We all know that there are animals that have managed to make their way into places they did not belong. The question for many is, how did they get there? Most of the time, this had to do with them being introduced by humans to the environment. It might be due to a purpose-driven mission by a person or group. Other times, it was completely by accident. Either way, the most notable invasive species on the planet have caused several, often severe consequences to ecosystems.
For our list, we decided to focus strictly on animal species and not plants, fungus, or anything else. That’s for another list, at another time. This list will focus specifically on animals that have become major problems to ecosystems worldwide. Many are invasive on land, while others are invasive in the ocean. No matter what, we’ll be discussing where they are originally from and how they managed to invade other territories around the world. That said, let’s get started!
Invading:Lands Throughout Europe, North/South America, Asia, & Australia
When you see the name “European Rabbit,” you naturally assume it’s a rabbit native to the European continent. Great job putting those two together, Sherlock. However, the main issue with this rabbit is that it has been invading areas outside its normal realm in both Europe, the Americas, Asia, and even Australia. It is native to the Iberian Peninsula, where it had thrived for hundreds of years. Like most rabbits, the European model is known for reproducing heavily.
As a result, it has managed to become one of the most notable invasive species. They are now on every single continent worldwide, with the exception of Antarctica. In almost all cases, the rabbit was introduced by humans into the environment. The initial idea of increasing the food supply. Yet things got way out of hand. In Australia, they do not have any specific natural predators, which has caused the population to skyrocket and affect the overall ecosystem of the continent.
The Japanese Giant Hornet, also known as the Asian Giant Hornet, was perfectly fine originally. Although a terror to all insects around it, the species was only native to one territory. The species is located across Asia for the most part. Obviously, Japan is the primary place to see them. Yet they were somehow able to get on a ship that was destined for the United States of America.
As a result, it flew off of the ship upon arrival. This allowed it to become one of the most notable invasive species in the country. The hornet began terrorizing other insects in the area, throwing off the entire ecosystem that never had to deal with hornets like this before. While they fight with bees a lot in Asia, those bees know how to handle them for the most part. The American bees were unable to adapt, causing a surge of bee deaths that cut the population down far too much.
Cicadas can be found all over the world, and they can be pretty useful in various environments. Either as food for other animals or help to cut down other mass insect populations. However, while they are native to many areas, some are not. There is a specific species of cicada known as “periodical cicadas.” They actually remain underground for quite a long time and only emerge every 13 to 17 years.
As a result, they’ll mix it up with other cicadas already present and help to make the population higher. That increase makes them a notable invasive species, due to ecosystems not being prepared for decade-long absences. Cicadas are important to the environment, but only when the species is in a steady position. This specific line in their species pool is incredibly invasive and only serves to hurt ecosystems worldwide when they sprout up.
Invading:Australia, Phillippines, New Zealand, United States
Tilapia, as a species, is quite massive. There are a ton of them, and they are relatively worldwide at this point. Due to the massive population, some versions of the species have affected ecosystems in many regions. They are mostly freshwater fish, so unlike some fish that move around due to climate change, tilapia almost certainly popped up elsewhere due to humans. Tilapia can live in saltwater too, which is why they have been introduced in some places like Australia within that sector.
They take away valuable food that other fish were getting previously, which brings those populations down. Due to the fact that they are a notable invasive species, fishing for tilapia is a major industry. It is the 4th most consumed fish in the United States, where it’s incredibly invasive. The idea is that fishing at specific times of the year will reduce the population in those regions it has become a pest. This has actually helped too.
Invading:Hawaii, Fiji, Jamaica, Cuba, Trinidad, Puerto Rico, Hispanola, Japan
Most of the time, people know of mongoose due to seeing them battle it out with snakes, especially in parts of Asia. However, they are not native to other places they have been spotted in. Specifically, the Small Indian Mongoose is literally native to one region of the world. They have popped up a lot in the Caribbean and Pacific Islands, introduced by humans for one reason or another. In Jamaica, for example, they were brought in to help reduce the black rat population running rampant there.
