It amazes me how man always puts the blame on an animal instead of himself.

I was surprised readinng the comments that so many people feel as I do: human beings are the problem, not feral cats. This article just gives people permission to be even more cruel to animals than we already are. I am not a Christian or anything else for that matter, but I am very familiar with the Bible and we should be stewards of this earth, not the primary destroyers. We have the judegement and ability to conrol our population, but the Smithsonian and other institutions that should be shouting out loud that there are too many people and we should do what we can to curb our numbers are doing nothing to get this message across. And they have all those researchers who make one mess after another trying to control nature in one way or another. First annhilate wolves, then reintroduce them, then start shooting them again. What happened to our intelligence and humanity? People need to spay or neuter their cats and dogs. It is that simple. If we did that, there wouldn't be feral cats and dogs who suffer pretty terrible lives. But I think that given the choice, they would choose to live, just as we would.

Man has been the cause of every problem in nature. For that matter in everything on Gods Green earth. Ive been sayin it for 30 years "There are just to many people"and yet world wide we continue to multiply into greater and greater numbers every day.

Photo#10 is a mongoose.Ohahu is covered with them.Introduced to rid the island of snakes.As far as invasive goes there are a lot of animals that aren't on the list,including humans.It depends on where you live,and how you define invasive.I'm over sixty,and I've seen a lot.I believe the earth will heal.The thing I like the best about all of the other animals,they don't have opinions.They don't pass judgements on each other,and they live within their environment.They don't try to change to suit their fancy.Wether you're a creationist or evolutionist man belongs here.I don't believe we came from outerspace.I'm a Christian and I believe we are part of God's plan.All of those"invasive" are too.I don't believe God sees them as invasive.

I am surprised that the virgina possusm,raccoon and the rock dove also known as pigeons. These animals had spread since the settlers had come from europe. As well the coyote from the west to the eastern part of United States.
I known about the feral cats killing wild bird populations as well,the domestic young duck,goose and turkeys. When I was a younger man. I had to help thin out the feral cat population on my cousin's and neighboring farms with my 22 long rifle.

I'm really not sure about your findings. Here in northern Wisconsin I've only seen where the more Red Squirrels you have the less Gray Squirrels you have.I've read where they actually do more damage than grays, by eating bird eggs, nesting in buildings, and actually chasing down grays when they come into their area. If I'm wrong let me know.

NUMBER ONE: Human Beings. I was really surprised you guys didn't know about this.

JERRY ANDREWS - I APPLAUD YOU!!! WELL STATED!!!!

I totally agree- the first guilty party here is the human race---mostly Europeans , their greed, arrogance and selfishness. there is no God that will fix this, we have to take care of the world ourselves. zMaybe we acn stop some of this, but I doubt it. Way too many humans are not in TOUCH with the earth. We are of the earth.

You really should have included Homo sapiens in this list.

Coyotes are overabundent here in New Your State. They have greatly reduced the deer herds by eating the fawns. There is a hunting season for them, but it doesn't seem to do much good so I guess the reproduction of coyotes is true. I don't think coyotes should be more welcome in the state than wolves who always get a bad rap due to the old stories.

The article probably ought to specify that specifically European rabbits are invasive in the Americas, given that there are plenty of native species.

We humans supposedly have the greater adaptive ability overall. An expression of that adaptive trait would be in recognizing our environmental role and impact. At least some can acknowledge the part we've played in the invasive species introductions that caused such ecological concern. Hopefully we are adaptive enough to come up with proper solutions to the mistakes made and lay a course correction wherever possible; and more importantly, let's hope we can learn from past mistakes and not continue to repeat them.

Very nice assortment of animals here and some interesting comments. As a devoted Christian, it is our responsibility to be good stewards of the gift that God has given us. Though I think the Lord will be coming soon, we have to keep our house clean until that day. Whether you want to consider humans as invasive or not, we have needs of the resources that are here, but we should not destroy our homes (ie, the environment outside my door which includes the whole earth). It is sickening to watch areas that are livable being destroyed by greed. In the last forty years or so, we have doubled from 3.5 billion people to 7 billion people. Everyone of them is or was someones darling baby (or grand baby). Let's manage the world so that all of God's children (those alive today and those coming in the future) can enjoy a wonderful world.

You left out humans.

I was surprised that coyotes were not on the list. Where I am in Georgia (north of Atlanta), we almost never see foxes anymore because coyotes seem to have taken over their territory.
Maybe coyotes are not considered invasive because, if left undisturbed, they simply fill in the predator niche that used to belong to wolves, bears, cougars, bobcat, etc.
Unfortunately, states like Georgia have no restrictions on their being hunted because they are not "native". Research has shown a disruption of a stable pack, speeds up their reproduction with more females having more pups (even producing litters in the fall) and the further extension of coyote territory. (Where I live that means more pets become prey. May-July when the coyote pups are weaned and needing fresh meat, there are lost pet signs posted everywhere.)
My fear is that unrestrained killing in my area, where coyotes tend to be much larger than out west, will lead to pack hunting behaviors that endanger larger animals and perhaps even children.

