Terrestrial Invasive Species

There are many terrestrial invasive animals that disrupt ecosystems in the Pacific Northwest. However, one species that most people don't realize is an invasive species is the domesticated cat, Felis catus. Those cute and cuddly companions are actually an exotic species in the United States and are responsible for the extinctions of many other species as well as the degradation of ecosystem health. Along with the extinctions of many bird, mammal, and reptile species, they are capable of outcompeting native predators (Duffy, 2012), can be vectors for diseases, and disrupt certain ecosystem processes, such as bird migrations and seed dispersal systems (Medina, 2014).

http://www.sfgate.com/blogs/images/sfgate/pets/2009/09/
30/3199138061_116b9c9964400x265.jpg

The main negative consequence of invasive cats is their predatory habits. Cats are excellent predators that can replace native apex predators and disrupt certain ecological processes because of that. Although feral cats seem to be the bulk of the issue, even well-fed cats will still continue to hunt birds, mammals, and reptiles, leading to the extinction of many species. Cats have contributed to "at least 14% of all modern bird, mammal, and reptile extinctions (Medina, 2014)" and are responsible for the endemism of many species as well.

Original Figure: The number of animals that are killed each year by cats in the U.S.
http://www.smithsonianmag.com/science-nature/
feral-cats-kill-billions-of-small-critters-each-year-7814590/?no-ist

Cats are also responsible for the transmission of many diseases to humans and other organisms, with their feces being the main vector for disease transmission. Toxoplasmosis is one of the many diseases that cats are responsible for transmitting. Toxoplasmosis can be transmitted to humans through ingestion of uncooked meat or soil, inhalation of dust, soil, or cat litter, or ingestion of water contaminated by cat feces. Pregnant women that are infected have a higher incidence of miscarriage or stillbirth and children who are exposed to the virus in the womb are susceptible to blindness, encephalitis, and developmental retardation. Cats can also be responsible for cat-scratch diseases, human gastric diseases, rabies, and many other diseases, as well as diseases that can be transmitted to other organisms (Medina, 2014).

Medina, 2014
Effects and consequences of invasion and establishment of cats. 

Just like most other invasive species, cats are also responsible for the decrease in native population sizes and the disruption of ecological interactions through competition (Medina, 2014). They tend to challenge native species very competitively for resources such as food and habitat, resulting in the suffering of species that are out competed by cats. This invasive species has also been found to alter other ecological processes, such as bird migrations and seed dispersal systems. During bird migrations, birds must make stopovers so they can refuel and rest. Birds consider fuel load when they are picking a site to stopover at, but predation risk can trump fuel load at times, thus leaving the birds more vulnerable and with less fuel. Cats can also disrupt the seed dispersal systems that rely on frugivorous animals. Cats often kill these frugivorous animals, thus halting the seed dispersal of many native plants. Cats cause a lot of problems in several areas and are an issue that needs to be controlled and regulated immediately.