The rats affected sugarcane production, which was big business in the region for centuries. Adding the mongoose could reduce the rats and it did help slightly. However, the same method was used in Hawaii, Fiji, Cuba, Trinidad, Puerto Rico, the Virgin Islands, Hispanola, and even Japan. The issue with this is that the species reproduced within months and eventually became pests to these regions themselves. Making them one of the most notable invasive species on the planet.
The Red Fox is likely the most well-known of all fox species and is likely the one you think of when you think about “the fox.” They are native to many areas around the world, such as most areas of North America, Asia, Europe, and Africa where they have lived for centuries. Yet they were actually introduced to Australia around the 1800s, with one reason supposedly being to help control the pest population in specific regions.
However, foxes are impressive carnivorous ambush predators who can take down pretty much anything smaller than themselves. That has led to the red fox becoming one of the most notable invasive species to Australia, where it has reduced mammal and bird populations. Some species within the bettong & wallaby family have been reduced due to the red fox specifically. There are now over 7 million red foxes at the bare minimum across Australia, which is pretty insane.
If you live in North America, it is almost 100% likely you’ve seen or come across a yellow jacket at one point or another. They are all over the place, especially in the Southern United States. However, some have become native elsewhere. While the species mostly lived in the Americas and Europe, they somehow have managed to establish themselves in Southern Africa. It is assumed that they could have gotten there on their own.
However, they were more than likely introduced to places like Australia and New Zealand. They have become pretty major pests there in recent years. However, if you want to talk about notable invasive species, we cannot forget that yellow jackets nest wherever. This has led to many establishing nests at human dwellings. You might see them underneath porches, in an attic, garage, carport, you name it. The little guys are freakin everywhere!
Invading:Australia, New Zealand, England, Ireland, Scotland, Brazil, USA, Cuba, etc.
The Feral Goat species is widespread worldwide, and this is exclusively due to human introduction. They were introduced in England, Ireland, Scotland, Wales, New Zealand, Brazil, Panama, Madagascar, New Guinea, Cuba, Honduras, Lebanon, Australia, and the United States. Of course, they were even introduced to the Spanish island of Majorca too. It is hard to know where the species originated.
However, many believe it was in Asia due to so many areas in Europe only seeing them as of 4,000 years ago. It is believed modern-day Iran is the main place they are from, as they were first domesticated there beginning 10,000 years ago. They were useful in removing unwanted vegetation, with some being able to produce milk. On top of that, they could be a useful food source. Yet the species ended up breeding like crazy, causing a massive spike in the feral goat population worldwide.
The story goes that shortly after World War II, a few brown tree snakes somehow was able to stowaway in transporting cargo from the South Pacific to Guam. The species is native to the South Pacific territory, so when the ship or possibly aircraft made its way to Guam, the snakes got off. They would then become major pests to the environment. In fact, they are specifically the reason for many native bird populations being drastically reduced in the region.
They also become top predators, which then reduced the population of other predators in the region due to a lack of food resources. Feral pigs and mangrove monitors were specifically affected by this. Guam is a major delivery hub in the region, causing the brown tree snake to stow away in cargo and land in more places. Including Hawaii, Japan, and mainland North America. Due to being so widespread, they are one of the most notable invasive species on the planet.
Invading:North America, Australia, New Zealand, South Africa, Caribbean Islands, etc.
The European Starling has managed to get around. They are now widespread and can be found pretty much all over the world outside of arctic regions. They were mostly found in the United Kingdom territories but were eventually introduced to other places. This includes North America, Australia, New Zealand, South Africa, Fiji, and many Caribbean Islands. This is a bird obviously, and thus, can fly.
