Green Anoles, Anolis carolinensis, is a native to the south that is being displaced by Cuban Brown Anoles, Anolis sagrei.

A Look At Invasive Species

As much as many would like to deny it, the fact that invasive species are one of the greatest threats to native ecosystems is no big secret. As one of the hotbeds for invasive species, here in Florida we have invasions ranging from the highly publicized reports (often bordering on fear-mongering) of invasive giant pythons (primarily the Burmese Python, Python bivittatus) in the everglades to the ubiquitous and often overlooked Cuban Brown Anoles that live in virtually every yard across the state. Across the country, there are invasive populations of many species of animals and plants that receive various levels of attention. With the seemingly never ending list of non-native species that have been able to gain footholds in new areas, we have to ask how this happens, how do we stop it from continuing, and what role have we as pet hobbyists played?

Introduced vs Invasive

Currently, nobody knows exactly how many non-native species can be found living in the United States, and it is likely that nobody will ever know this number. One report from Cornell University claimed that there were 50,000 non-native species in the United States, and some argue there are even more than that. However, one thing that must be remembered is that not every non-native species that may be present is going to be invasive.

Some species are in some way introduced but never gain any foothold to establish long term population. Sticking to examples here in Florida (because there are so many), there are Parrot species that have managed to escape from facilities but simply are not reproductively successful and will not continue past the current generation. These species also do not create any significant pressure on native species in terms of competition for food or living space so there overall impact is negligible.

Similarly, even some species that can establish viable reproductive populations may never expand beyond a small area. For almost twenty years, there has been a population of Mexican Red Rump Tarantula (Brachypelma vagans) living in a citrus orchard that has successfully been reproducing but has not expanded beyond one small area or demonstrated any adverse effect on any local native species.

In order for an organism to be considered invasive, it must not only be non-native but also be capable of causing environmental, economic, or human harm. Many times, the environmental harm is what first comes to mind and includes the ability for a species to reproduce rapidly, have few enemies, and out-compete native animals for living space or food (and thus causing a decline in natural populations). Certain species can cause a large amount of economic harm by destroying agricultural crops or damaging man-made structures which must then be repaired or replaced. Finally, there are several ways in which invasive species can cause human harm such as through actual physical conflict or by being vectors for introducing diseases.

A Historical Change of Attitude

In all of the discussions surrounding invasive animals, one fact that is often overlooked and rarely mentioned is how startlingly quickly and recently the general attitude regarding human impact on the environment has been. For most of history, relatively little concern has been given to how we affect the world around us. While there have long been small pockets of people that have brought up these topics, they were always the vast minority. Even as I was growing up in the south during the 1980's, people who made strong objections from an environmental mindset were ridiculed and belittled. Not that long ago, "tree hugger" was an insult and the opinions of those who were perceived as such were typically discounted.

Over the past couple of decades, the pendulum has begun to strongly move in the other direction. More and more people, at least in developed nations, are becoming aware of the impacts of their decisions. Where fifty or one hundred years ago most people were primarily concerned with their day to day routines, increasing attention is being paid to the long term ramifications of our actions. Where once exotic animals may have been released to allow them to freely colonize an area as a tourist attraction (a practice that was fairly common here in Florida), this is now being frowned upon as we realize the potential harm that this can create. However, the transition to this mindset is not complete, and we are now facing a period of conflict between those who want to prevent any long-term consequences and those who still do not believe that those consequences are all that serious.

Intentionally Introduced Invasives

Some of the most problematic invasive species are those that were purposefully introduced. For almost as long as European settlers have been arriving in what is now the US, there have been plants and animals released for the convenience of those who live here. Wild pigs were released as far back as the 1500's for free-range farming as well as for stock to hunt. Unfortunately, these feral pigs are now an extremely destructive invasive species that have been reported in at least 45 states.

One of the most well-known invasive plants, kudzu, was originally imported into the United States in the late 19th century as a form of ground cover to prevent erosion. Due to its ability to climb virtually any structure, it gained popularity as an ornamental plant for providing shade on patios and was found to be a useful food source for various forms of farm livestock. Unfortunately the climate of the southeastern United States has proven ideal for kudzu and it has been able to spread virtually unchecked without any natural forms of control.

Similarly, water hyacinth, first introduced as an ornamental plant in the late 19th century, has been utilized in attempts to absorb nutrients and reduce the presence of algae but quickly spreads out of control. Thick mats of it block water flow, prevent boats from using waterways, block sunlight from reaching native underwater plants, and hinder oxygen exchange, resulting in lower levels of dissolved oxygen in water making respiration more difficult for native fish.

While many of these and other species were released from an attempt to solve problems or improve quality of life, there was little if any consideration given to the long-term impacts they could have. At the time many of these were released, there simply didn't exist the foundation of knowledge to make the educated decisions that we can now make.

Ballast Water – One of Today's Biggest Threats

One of the most prominent sources for invasive aquatic organisms that exists in today's world is the use of ballast water in shipping. Put simply, most large ships utilize a certain amount of water in ballast holds to add extra weight and increase stability when sailing. However, this extra water is removed before docking to allow it to float higher and fit into shallower water. As the boat is leaving where it is docked, it will pump in a large amount of water which often contains a number of different organisms. These organism are then carried in the belly of the ship until they reach their destination port where they are then pumped out with the water, giving them access to an entirely new habitat.

