Monday, April 09, 2007
Cross The Pond
The Minnesota Department of Natural Resources has a request for their state's constituents: stop stocking your outdoor ponds with American bullfrog tadpoles. The American bullfrog (Rana catesbeiana), while native to the US, are only considered native in the far southeast part of Minnesota.
Recent surveys have shown new naturalized bullfrog populations showing up all over the state. Part of the reason for this is likely that pet shops, nurseries and other sources for water gardening supplies are selling the tadpoles illegally. Though the darn things can still be sold legally, without a permit, for bait, which doesn't make sense to me given this dire-sounding press release.
Labels: amphibians, animals, frogs, Minnesota
It's a very good point that those things we think of as "native" have no overall nationalistic urges, and may not be native to parts of a country in which they are not normally found.
I recall the western US as a particularly sensitive area to bullfrog importation, and it seems Utah was a focus. Loosed bullfrogs are having an impact on what few isolated and unique species of frogs Utah has. Reminds me of the invasion of the "native" O. rustica species of crayfish into areas where it did not before exist - courtesy of fishermen who lose their O. rustica bait.
Bullfrogs are native here in the southeast, but are a part of the succession of frog communities. You might have a myriad species of treefrogs, leopard frogs, chorus and cricket frogs, but once the bullfrogs move in, all those decline.
As a "water gardener" myself - we have a small goldfish pond - I suspect at least some of the introductions may be accidental. When you purchase something like a water lily you get a quart or so of water along with it, and who knows what might come along for the ride. Perhaps it would be possible to develop a chemical treatment to kill unwanted animal life in the "take home" container without killing the plants.
I'm wondering...given the odds that climate change is in fact in process as we speak, and that native species migrate at rates well below the projected changes, don't we squarely face widespread local species extinctions?
For instance, if hemlocks project to survive only above Maine, and I like them and all they support, don't I want to send seeds northward, now? Tree species migrate, what, ten miles a century, on average? No way they will move far enough fast enough to outpace any modelling I've seen.
Bullfrogs migrate faster than trees, I suppose, especially if man is involved. But given the changes coming, bullfrogs will be moving northward soon anyway. They may already be.
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