Due to this, some were able to migrate to other areas near the places they were introduced by humans. That includes Thailand, Southeast Asia, and New Guinea. The bird species is a problem for both humans and other animals alike. They enjoy fruit, as do many. With so many being present, as well as their ability to fly, they have reduced fruits and even some vegetables that grow in the wild. They also get into human crops. Overall, they are a notable invasive species that needs to be reduced.
Cane Toads are quite interesting creatures. While they can make humans a little sick, they are capable of killing other animal species. This is due to its poison glands, which makes many predators think twice about attacking them in the wild. Of course, this makes them a bigger problem for domestic dogs, who might grab one randomly. Which ends up killing the dog, sadly. It’s sort of odd how the cane toad became such a notable invasive species.
We know humans introduced them to several Pacific & Caribbean Island territories as well as Australia. However, this was done to control pest populations in the area. These areas are known for some pretty terrible insects, which the cane toad helps to reduce. The use of them in these areas was pretty successful, but they are now pests themselves. Apparently, at the time, humans did not realize how impressive the species was at breeding. Now, these places are seeing the toads in mass amounts.
When most people think of Elk, they naturally assume that they’re in colder environments often surrounded by snow. While Elk do thrive in those areas, they are actually capable of thriving in warmer and even humid environments too. The species is found all over the world for a reason. However, they are actually not native to most of South America. Yet the Argentian government felt the species could be a great addition to their ecosystem for multiple reasons.
They felt the Elk would provide a great hunting experience while also offering meat for families to eat. On top of this, their hide could be used for clothing or sold, as well as its antlers. The elk managed to adapt perfectly to the environment, but this was not exactly good. Elk are terrific at breeding and are great at defending themselves against potential predators or competitors. This has caused them to take over the nation’s ecosystem, where it competes for food with the Chilean Huemul and other herbivores. Causing some of these populations to reduce while the elk population rises.
While many likely have no idea what a Nutria is, the species is pretty common around the world. It is a herbivore, so it does not generally compete for food with large predators or humans. Of course, this is a semiaquatic rodent. They can get pretty large, even bigger than the average beaver. You’ll normally only see them in or around burrows it has made alongside stretches of water. This is due to it feeding on nearby plants there.
They are originally from South America but were eventually introduced to North America, Europe, Asia, and Africa. This is mostly due to the prized fur the creature has. It can be used for clothing, and offers a small bit of waterproofness, making it a great asset. However, it is now one of the world’s most notable invasive species. This is due to the destructive burrowing and the fact that it now commonly comes in contact with humans. This partly due to continued construction, but still.
Native To:Possibly Asia or Africa (They Were Domesticated 15,000 Years Ago)
When we reference “wild dogs” in this section, we do not mean the specific species of “Wild Dogs” native to Africa. Rather, it is a large label for all regular dog types in the wild. Of course, most dog types these days are domesticated. The problem is that some are forced to live in the wild due to the lack of a human home. More often than not, dogs will find packs to congregate with due to the large population of dogs literally all over the planet.
Wild dogs will often mate with domesticated dogs or other canine species. This involves wolves, coyotes, and even Australia’s dingo species. In fact, Australian animal experts claim that there are now more Dingo-Dog Hybrids living there than purebred dingos. This is 100% to do with wild dog populations. Of course, dogs eat meat and will compete with many animals and even canine species for food. That has caused dogs to become a notable invasive species all over, especially across North America & Asia.
There is a big reason that Largemouth Bass fishing is a major thing in the United States. The population can get out of control, so we fish to control their population as best we can. It’s most common in the Southern U.S., where this freshwater fish is found in abundance. Bass are known for breeding very well, so they could affect an ecosystem drastically. Of course, we might know this but many places this bass was introduced did not realize its power. Bass can do some pretty incredible things.
