellent report. my hubby & i found it while looking up/reading up on fl snails mentioned in
a short story for children (fiction.)

so - want to mention how helpful it is.