A Little Bit More
I happen to be a cat-lover so be assured that writing this unit is not designed to turn off people to cats but simply to help everyone understand the issue. And, it’s a big issue if you realize that about 7.8 million birds are killed by cats in Wisconsin each year! If you feel those numbers are not reasonable, halve them and you’re still dealing with millions of unnecessary deaths. No one is saying people shouldn’t have cats but just as human population pressures are making it more and more difficult for people to have free-roaming dogs, cat-lovers need to recognize their own responsibility to society and the natural world.
In a natural setting, predators are very much a part of a normal, healthy environment. But, when cats are introduced artificially into the system, they put additional pressures on the animals that live there - both predator and prey alike. Cats don’t rely on the food they catch to survive so their owners make it possible for them to roam the countryside hunting for “food” in artificially-high predator populations.
Not everyone agrees that cats have a negative impact on wildlife, correctly pointing out that many human activities account for most problems for our wildlife. But no matter to what degree cats have an impact on wildlife, it doesn’t take a rocket scientist to realize that free-roaming cats do add to the pressures exerted on wildlife right along with all of the other human-caused negative effects. Although there may not be agreement on the actual numbers that are affected, keeping cats indoors seems like a simple enough solution on this particular issue – pet owners can still enjoy their cats without putting unnecessary stresses on wildlife populations.
Activities
Math – U.S. and Canadian Bird Kills
Objectives: Use a mathematical approach to answer a valid environmental question
Materials: Internet access
We’ve pointed out that studies showed that about 7.8 million animals were killed by Wisconsin cats in one year. This is a staggering number of animals! By using the Wisconsin figures, we should be able to get a VERY rough estimate of how many small animals are killed in the U.S. and Canada each year. This is going to require some basic assumptions on our part but it should give us an idea of what kind of overall numbers we’re talking about – a ballpark estimate, if you will.
- Since some people are unhappy with the 7.8 million animals killed in Wisconsin, let’s be conservative and drop that a bit for this exercise. So, let’s use the number 5 million as our number of animals killed by cats in Wisconsin in a single year.
- If we compare this number with the number of residents in the state, we can obtain a ratio of animals killed per resident. (you should be able to get the latest population figures on the internet for Wisconsin)
- We now need to determine how many residents live in the U.S. and how many live in Canada. (you should be able to get the population figures on the internet for both countries)
- If we assume that the ratio of animals killed by cats in Wisconsin is similar to those of the other 49 states and 13 provinces, we can use this ratio with Canadian and U.S. population figures and roughly determine how many animals are killed in these two countries.
Granted, this is not a very scientific way to achieve this information but it does give us an estimate that is probably in the right “ballpark”.
An easy example that you might want to share with students could look something like:
5 million animals killed in Wisconsin/ 10 million Wisconsin residents = a 1:2 ratio
so we can use X for animals killed in Canada and U.S. / the population of Canada and U.S. Based on the Wisconsin ratio then, we should find that our unknown (X) is 1/2 that of the population of Canada and U.S. combined. Voila!
Key Concepts
Environmental Issues, Predator/Prey Relationships
Questions
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