They are capable of “trophic plasticity.” This means they can adjust their feeding based on only the energy they need. Allowing them to adapt to new environments. Thus, introducing them to other places was easy. Bass has been introduced to the Iberian Peninsula, parts of Canada, and Japan. In each one, they were wildly successful at the cost of other fish species. Many blame them for the extinction of the Atitlan Grebe, and they have reduced the fish population in Japan since 1996.
Invading:North America, Australia, New Zealand, Caribbean Islands, & Several Asian Countries
It should not be shocking that a species literally called the Red “Imported” Fire Ant is not from a region it happens to be terrorizing. Of course, the first time the ant was introduced to a new area, it was by accident. Apparently, some of the ants got out and then began to breed massively. Before too long, these fire ants were major players as insects across the world. However, this South American ant species was not able to do this by accident everywhere it is today.
You can find them in North America, Australia, New Zealand, as well as many Asian & Caribbean countries. The species could never swim well enough to make it to all of these places alone. Therefore, we know humans had to have introduced them on purpose at least for some of them. While an ant species might not be considered a huge problem to some, large amounts of one can be a huge problem for an ecosystem. If nothing else, it will be in direct competition with native ant species.
The Asian Tiger Mosquito is pretty impressive. It has managed to, in spite of all odds, make itself a major player on every continent on the planet outside of Antarctica. They are native to Southeast Asia, but a lot of things are imported from countries in this region. The tiger mosquito managed to make it to other countries due to these shipments. They came to the United States in a shipment of used tires back in the mid-1980s, spreading from California into other areas of the country. In 1979, they popped up in Albania (the first European country to see them).
By the 1990s, the species entered Italy & France and by the 2000s, they were spotted in Belgium, Greece, Switzerland, Spain, Croatia, and the Netherlands. Around these same periods, it popped up in Paraguay, Brazil, Bolivia, Cuba, Argentina, Panama, and many more. For some reason, several attempts were made to get them in Australia & New Zealand, which took forever to happen. Yet by 2006, they became commonplace in the Torres Strait. This mosquito is a horrible pest, notable invasive species, and should be ended at all costs. It carries viruses like Zika, Yellow Fever, Dengue Fever, and much more.
There is a lot that people can assume by “Feral Swine.” To be specific, we’re referring to wild pigs, boars, razorbacks, etc. The term “swine” is heavily inclusive here. Feral pigs happen to be because they were previously domesticated and either escaped or were released into the wild. They were actually first introduced to the American region by Christopher Columbus, who released them on the island chain he came across. They’d eventually be introduced to mainland North America too.
While the original introduction of the species was fine, things became problematic over time. Feral pigs seem to breed pretty well, and that can result in more pigs than can be hunted down. As a result, food slightly increased in Indigenous regions, but they eventually became a problem overall. Feral pigs are a notable invasive species due to repeatedly getting into agriculture, and even feeding on other animals that previously were the prey of native creatures. Not to mention the harm they have done to humans.
Lionfish are quite beautiful and are likely a popular fish at your local aquarium. They are now becoming a notable invasive species to other regions, in particular, the coastal United States of America. They had been thriving around the coral reefs in the Pacific & Indian Oceans for hundreds of years, without any problems. However, their decision to move away from this region is a massive problem. This marine ecosystem needs them tremendously.
Lionfish are key assets to both commercial and recreationally imported fish to the coral reefs. Lionfish hunt down pests that could harm these reefs. Those pests might also take down creatures that aid the reefs. NOAA and its partners are trying to fix things as best they can by bringing lionfish back to its home. However, climate change has led to many fish leaving their normal homes, including those native to the world’s coral reef territories.
Native To:Near East Region (Around 7,500 Years Ago)
Like the feral creatures on this list, Domestic Cats are a problem 100% due to human introduction. While you’ll see cat species literally all over the planet, the “domestic cat” is the furball you see around your home. You know what we’re talking about, that animal that ignores you and likely hates you in spite of the love you give them. While cats are not always a major issue, they are certainly a notable invasive species all around the world.
