The Animal Doctor

DEAR DR. FOX: A colleague passed along one of your recent columns. In “Questioning Causes of Bird Mortality," a writer claims that the estimates of bird mortality (1.3 to 4 billion birds killed per year) from cats “are bogus and from a discredited study.”

This is a common refrain from opponents of keeping cats exclusively contained. As you can probably guess, it is also false. I invite you to reach out to the study’s authors (Pete Marra, Scott Loss, Tom Will), each employed at respected institutions, to determine the validity of the claim.

The single greatest indicator that the study has not been discredited is that there is no published study making any such statement. On the contrary, a similar study (Ballash, et al., 2013) conducted in Canada came to the same conclusion. Furthermore, if you break down the numbers, the estimates are really not extreme at all.

There are so many cats wandering outdoors, and each of them kills between x and y numbers of birds each year. The estimate seems far-fetched only because there are so many outdoor cats. -- Grant Sizemore, American Bird Conservancy, Washington, D.C.

DEAR G.S.: Peter Marra, one of the authors of this falsely disputed cat predation and bird mortality study, which reflects the current anti-science sentiment in society today, sent the following statement:

"Our study has in no way been discredited by our peers. It is, of course, disliked by outdoor cat advocates because of the inconvenient truth it uncovers. They claim it is discredited with the hopes that this idea will spread, but they can't point to a publication or paper that discredits the study.

"We stand by the mortality estimates and by our statement that cats directly kill more birds in the United States than any other source of direct anthropogenic mortality. To be clear, habitat destruction is still the most significant cause of bird declines over time, but cats far exceed any other cause of direct mortality, and that's a problem we should be able to reverse." -- Peter Marra, Takoma Park, Maryland


United Pet Group, a division of Spectrum Brands Inc., is voluntarily recalling multiple brands of packages of rawhide dog chew products that were distributed to retail outlets and sold online in the United States.

Manufacturers in Mexico, Colombia and Brazil were using a quaternary ammonium compound mixture as a processing aid in the manufacturing of rawhide chews. The compound is an anti-microbial chemical that is approved for cleaning food-processing equipment, but it has not been approved in the U.S. as a processing aid in the production of rawhide chews for dogs.

The primary complaint received from consumers was that the affected product had an unpleasant odor. Diarrhea and vomiting were also reported. Exposure to quaternary ammonium compounds through direct ingestion may cause the following symptoms in dogs: reduced appetite and gastric irritation, including diarrhea and vomiting. These symptoms may require treatment by a veterinarian, depending on severity.

All of the dog chew products included in the voluntary recall identify an expiration date ranging from June 1, 2019 through May 31, 2020. The recalled brands include American Beefhide, Digest-eeze, Healthy Hide Good-n-Fit brand and Healthy Hide Good-n-Fun brand. If you have these products, contact the United Pet Group consumer affairs team at 1-855-215-4962.

Another recall was subsequently announced on dog chews containing this chemical-treated rawhide for several private-label brands: Companion, Dentley’s, Enzadent or Dentahex, Essential Everyday, Exer-Hides, Good Lovin’ or Petco, Hill Country Fare and Priority Pet.

For more details, visit

(Send all mail to or to Dr. Michael Fox in care of Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

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