Five Animals and Insects You Didn't Know Were Invasive (and Their Native Counterparts!)

By Clara Wodny on February 21, 2025 in Blog

When it comes to Iowa’s invasive species, most available information focuses on plants that spread quickly, cause harm to beneficial or rare species, and have a negative impact on an area’s biodiversity or otherwise harm the landscape. But, did you know that animals and insects can be invasive as well? An invasive species is any kind of living organism that causes harm to an ecosystem and is often (though not always!) non-native.

Among animals and insects, invasive species typically spread and reproduce quickly, competing with more beneficial native species for food and habitat. That being said, it is important to note the difference between non-native and invasive species. Just because a species is not native to a certain area does not necessarily make it invasive, and some native species are still considered invasive. For more information on the differences between native, non-native, invasive, and non-invasive species, check out this blog post.

In many cases, invasive animals and insects can be hard to identify because they are so common, or they are easily confused with their native, beneficial counterparts. Here are five common Iowa species that you might not realize are invasive, and how to identify them:

1. House Sparrows

House sparrows (Passer domesticuscan) now be found in most parts of the world, but they originated in Europe. They were first introduced to the U.S. in 1852 in hopes they would be able to control the populations of common pests. They are tough, adaptable and aggressive, and have become one of the most widespread and abundant songbirds in the U.S., despite their negative impacts on native species.

House Sparrows are known to be harmful to other birds, including native species like Eastern Bluebirds and Purple Martins. They reproduce rapidly and will outcompete other birds for food and habitat. House Sparrows are known to forcefully take over already-established nesting sites, sometimes killing native birds in the process. Because they are legally recognized as an invasive species, it is perfectly legal to take down their nests and discourage them from repopulating.

There are many types of sparrows in Iowa, some of which are native, and it can be difficult to tell the difference between species. Compared to most native sparrows, House Sparrows have fuller chests, rounder heads, shorter tails and stouter bills. Males are brightly colored with gray heads, white cheeks, and a black bib, while females area duller brown with gray bellies. House sparrows can also be identified by their behavior — they tend to be much more active and aggressive than their native counterparts.

2. Carp

There are many species of carp in Iowa, but several — including Bighead Carp (Hypophthalmichthys nobilis), Silver Carp (Hypophthalmichthys molitrix), and Black Carp (Mylopharyngodon piceus) — are now considered invasive. Originating in Europe and Asia, various species were introduced in Iowa throughout the 1900s, often by fish farmers.

Carp grow, reproduce and spread quite quickly, often competing with native fish for food and space. The Bighead Carp is the largest carp species in Iowa, growing up to 60 inches and weighing over 100 pounds! Because they are so large and densely populated, they have the potential to deplete plankton populations, in turn harming the native species that also rely on plankton for food.

3. Chinese Mantis

The Chinese Mantis (Tenodera sinesis) is one of two mantid species regularly found in Iowa. They tend to be mostly brown with a green stripe along the outside of their wings, and can grow up to 4.25 inches.

Chinese Mantises pose a great threat to native species, including the native Carolina Mantis (Stagmomantis carolina). Their larger size and aggressive nature mean they often outcompete Carolina mantises for food and habitat. They have also been known to consume other mantids, various pollinators and even hummingbirds.

4. Multi-colored Asian Lady Beetles

Asian lady beetles (Harmonia axyridis), originally from Asia, were first released in California in 1916. Introduced with the hope they would control and reduce other pest populations, they began to spread across the U.S. in the 1970’s and 80’s. While they were never released in Iowa, they are now a permanent resident of the state, having likely flown from Louisiana or hitchhiked on vehicles.

Asian lady beetles are commonly confused with native ladybugs. Compared to ladybugs, Asian lady beetles tend to be slightly larger and have more color variation. Their forewings can vary widely from tan to orange to red. Many have black spots on their wings, but some don’t — beetles with more spots tend to be female, while unspotted ones tend to be male. One easy way to check if you’re dealing with an Asian lady beetle or a ladybug is by examining their head- —most Asian lady beetles will have a small  black mark that looks like an “M”.

Like many invasive species, Asian lady beetles pose a threat to our native ladybug species by competing for food, habitat and other resources. Asian lady beetles are also hardier and stronger than native ladybugs, and will often introduce diseases that negatively impact native species.

5. American Bullfrogs

Considered an invasive species in Iowa, American bullfrogs (Lithobates catesbeianus) are native to the eastern United States. They have spread all over the world to other parts of America, Europe, Asia and South America, causing substantial ecological disruptions. Introduction to Iowa most likely occurred because of fish stocking, where they escaped aquaculture enclosures.

American bullfrogs will occupy any type of habitat that is near to slowly moving water, especially if there is an abundance of aquatic and/or bank vegetation. Bullfrogs are voracious eaters and will consume pretty much anything they can fit in their mouths. This includes other amphibians, snakes, turtles and even small birds and rodents. They are detrimental to other frog populations, especially in places that didn’t previously have a population of American bullfrogs.

In some cases, invasive species have become so common that most people forget or never realize that they are not a native species. For example, American bullfrogs are now Iowa’s most common frog species. Recognizing these threats and understanding the impact they have on our native wildlife is crucial for preserving biodiversity. By raising awareness about these invaders, we can take steps to manage and protect our ecosystems, ensuring a healthier, more balanced environment for future generations.