Even if they are in a loving home, many cats will hunt just to hunt. There is often no reason for them to do it, as they might not eat the animal they kill. Usually, this tends to be birds. They prey on many kinds and have the athletic ability to grab them right out of the air. They can be very helpful in reducing mouse or rat populations in and around homes. However, they might also hunt squirrels, chipmunks, and other small creatures that are important to local ecosystems too.
The Burmese Python is native to Southeast Asia, but for some reason that we’ll never understand, many people like keeping these snakes as pets. Pythons have become the most common snake pet worldwide. Yet in the United States, in spite of how large they can get, the Burmese Python is among the most popular pet snakes. There are many problems with this. While they can be good around humans, they are very strong snakes that can get kind of large.
Due to this, they often get out of wherever they are being contained inside a home. They can then hide and slither out of the house and into the wild. This has been happening a lot in the United States, especially in Florida. That has impacted the ecosystem heavily as these snakes will hunt for pretty much any prey it feels like. Barring humans, there is really very little off the menu for them. They are now a notable invasive species in the country and are illegal to have without proper permits.
When we refer to the “field mouse,” it’s pretty much including every common mouse around the world. As we know, mice are common all over the world, regardless of the country you happen to be in. There might be a different look for some compared to others. Some might be black while others are brown or gray, you’ll even see some white types too. In other parts of the world, there could be a variety.
They are among the most notable invasive species mostly due to our issue with them as humans. They often invade our homes, eat parts of our food, and leave nice dark presents for us. The species is a menace to society and we’ll do anything to get rid of them. So much so, we’ll introduce creatures to regions to help limit the field mouse species in our area. Proving, we’d rather deal with another invasive species than mice most of the time.
The Malaria Mosquito obviously gets its name from what it tends to spread, the Malaria virus. While mosquitos are now common to see all over the world, this specific species of mosquito mostly can be found in Sub-Saharan Africa. Naturally, it became a notable invasive species simply due to what it carries. Mosquitos naturally bite into the skin of animals and humans alike, and that is something you’re going to see with them all.
The difference here is that the species has the Malaria pathogen. The moment it bites into a human or animal, it then transfers that very pathogen. Of course, some people do not get sick from this. This is especially true for those who spot the mosquito before it has time to really do anything. However, the rest may contract the virus and get very sick. There are vaccines to cut the symptoms down and nets to keep them away as much as possible. However, it is still not enough.
To be fair, deer are found worldwide. There are some in the species that have been introduced elsewhere, however. This includes the Red Deer, which was introduced to Argentina, Australia, and New Zealand. Yet the most interesting thing about deer is that they are actually invasive to the place they are native. While it is true that some have been introduced, a place like the United States of America has been seeing deer for several centuries. It’s native to this land. The Whitetail Deer, for example, is widespread.
Yet the population has gotten out of control, especially during the time of year when hunting deer is not allowed outside private land. In fact, hunters are only allowed a specific amount per hunting season too. This is to help keep the population from being reduced too heavily obviously. Yet deer reproduce heavily, causing millions to pop up every year. They have interrupted agricultural territories, and they are even known for causing more car accidents than any other species in America COMBINED. This makes them responsible for over 200 human deaths per year.
This is actually the only animal on the list that is not actually native to any region. Known as the Africanized Honeybee, they have been referred to as “Killer Bees” by most people for a long time. This is primarily due to the fact that they have actually been responsible for many human deaths. How is it that this species is not native to any area? Killer bees are actually a hybrid bee species. They are a cross between a Western Honey Bee and East African Lowland Honey Bee.
The species was bred to see if there might be an increase in honey production with two species that do this well…just in different ways. The species was introduced to Brazil in 1956, confined in a quarantined area. This changed when in 1957, 26 swarms of the bee managed to escape. They began to breed heavily, making their way through South & Central America. By the 1990s, they managed to make it into North America. Killer bees have been a notable invasive species there ever since.
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