Pollution And Wildlife Problems

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    In the past 40 years, the number of domestic cats in the United States has tripled. Regardless of how cats are classified (inside/outside house cats, free-ranging, feral or semi-feral), it is possible for them to have adverse effects on native wildlife populations due to their predatory nature. Feral and free-ranging cats can potentially lead to devastating impacts on native animals.

    Research in Hawaii has shown feral cats to be frequent predators of endangered Hawaiian birds. Annual mammal mortality due to cats in the United States has been estimated to be between 6.9 and 20.7 billion, with 89% of the mortality caused by un-owned cats, including farm/barn cats.

    Research has also suggested that farm/barn cats living at higher densities and receiving some food from humans and can have substantial effects on local native animal populations. Cats affect not only native prey but possibly out-competing native predators. Regular access to food provided by humans does not suppress hunting behavior in cats, and they may continue to kill even when prey populations are low.

    While free-ranging cats may have a beneficial role in controlling the non-native rodents on a farm, they put extreme pressure on native wildlife as well. Cats are also known to prey on other animals such as invertebrates, reptiles, amphibians and birds. On islands have been implicated in local extinction of birds and reptiles.

    Interesting Facts:

    1. In a small community of about 300 adult residents, a population of 7,284 owned and 2,046 feral cats contribute to over 100 tonnes of feces to the environment per year. Unlike noncat owners, cat owners are notorious for opposing cat licensing or being concerned about water pollution.
    2. Despite the short duration of Toxoplasma gondii oocysts shedding by cats, the sheer numbers of oocysts shed by cats during initial infection can lead to substantial environmental contamination. The annual burden in the environment by cats shedding Toxoplasma gondii oocysts is 434 oocysts per square foot which poses the potential threats by cats to human and wildlife health.
    3. Household and stray cats incessantly contaminate the environment with the eggs of Toxocara and other helminths.


    1. Dabritz et al. – Outdoor Fecal Deposition By Free-roaming Cats And Attitudes Of Cat Owners And Nonowners Toward Stray Pets, Wildlife, And Water Pollution
    2. Dabritz et al. – Detection Of Toxoplasma Gondii-like Oocysts In Cat Feces And Estimates Of The Environmental Oocyst Burden
    3. Kitts-Morgan et al. – Free-Ranging Farm Cats: Home Range Size And Predation On A Livestock Unit In Northwest Georgia


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