How much ignorance and arrogance does it take to write an article like this, and completely ignore human influence over each of the examples? Leaving aside the strong argument that we ought to be the first on this list, it's been our own botched attempts to manipulate and control our environment that have, in every case, led to these 'invasions' of other creatures. If we didn't deliberately introduce them, we killed off their natural predators.
What bothers me the most about this article is that it consistently describes these creatures as "disease carriers" and uses other derogatory language, as if somehow these animals are more unhealthy, or that 'scavenging' is an unnatural or obnoxious trait. These animals are behaving perfectly naturally - and disease is a natural phenomenon in all habitats.
This tendency we have to demonize things that seem to get in the way of our perfect plans, is not limited to our treatment of animals. We do it to ourselves. We need to find some humility, and take responsibility for our mistakes, which we make on an ever increasing scale.
These animals do not choose to 'exploit', to 'invade' or to 'destroy'. Those are human traits.

Definitely a mongoose; google its' scientific name. And definitely a good article; as someone who studied invasive species for a period of time, it is definitely a growing concern for the rest of native wildlife.

I think everyones comment is worth reading but are not all believable. I believe that God created the Earth for us to not only enjoy but to also spread to good news of Christ; not to be sitting around and complaining about how we are "ruining the earth" or that we need to "go green" and "save the environment." Animals may or may not be invasive; But i would definitely not classify humans as invasive because how could you be invasive on a world that was given to us by OUR Creator?? Thats just like saying that if you fill your house with all of your stuff you are being invasive.

Well I found this when my biology teacher asked us to read it and now I think I'm going to comment and see how much more interesting I can make this. ;D

First I want to know what defines an invasive specie? Well since I would have to post the get that question answerd I looked it up and found this: The first one in the list of three on wikipedia descibed it well (http://en.wikipedia.org/wiki/Invasive_species I would included it but its rather long)
Now if you look at my difinition it says,"Invasive Alien Species as those that are, firstly, outside their natural distribution area," So the obviuse question arises are humans out side of their natural distrubution area. The answer is no. Humans are (if you want to look at it this way) the top animal or mammal, we are at the top of the food chain, so it would make logical sense that if anything was to have the right to everything on the earth it would be us. It makes logical sense does it not?

Now lets look at the rest of the definition."and secondly, threaten biological diversity." Now looking at this I would say humans have had an efect on biological diversity in the past, but we are far from the worst mammal on the planet for it as clearly shown in this artical. And as our science and technoligy moves forward and upward we can only learn more about the environment we live in and how to be protect it

Yes, Humans do their fair share of damage and seem the most invasive to me. Someone asked what do you suggest we do about it? Birth control is one answer. but often humans prefer war. We have done our best over time to annihilate each other since time began. We may succeed one day. Then, the cockroaches will win the battle of the survival of the fittest.

Humans are not an invasive species. It all belongs to us. When we speak of "destroying the environment", we mean "making the environment uninhabitable for humans." There have been millions of years when the Earth was essentially a cinderblock, but Gaia was just as happy that way. The Earth doesn't care; we do.

There are no "invasive mammals." This a is a ridiculous moral judgement. Bravo for red deer, man, stoats for out-competing their rivals. It's called evolution. It's tough. Get used to it.

This is priceless. When I noticed there were comments to go along with this article, I wondered how long it would be before someone called humans an invasive mammal. And it was the very first comment!

One person's "invasive" is another person's "successful" I guess. You know, that whole survival of the fittest thing.

So what is your solution to this problem of invasive humans, LJ?

An island in the lower Columbia River was overrun with nutria. I led a move to offer a bounty for nutria. This has been quite successful in that thousands of 'nutria' were killed for the five dollar bounty. (Due to the success of the program, the bounty was recently raised to eight dollars.) The plague of nutria has been substantially reduced at very low cost; the total expenditure is still under $20,000--unlike the Chesapeake Bay multi-million dollar Federal nutria control program!

My respect for the Smithsonian has dropped considerably. How could you publish such an article without mentioning the most invasive and destructive mammal of all--the one that is also responsible for the spread of the invasive species you do mention. Humans!

I agree with LJ; this list should rank humans as number one invasive mammal.
Furthermore, humans are responsible, either directly or indirectly, for all these other species being "invasive". Through our catastrophic impact on the environment, on the natural balance of the ecosystem and by introducing non-native species, we are the ONLY ones to blame for these poor creatures' unwanted presence. What's even worse is that we create the problem, and then we stigmatise, pursue and eliminate these species - by any cruel means possible - whose only fault is to have demonstrated as much adaptive ingenuity as us.

Thank you for this excellent article drawing attention to a very important problem!

