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Jon Cox

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Cats pose a serious threat to biodiversity: Why do we accept it? What should be done?

According to the ASPCA, there are around 90 million owned domestic cats (Felis catus) in the U.S., and taking into account strays and feral cats, the total number is estimated to be as high as 160 million (1). Loss et al. (2013) estimates that cats roaming outdoors kill 1.4-­3.7 BILLION birds and 6.9­-20.7 BILLION mammals in the U.S. annually (2). Reptiles and amphibians such as snakes, lizards, frogs, etc., are also frequently killed by cats.

Cats are even more popular New Zealand, where they are contributing to declines of endemic birds such as the critically endangered kakapo (3), which have evolved in the absence of predators. Businessman/philanthropist Gareth Morgan is trying to gather support for legislation that would aggressively deal with stray and feral cats and potentially eliminate cats from New Zealand to take pressure off of threatened species (4 & 5). With Morgan’s plan, in addition to regulation that would reduce cat populations and increase owner accountability, residents would be encouraged to not replace their cats. As of now the majority of New Zealanders surveyed are in opposition to Morgan’s initiative.

Would a proposition like Morgan’s meet similar resistance in the U.S.? Probably, but is he on the right track? Would you personally support something like it for your state or country? Why or why not is it a good idea? Is this type of legislation necessary to curb the problem and protect wildlife? If you disagree, what are some alternatives? Will the aesthetics and familiarity of cats keep them off limits to such ideas in the opinions of the general public?

1. http://www.aspca.org/about-us/faq/pet-statistics.aspx
2. http://www.abcbirds.org/abcprograms/policy/cats/pdf/Loss_et_al_2013.pdf
3. http://www.avianweb.com/kakapo.html
4. http://www.npr.org/blogs/thetwo-way/2013/01/24/170191917/new-zealand-environmentalist-wants-to-eliminate-cats-to-save-birds
5. http://www.livescience.com/26525-cat-eradication-new-zealand-save-birds.html


Closing Statement from Jon Cox

Thanks to everyone who contributed to a thought provoking discussion!

I think we can all agree that we need to be responsible with our pets! For the sake of ecological and human health. And pet owners must realize that their carelessness is costly. Plans to completely eliminate cats from areas where they are very popular are pretty far fetched, but stricter regulation is a must, and domestic cats do NOT belong in the wild, period. Feral cats need to be seen and dealt with just as any other invasive species. However, extreme caution is necessary in any attempt to remove them where they have become established as a keystone species.

Check out Australian cat laws for a look at the legislation adopted by a people who cherish their native wildlife and do not want to see it be destroyed by invasives.

And lastly, we must keep in mind that invasive species are just one way in which we threaten biodiversity. Overexploitation and especially habitat loss pose even greater threats to species survival.

Thanks again!


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    May 7 2013: Attempting to find scholarly articles on this topic proved a little difficult, so I’ll just discuss some of my thoughts and attach the best piece of research I found on the topic.

    In island nations such as New Zealand I can understand the need for more extreme measures to control cat population due to the characteristics of many New Zealand fauna that make them more susceptible to cat predation. Some of these characteristics include small size, terrestrial foraging or breeding habit, and isolation in native habitat fragments.

    However, in urban environments I see more problems resulting from the extermination of cats. It is mostly small mammals, birds, and reptiles that are subjected to predation by cats. As much as I can appreciate the conservation of many species, do you really think that people in urban environments are going to be happy if urban populations of rodents and birds significantly increase?

    From what I have read there are some legislative controls on cat activities in different areas across Australia that have been going on for a decade. I think the best plan of action is to use these areas as case studies to fully understand the effects of removing cats from the ecosystem. I also think it is important to take each environment (urban, suburban, etc.) and consider the impacts on an individual basis. For example I think cat populations in urban environments, where we know diversity of species is already reduced due to human impacts and urbanization, play an important role at this point and without them pest populations could become an issue.

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      May 7 2013: I agree with you Eleni. I'd like to add though that the usefulness of cats as pest regulators extends beyond urban environments. Many people living in the country, especially those with barns and sheds have cats to get rid of mice, and even birds that live in the rafters and the like. While yes, there also will likely be collateral damage with those species we are concerned about, there is also an undeniable benefit to a feline presence in both these areas and urban areas.
      As you said, people in these environments wouldn't be too happy to see rats running around, so the next alternative would likely be pesticides, which we know will have their own set of undesirable side-effects. While there are certainly downsides to having so many cats around, I believe it is a necessary evil. However, to help solve the problem, more animal control measures on feral cats could help reduce the unwanted deaths of native and threatened species.
      • May 7 2013: Hey Derek,
        where we live, in a woodsy, rural area, our cat has been undeniably handy in keeping the explosive rabbit population under control!
        And on a side note, our cat indirectly teaches my kids a valuable lesson of life and death. When they go outside to play, they are often confronted by half-eaten mouse/rabbit/bird carcasses. My initial instinct was to shield them from this 'horror', but that was impossible, and as it turns out, unnecessary. They accept that there are predators and prey, that animals have different needs than humans, and that where there is life, there is death. A cat symbolizes the raw aspects of nature that children need to be aware of.
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          May 8 2013: I agree, Lizanne. I grew up in the same sort of area. My parents still live there. No rabbits though. Mostly mice and voles. The moles and gophers I take care of myself when I'm around and have time for a stakeout.
          In addition to the lessons you mentioned, it also teaches people to watch where they step ;)
          Only had to make that mistake once...

          But anyway, back to you said, I totally agree and I think that that sort of realistic outlook is something kids are losing as more and more people live in cities. They never see what the real world is like outside of their sterile bubble.
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      Mario R

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      May 7 2013: While you bring up a good point Eleni, I think that rodents, and birds, both serve a purpose in urban environments. For example, squirrels, mice, and birds all aid in seed dispersal. By eliminating significant numbers in these populations, seed dispersal will be hindered.
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        May 7 2013: I agree with you Mario, I am sure they do play an important role in urban environments. Have you come across any news articles or scientific articles discussing a lack of these critters in urban areas? From personal experience I see lots of squirrels, mice, and birds around Eugene despite the large domestic cat population.
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          May 8 2013: i like the point you brought up eleni about how cats do keep certain populations down. Maybe the cat populations just need to be regulated for certain areas? That being said, is that even fair to do?

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