How Invasive

On September 13, 2012 · Comments Off on How Invasive

I had a conversation recently with my friend the birder. He pointed out various bird species that happened to fly within line-of-site of our gathering, while noting which ones were native species and which ones were transplants. That led to discussions of various invasive animals introduced into North America either by accident or by design, and the havoc those alien encounters sometimes introduce.

I’ve talked about Zebra and Quagga Mussels in the Great Lakes before as well as Asian Carp in the Mississippi watershed. Those are good examples. Closer to home, we’ve had to deal with Snakehead fish and vicious Tiger Mosquitoes. Let’s not forget those ghastly primates, those homo sapiens either. They’ve been causing trouble everywhere.

We tend to think of ourselves in North America as the recipients of every other continents’ castaway pests. However, it’s not a simply one-way street. There are plenty of cute and cuddly North American animals that we’re used to seeing every day that have become a nuisance elsewhere, even pushing native species to the brink of extension in the most extreme instances.

Take for instance the prime example I used during my conversation:

Eastern Gray Squirrel

Gray Squirrel
SOURCE: Flickr via Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) license.

In the United Kingdom it’s spelled slightly differently, Grey Squirrel, and it’s become a major problem because it competes with the native Red Squirrel. The Global Invasive Species Database explains that "Eastern gray squirrels were introduced to Italy and England from the U.S., to Scotland from Canada and to South Africa and Ireland from England."

In the UK, grey squirrels have pushed native red squirrels northward. The cannot live within overlapping ranges because grey squirrels are larger, more competitive and voracious eaters. Grey Squirrels also have immunity to diseases they carry and subsequently spread to Red Squirrels with harmful results.

Groups in the UK such as the Red Squirrel Trust Wales and Cornwall Red Squirrel Project are attempting to push the clock backwards by reintroduce red squirrels into their previously-native habitat, for example:

The aim of the project is to re-introduce Britain’s native red squirrel into Cornwall. Red squirrels (Sciurus vulgaris) were common in England until the grey squirrel (Sciurus carolinensis) was first introduced to the UK from America as an ornamental species in 1876 and to Exeter in 1915. The spread of the grey squirrel was rapid, and in 36 years the species had reached Cornwall. The last of our native red squirrels was seen in Cornwall in 1984.

It’s hard to imagine the damage caused by these common mainstays of the eastern North American outdoors when exported elsewhere. I will note one more quote — completely irrelevant by the way — from the Invasive Species Database primarily for the benefit of all my relatives in Mississippi, "Grey squirrels (Sciurus carolinensis) are harvested for food in Mississippi (USA)." For the record, my family does not eat squirrels. Also I should note that squirrels are hunted in many different places, not just Mississippi (case in point). I don’t understand why the database singled-out Mississippi.

If we’re talking about animals more-or-less commonly eaten, perhaps we should also note:

Canada Goose

Canada Goose
SOURCE: Flickr via Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) license.

Wikipedia has a nice map of the Canada Goose range, including it’s non-native habitat. I wasn’t too surprised to see that they had been introduced to Europe. However they’ve surged in population in recent years. The Guardian focused attention on an emerging problem in France.

There are certainly so many of them in France that they are beginning to pose a threat to wetland biodiversity. The Canada goose is the largest goose found in Europe. It was introduced to Britain in the 17th century, then adopted as a game bird on the continent during the last century. In the wild they live 10 to 25 years and are prolific breeders. They are now resident in western Europe and, for reasons that remain obscure, their numbers have started increasing very fast. There were only several hundred Canada geese in France at the end of the 1990s. Now there are more than 5,000 spread over at least 58 départements, with half in the Paris area.

Canada Geese are also an issue on the other side of the world in New Zealand. NZ Birds traces their origin to "a gift from US President Theodore Roosevelt" in the early 20th Century and that "there are now so many of them they are sometimes regarded as a pest." Gee, thanks Teddy. He probably deserves to lose every race at Nationals baseball games simply because of that.

Birds are not the only creatures that have been transplanted from North America for the benefit of sportsmen.

Largemouth Bass

1351_largemouth bass (Micropterus salmoides)_300 dpi
SOURCE: Flickr via Attribution 2.0 Generic (CC BY 2.0) license.

The Largemouth Bass is a mainstay of anglers particularly in the southeastern United States where they are quite common. They are considered a great sports fish. Freshwater bodies literally around the world have been stocked with them as a result. Unfortunately Largemouth Bass are also extremely aggressive and hungry. They can destroy local native fish populations without much effort.

The Global Invasive Species Database includes Largemouth Bass too, and it notes:

Largemouth bass are highly adaptable fish, able to thrive in virtually every warm-water habitat, from small creeks to large rivers to huge reservoirs. About the only thing that limits them is cold annual water temperatures… Known introduced range: UK, Europe, Russia, Middle East, North Africa, Continental US, Caribbean territories, South America, Asia, Southeast Asia, Hawai‘i, Mauritius, Madagascar, Fiji, Guam, New Caledonia and the US Virgin Islands.

And the one I didn’t see coming.


Beavers Breakfast
SOURCE: Flickr via Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) license.

Beavers? Really? We even have beavers in an urban area boxed between an Interstate Highway and office towers near my home in Virginia (satellite view). Where could beavers cause a problem?

Beavers were released in Tierra del Fuego in a failed attempt to create a fur industry in 1946. Now, a little more than half a century later, the governments of Chile and Argentina are working desperately to stop their spread. Beavers are causing extensive damage to the local ecosystem, leaving a swatch of denuded forests and flooded fields in a destructive path pointed towards the north. This is all explained in an article in Nature, The Beavers Must Die. That’s the plan. They hope to eradicate the population permanently and with extreme prejudice.

I’m sure there are plenty of other examples. They are difficult to find because most of the information I could uncover related to invasive species coming into North America rather than moving the other way. Let me know if you have other favorites I haven’t mentioned.

On September 13, 2012 · Comments Off on How Invasive

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