When the Wildlife Center of Virginia, a hospital for native wild animals, took a close look at a decade’s worth of admissions records, it found the unsurprising culprits behind many of the thousands of injuries and deaths: cats.
More startling was the sheer number of native species — more than 80 — that felines had preyed upon and killed.
“It goes beyond the common perception that outdoor, free-roaming cats just attack mice and rats,” said David McRuer, the director of veterinary services at the center and the lead author of a note on the records that was published last week in the Journal of Wildlife Management.
The authors looked at close to 21,000 records of patients admitted to the center, in the central Virginia city of Waynesboro, from 2000 to 2010. Of those, almost 3,000 had been injured by cat attacks — some 14 percent, divided about evenly between birds and small mammals. Among the cat victims were mourning doves, blue jays, cottontail rabbits, southern flying squirrels and rarer animals, such as purple gallinules, a kind of water bird. Larger species such as ducks also turned up, and even a kestrel, a kind of falcon.
“It’s impressive that cats can take them down,” McRuer said of the kestrel, adding that few previous studies have documented the number of species affected by cat predation.
The researchers said they took a conservative approach, counting only mammals and birds that had been found either in the mouths of cats or brought by cats to their owners.
The study adds more fuel to a tense fight between conservationists, who view free-roaming cats as super-predators that spread disease and devastate wildlife, and cat advocates who argue that popular programs to neuter feral cats are the most humane way to handle them.
Rebekah DeHaven, the senior attorney and associate director of humane law and policy at Alley Cat Allies, which promotes trap-neuter-return programs, commended the center’s efforts to classify the cases. But she said the study did not go far enough.
“From the information shared in the study, there is no way to know how many of the mammals or birds labeled as having been subject to interactions with cats were either ill or injured, by misfortune or by another predator, prior to being found by a cat, leaving open a wide range of other possible ailments that would have led to their death even without a cat’s presence,” she said.
Cats’ proximity to people, she argued, also means attacks to wildlife that occur near humans might be overrepresented in the data.
But the number of animals actually killed by cats is likely much higher, McRuer said. Many of the animals admitted to the center with unknown causes of trauma had injuries consistent with cat attacks but weren’t counted because cat interactions were not observed, he said. And cat predation also extends to reptiles and amphibians, which weren’t part of the original study but whose admission records McRuer and other researchers are examining now.
“It’s not surprising,” said Peter Marra, co-author of the recent book “Cat Wars: The Devastating Consequences of a Cuddly Killer.” “It’s really just the tip of the iceberg that we’re seeing in this paper.”
Marra, head of the Smithsonian Migratory Bird Center, said rehab centers all over the country find the same thing. “The numbers of animals that are brought into rehab centers pale in comparison to those that never make it,” he said. “The evidence against cats and their impact on biodiversity is just overwhelming and yet we still allow them to persist on the landscape.”
Marra co-authored a 2013 study that found cats killed at least 1.3 billion birds and at least 6.3 billion mammals every year in the United States. Some critics have questioned the accuracy of those numbers, saying they were based on studies of smaller, individual ecosystems that were improperly extrapolated to make regional generalizations.
Cory Smith, director of companion animal public policy at the Humane Society of the United States, said habitat loss and other human-related causes affect bird and wildlife populations. She said the Humane Society, which also advocates for wildlife, shares concerns about cats but does not support using lethal measures to deal with them.
“Cats are one of many, many factors in all of this,” she says. “Right now these types of studies are being promoted in a way that is not helpful, because they often make this very naive calling for the elimination of cats from the landscape without understanding what that would entail.”
McRuer’s data show that cats can do great damage to wild animals, even if they don’t finish the job. Some 80 percent of birds and 70 percent of the mammals admitted to the rehab center had to be euthanized. Wounds are a primary cause of death, but many animals die of infections caused by the bacteria that cats can pass on to wildlife through their teeth and claws, McRuer said.
“One of the take home messages from that is that when people find an animal caught by a cat and are able to free it from the cat and let it go again, the chances of that animal surviving in the wild are very low,” he says.
Smith said conservationists should collaborate more with animal welfare groups in dealing with the issue.
“We don’t defend cats to the point of saying ‘Nothing else needs to be done.’ Nobody would agree with that,” she said. “There are 30 to 40 million community cats out there on the landscape, and we estimate that about 2 percent of them are sterilized, so there is a lot of work to do.”
Marra says that cats aren’t the root of the problem — they are just doing what comes naturally to them. “It’s a problem with humans and our ability to responsibly care for our animals,” he says. “We turn them into pests based on whether or not we choose to let them outside.”