There are estimates that 7,000 or more species are carried in ballast tanks around the world. Even if the vast majority of these species die during transit, there are hundreds of potentially invasive species being released constantly. With the right individuals of the right species arriving in the right place, it is inevitable that some of these species will thrive. While there have recently been increasing measures taken to reduce this risk (such as exchanging ballast water in the middle of the ocean where few if any species can survive), it is still not a perfect system.

One such example of invasive species being introduced via ballast water is the invasion of Zebra Mussels (Dreissena polymorpha) and Quagga Mussels (Dreissena rostriformis bugensis) to the Great Lakes. After being transported via ballast water, they have become so successful that they are causing immense environmental and economic damage.

Environmentally, these mussels not only encrust over top of native mussels (thereby smothering them), they also filter out significant amounts of phytoplankton and other suspended particulates from the water. This phytoplankton is the base of local food chains which substantially affects the survivability of all other organisms that directly or indirectly rely on it. In addition, although they are edible for larger animals such as birds, their filtering ability frequently causes high levels of toxins to build up in their bodies which can poison birds that might eat them.

Economically, Zebra and Quagga Mussels have caused problems by rapidly and thoroughly encrusting most surfaces they can find. They commonly encrust so heavily that they can clog pipes and intakes at such places as hydroelectric and water treatment plants. They can also damage boats, docks, buoys and other structures and their sharp shells discourage recreational activities.

Accidental Introductions

Certain species are introduced to new areas when they arrive as accidental hitchhikers on other products. Individual may find their way into packing crates or other shipping materials and eventually make their way into new habitats. One major example of this is the Cuban/Bahaman Anoles that have displaced many of the native Green Anoles in Florida. Once they made their way from the seaports to the mainland of Florida they rapidly spread. They have since made their way unobserved to other parts of the United States through such methods as hiding in ornamental plants farmed in Florida and shipped to other states.

One of the most famous accidental introductions is the Brown Tree Snake (Boiga irregularis) that was introduced from the northeast of Australia to Guam most likely by stowing away in cargo crates. Since its introduction in the late 1940's, it has abundantly reproduced to the point of leading to the extinction of a number of species on Guam. Additionally, it has been responsible for a number of other problems, particularly by causing power outages from climbing on electrical wires.

The Volitans Lionfish (Pterois volitans) is perhaps one of the most widely publicized recent invasive species, spreading throughout the Caribbean and up the Atlantic coast.

What affect have we had?

While most of the invasive species are introduced to new areas through the above methods, exotic animal owners still get a heavy burden of blame, and this is the area that we as pet owners and lovers need to be concerned with. How many of these are actually the result of our actions, though? Unfortunately, there is not and will not be a reliable answer to this as there is no reliable way to know where an animal came from. There are also unfortunately few if any resources giving concrete evidence on how and why captive animals may make it into the wild.

I think it is naïve and unrealistic to claim that animals are never released or escape from captivity. However, I wholeheartedly believe that the number of instances of this happening is significantly lower now than in years past. Thirty, fifty, seventy five years ago, many people wouldn't think twice about releasing animals that were no longer wanted or that they could no longer care for. As we have progressed in the way we view animals and the environment, more and more people are starting to realize the potential problems that can arise from dumping unwanted pets. Additionally, with the proliferation of (mostly) free and accessible information on the internet, keepers can be better informed and better prepared to take care of animals for their entire lives.

There are bound to be those unscrupulous people who acquire a pet not knowing or caring how to keep the animal for its entire life and who eventually dump the animal when it becomes inconvenient to keep it anymore. However, the majority of captive releases likely come from a much more innocent source, those who think they are doing what is best for the animal by releasing it and allowing it to live a "natural" life.

One significant change over the past several decades has been the rise and increasingly vocal group of individuals calling themselves "animal rights" activists (not to be confused with those who advocate for animal welfare, which is an entirely different set of beliefs). One of the primary messages that animal rights groups spread is that every animal should be living "free" in the wild. Unfortunately, once an animal has been transported outside of its native range and kept as a pet, releasing it into the wild can be cruel towards the animal and potentially devastating to native species.

Hobbyists' Role and Preventing Release

There is a seemingly never ending stream of questions regarding how to handle the problem of invasive species, particularly in regards to those animals that may be introduced from the pet trade. The quick and popular answer is simply to ban the animals in the first place so that there will (theoretically) not be a chance of them becoming introduced. In reality, this is not an effective answer as bans rarely if ever truly work. You merely have to look at any of the many bans that have been implemented and failed over the years, such as bans on alcohol, drugs, guns, driving with cell phones, or travel bans designed to prevent the introduction of diseases.

There is no easy, one step solution, but progress must begin with education, and it is up to the keepers to take the time to educate themselves on the needs of the animals before they acquire them. Fortunately, we are living in a world with unprecedented access to an enormous collection of knowledge and experiences. Forums, hobbyist magazines, and websites such as Habitattitude can all guide owners as they look into buying a new pet. Whenever you want to bring home a new type of animal, do research and ask questions to ensure that you are prepared and that the animal is the right fit for you. It is up to us to utilize these resources and make responsible decisions.

The reason that we as hobbyists begin keeping animals in the first place is because we have a deep love and fascination for animals and nature. We owe it to these animals to best possible care for the entirety of their lives. We are fortunate to have the access and communal knowledge to keep a wide range of pets. However, if we do not act responsibly, we risk losing the ability to keep them at all.