Cats among top 5 invasive pests in America’s national parks

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The National Park Service says invasive species are posing challenges to natural ecosystems, leading to threats to native wildlife and even humans.

Rangers say some of the invasive pests have been introduced accidentally, while others have been intentionally released into the wild.

Regardless of how they arrived, wildlife experts say their spread costs billions of dollars annually and leads to ecological harm.

Some of the most problematic species include stray and feral cats, beetles and even ants.

A cat stand atop a wall near a Lowe's parking lot on May 19, 2025, in Kendall in Miami-Dade, County, Florida.

(D.A. Varela/Miami Herald/Tribune News Service via Getty Images / Getty Images)

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The NPS considers free-ranging cats to be among the widespread invasive problems throughout more than 400 sites.

While cats that are kept indoors do not pose any risks, abandoned cats have been linked to declines in bird, reptile and small mammal populations.

Additionally, they can transmit diseases such as rabies and toxoplasmosis, which can even be harmful to humans.

NPS staff say they are better hiders than feral swine, or what are commonly known as wild hogs.

Pigs are thought to have been first introduced by European settlers but are responsible for destroying crops, native vegetation, and transmitting a host of dangerous diseases.

Three other types of invasive pests that park staff identified are rather small and sometimes require a magnifying glass to properly see.

One of the smaller types of vermin are red ants, or what are known as Solenopsis invicta.

Biologists believe they arrived in America during the 1900s from cargo that came from South America.

Since their arrival, these stinging insects have been reported in more than a dozen states and have led to damaged vegetation and injuries to humans and pets.

Two smaller types of invasive species include the emerald ash borer and the hemlock woolly adelgid, which are tiny insects that consume trees.

The Wisconsin Department of Natural Resources recently warned about the spread of the emerald ash borer through the movement of firewood.

The problem with the Asian beetle is said to be significant enough that the entire month of October is devoted to its awareness, which is known as National Firewood Month.

LIBERTY, ME - MAY 31: Colleen Teerling, Entomologist, Maine Forest Service Insect and Disease Lab, shows evil emerald ash borer specimens and the damage hey can cause on trees. She is researching if they have reached Maine yet.

(Photo by Carl D. Walsh/Portland Portland Press Herald via Getty Images / Getty Images)

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Rangers say that the five pests are only a fraction of a much larger invasive species problem that impacts every section of the country.

Dozens of other plants, animals and insects - from Burmese pythons in the Florida Everglades to kudzu, a fast-growing Asian vine that chokes out native vegetation – also threaten ecosystems.

To help cut down on the spread, the NPS recommends cleaning hiking and camping gear, not releasing insects or animals into the wild and only buying local, certified firewood.