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Guest article by Ingrid R Niesman MS, PhD
For countless reasons, cats pose a dilemma for conservation biologists, rescue groups, and municipal politicians, as each of these groups views cats differently.
Conservationists consider cats to be apex predators. Animal welfare groups want to see more cats go to good homes or receive supportive care. Local authorities are accountable to voters, who are often at odds with public policy decisions. At the center of all discussions is the unexplored question of how many cats are there?
During the recent EveryCat Health Foundation Symposium, the second day was devoted to raising awareness of new aspects of cat life beyond medicine. Veterinary science covers shelter medicine and the health of pet cats. The left out group of cats are ownerless cats.
Explain animal population dynamics
Very little is known about these living, usually secretive felines that live without an owner. Above all, how many are there? Where do they live? Do they move between different populations?
In an extensive study based in Washington, D.C., an unusual collaboration of interest groups from all walks of life came together using the best sampling techniques in wildlife biology to critically assess populations of the three categories of cats: protected, owned and unowned. Their goal is not just to assign numbers, but to put populations in the context of locality and human influences.
Lead author of the DC Cat Count study (DC Cat Count, 2022) DT Tyler Flockhart states that the need for facts rather than unsubstantiated estimates is the overriding rationale for this study. “Difficult conversations are easier to have with accurate data. We can build trust and have productive discussions. The number of cats is at the center of everything.
The DC Cat Count is already providing important new insights into what Dr. Flockhart describes as the “rewilding” of cities. Cats exist as a functioning system, a fluid network. They are unique in that they exist in both a fully owned inner capacity and a fully wild existence. How the separate systems work together tells a more complete story of cat populations. Dr Flockhart shared that the main drivers of cat abundance appear to be housing density, land use and distance to shelters. The most surprising driver is the inverse relationship with income.
A global need for chat numbers, not just in the US and Canada
North America isn’t alone in trying to control cat populations. Two additional cat population assessment studies were published in 2021 and 2022 in the UK and Denmark (United Kingdom, 2021.) Like the DC Cat Count, these authors want to reset the baseline to their home country.
Peter Sandøe, from the Department of Veterinary and Animal Sciences, University of Copenhagen and author of the danish study, explains that for decades 500,000 cats was the accepted value of the total number of unowned Danish cats. Where that figure came from is unclear, but it still guided policy. Unfortunately, according to Danish environmental law, the domestic cat is classified as an invasive species. Therefore, there are severe restrictions on the establishment of TNR colonies, of which there are not many. Approximately 3,000 to 5,000 trapped cats per year are routinely euthanized.
Dr Sandøe argues that “cats have existed in Denmark since the Iron Age and have been numerous since Viking times”, suggesting that they are not invasive. As for the numbers, his group combined random sampling from all regions of Denmark using 120 veterinary students over a weekend to collect almost 2,000 questionnaire responses on local (socialized) or feral strays ( unsocialized) spotted in the neighborhoods. They added GPS-tracked cats to get important information about cat home ranges so they could calculate possible overlaps between spotted cats.
With a high degree of confidence they estimate the Danish population to be less than 100,000 unowned cats, or significantly less than half a million cats. A third of this population represents socialized cats who will usually go to shelters from where most of them find new homes. The remaining unsocialized cats will either need to be left on their own, neutered and released under the supervision of foster hosts, or will need to be euthanized. Dr. Sandøe clearly states: “The number of feral cats is not the problem in Denmark.”
Where do cats live?
“Cats live where humans live,” according to Dr. Sandøe. Dr Sandøe and his colleagues asked forest managers how many cats they encountered. Unsurprisingly, the answer was always zero. Data from all three studies support this hypothesis. In the UK, the highest population densities are concentrated around large urban areas. The graphic data presented during the symposium shows a high number of cats observed in more heavily urbanized areas. However, according to Dr. Sandøe’s study, the majority of unowned Danish cats lived in rural areas.
How to reasonably count cats?
The three studies varied in their research methods. The common thread is the involvement of citizens in their census. All studies used some variation of questionnaires. The DC study combined camera trapping and expert observers walking pre-planned routes.
Either way, the biggest hurdles are what you reasonably anticipate, identifying and categorizing individual chats. Many owner-owned cats have access to the outdoors. Feral cats are experts in isolation and easily go unnoticed. DC study observers walked their routes at dusk in hopes of seeing cats emerging from hiding.
Due to these constraints, all studies rely heavily on statistical modeling, techniques developed and widely used by wildlife biologists. Despite the disparity between the samplings, all three studies yielded actual cat numbers and densities for their respective regions with a high degree of confidence. Interestingly, censuses reflect that earlier estimates were clearly over exaggerations of populations. With a growing public sentiment in support of cats, demonstrating that they are not as big an issue as once thought in urban areas can drive a different conversation.
What about cats in your community?
An important offshoot of the DC Cat Count is the new toolkit for communities to replicate their methodology (hub.dccatcount.org). “We set up people to do their data collection,” says Dr. Flockhart.
Obtaining an accurate census of cats in the various ecosystems of the United States is extremely valuable data. As citizens, you can help launch this collection in your communities. The toolkit provides clear, written instructions for citizens, not scientists, to assess cats in their areas.
why it matters
An open and burning question for citizens, conservationists and wildlife managers is the role of domestic cats in ecosystems. They have been a neglected component of the complex interactions of species in urban and wild niches. We cannot assume that they are solely responsible for the decline of our bird population without accurate population data in all environments.
Which brings us back to the beginning, are domestic cats wild animals or companions?
Ingrid R. Niesman MS PhD is the director of the SDSU Electron Microscope Imaging Facility at San Diego State University. She graduated from Utah State University and earned her master’s degree from the University of Illinois-Urbana-Champaign. After 30 years of technical electron microscopy, cell biology, neuroscience and infectious disease research, Dr Niesman completed his PhD in the UK at the University of Sunderland. His work experience includes time at LSU Medical School, Washington University, UAMS in Little Rock, UCSD, TSRI and a postdoctoral year at CALIBR in La Jolla, CA. She has worked for at least two members of the National Academy of Science and is credited with over 50 publications. She can be reached at iniesmanphd@gmail.com
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