This week, the Minneapolis City Council is likely to adopt a policy permitting caretaking of feral cat colonies in an effort to address what has become a national debate: Should we care for feral cats or curb their populations?

Those concerned with feral cats’ rights prefer control programs that minimally impact the cats’ quality of life, such as “trap, neuter and release” (TNR) programs. Those concerned with the ecological impacts of feral cats favor reducing populations through euthanasia programs.

The national debate over feral cat policy intensified in January when an article in the journal Nature Communications estimated that the impact of unattended cats on wildlife was higher than previously thought. The validity of these estimates since has been scrutinized, distracting us from the question that underpins the disagreement: Do we value the rights of feral cats over those of the species on which they prey?

I seek to clarify misconceptions about the science cited in arguments against TNR programs. While such research is used by folks concerned with the ecological impacts of feral cats, the research is not driven by the debate. Science does not have it out for feral cats. Rather, scientists strive to provide data-centered information to clarify the ecological relationships in question.

Do cats really kill birds?

The January 2013 study estimates that each year free-ranging cats kill between 1.4 billion and 3.7 billion birds and between 6.9 billion and 20.7 billion mammals. The authors have been criticized for not having collected their own data to derive their estimates. However, analyzing the results of the pool of published scientific studies on cat predation is a powerful way to address the question at the national scale.

By developing models based on estimates from other peer-reviewed studies, the authors were able to account for variation in cat kill rates across the country. Because of this, their estimate is more representative than a local study of the predation rate on a national scale.

Their conclusions were reinforced by a camera study published this year by researchers at the University of Georgia. That work tracked the predation rates of individual cats.

Those favoring caretaking of feral cat colonies tout TNR programs as being more effective than euthanasia in controlling colony size. Neither program is effective at reducing feral cat populations unless they are used much more aggressively than they currently are in Minneapolis.

TNR programs attempt to restrict the growth of feral cat colonies, while euthanasia programs seek to directly reduce the population. Models published in the Journal of the American Veterinary Medical Association suggest that in order to reduce the size of feral cat colonies, more than 75 percent of free-roaming cats in a population would have to be neutered annually, while 50 percent euthanasia would achieve the same outcome.

Furthermore, TNR programs haven’t been effective in limiting population growth unless used in combination with adoption and euthanasia. Euthanasia is a more effective way to directly reduce colony size.

Let’s refrain from questioning the science and discuss what lies at the heart of this debate: whether to prioritize the rights of individuals within a free-roaming, nonnative pet species over the persistence of our native biodiversity.

If part of our responsibility is to preserve Minnesota’s natural heritage, we are obligated to manage nonnative species we’ve introduced to minimize their impact on our native wildlife.

While we look at cat as pets, feral cats are no exception to this obligation. Our native birds continue to decline due to habitat loss and nest predation.

Science can help inform our values, but the ultimate decision reflects our priorities.


Hannah Specht, of Minneapolis, is a graduate student fellow in conservation biology at the University of Minnesota.