As a feral cat caregiver and active participant in Trap-Neuter-Release(TNR)program in my community, I am offended by your presentation of feral cats.

In my community as in many, feral cats are trapped, neutered/spayed, released, and maintained by colony caregivers. In the process, they are checked by a volunteer, licensed veterinarian for communicable diseases, are vaccinated, and have their ear clipped to identify them as being maintained.

Your article suggests to me that you are unaware of the very important worldwide movement concerning feral cats. Further, the caregivers to these colonies struggle everyday against the very falsehoods you are spreading in this very popular and far reaching magazine.

I myself have spent money on 300 pamphlets and numerous posters to educate my neighborhood about TNR and the importance of neutering and spaying the cats in both English and Spanish.

Shame on you for working against me and the other colony caregivers.

I vote for or against businesses with my money.

No. 10 looks like a picture of meerkats to me; it certainly is not mongoose.

And every one of these became invasive species because of human intervention. Human beings are the only invasive species that became so entirely by their own efforts.

How can you post an article about invasive species and miss the most invasive and damaging animal ever to inhabit the planet--the inaccurately named Homo sapiens? We consume, destroy & breed non-stop & have extended our life expectancy beyond all reason. We are a danger to all other life forms, ourselves included. If we disappeared, the natural world would swiftly rebalance & other invasive species would be reduced to an acceptable level within their new ecosystems, probably within less than a century.

Feral and domesticated cats are a major threat to birds as well as chameleons in my garden.Indiscriminate killers in my opinion. Based on what I have seen in my garden I would imagine they are a threat in the wild. Thanks for the article but I would agree with the above comment that habitat loss is our major challenge and with expanding human populations it will become even more of a problem.

The photo is NOT a mongoose!

When it comes right down to it, we humans have destroyed so much wildlife habitat that it's hard to imagine the imbalance in nature ever being corrected. We continue to detroy in the name of greed all over the world. Politicians always find a way to justify it (though the real motivation is the lobbyists' $ that line their pockets). I have to disagree with one post about feral cats. In my neighborhood, I have one of the few 'woods' that exist in the area. For 12 years I enjoyed visits from every species of wildlife in the area and literally 100's of species of birds (I provide shelter, food, water and play room for all). And then 2 years ago, along came an infestation of feral cats. Since then there is absolutely no wildlife and no birds who visit. The occasioinal chipmunk or bunny is quickly killed by the cats. They have killed at least 50 or so birds that I have witnessed. So, yes, they are pests. I've caught several of them and whisked them off to the pound (though I LOVE all animals; this just is not acceptable in the area surrounding my home). Each one I catch is replaced by another who finds his/her way to the wooded paradise that provides food and shelter in my yard. I'm tempted to buy a gun!!!!

Perhaps if more people would get rid of their manicured lawns and replace them with ground covers and seed/fruit/flower producing plants, trees and shrubs, we could restore SOME balance to the suburbs.

Actually, while possums might enjoy a meal of Eucalyptus in Australia, there are no native Eucalyptus species in New Zealand so there is no way possums could create an imbalance in the island forest vegetation by eating them. What they do threaten to wipe out are native trees like Metrosideros - the rata trees and the pohutukawa trees - and other palatable native species.

This article deserves a few points of correction.

Feral and stray cats are far from a recent phenomenon – outdoor cats have existed alongside people for thousands of years. That is unlikely to ever change. Numerous scientific studies show these cats to be on average just as healthy as pet cats. Rabies is, in fact, rare in cats – and unlike with canine rabies, no strain of rabies has ever evolved that is particular to cats.

Trap-Neuter-Return (TNR) – a humane program for feral cats gaining popularity across the country – makes cats even healthier by eliminating the strains of mating behavior and pregnancy. Most cats that are part of TNR programs are also vaccinated against rabies, providing an additional public health benefit.

Finally, when it comes to the true threats to bird, cats barely even rank. The chief culprit is the rampant suburban development of the last several decades, and associated problems like habitat loss, pollution and environmental degradation.

As animal advocates, we want what’s in the best interest of all animals, including birds. That means taking a hard look at what the major threats to species are and evaluating what we as humans can do to change the way our choices impact our environment Perpetuating myths about cats serves no beneficial purpose -- for cats, birds or for any other animal.

Elizabeth Parowski
Alley Cat Allies
Bethesda, Md.

As a Smithsonian subscriber, I'm disappointed in the lack of rigor represented in this article. There are plenty of free sources for pulp reading material based on rumor, guess and gut feel. I don't expect that sort of thing from Smithsonian and won't be renewing if you continue to publish such material. I suggest anyone interested in some well-researched facts about feral cats visit voxfelina.com and this article in particular: http://www.voxfelina.com/2010/12/on-invasion-and-persuasion/

You forgot the number one invasive mammal. Humans! Also, we are often responsible for these animals leaving their original habitat in the first place.