US Domestic Cats Killing Birds And Mammals In Record Numbers, According To Smithsonian
January 29, 2013

US Domestic Cats Killing Birds And Mammals In Record Numbers, According To Smithsonian

Lawrence LeBlond for - Your Universe Online

Just a week ago we reported that a New Zealand economist was looking for a way to rid the island of its cat infestation, with claims that the curious critters were responsible for millions of bird kills annually, leaving the country with a big dent in its native bird population.

While many were outraged by the seemingly unwarranted call out for residents to not replace their dying feline family members, it seems there may have been some truth behind the madness, at least here in the United States that is.

A recent study by researchers at the Smithsonian, published in the journal Nature Communications, has found evidence that domestic cats in the US kill upwards of 3.7 billion birds and more than 20 billion mice, voles and other small mammals every year.

The study also found that this feline frenzy is responsible for a bigger animal-elimination rate than other well-known factors such as habitat loss, agricultural chemicals and hunting. Even while a large number of these small critters are meeting their makers via building-crashes, car-squashings, and poisonings, the number being killed by the family pet could be far greater.

By nature, all cats are blood thirsty predators, and have been named among the top 100 worst invasive species in the world. Cats are also responsible for many island extinctions, as they were companion travelers with sailors for centuries, wiping out native habitats in many places that originally had no natural predator, when they arrived on these oceanic hideaways. In all, cats claim 14 percent of modern bird, amphibian and mammal island extinctions.

As far as mainland USA, there are some exceptions to the rule, said study authors. While domestic cats are responsible for a massive number of bird and mice kills every year, it is important to note that the majority have come from feral cats and strays–not house cats.

The findings come from researchers working from the Smithsonian´s Migratory Bird Center and the US Fish and Wildlife Service (FWS) Center. They assembled a systematic review of every US-based cat predation study known in scientific literature. The compiled study includes data from the 48 contiguous US states, but not Alaska or Hawaii.

The results are shocking, but real.

The authors, led by Scott Loss at the Smithsonian Conservation Biology Institute in Washington, found that cats with outdoor access, mainly those that are feral or stray, kill between 30 and 47 birds apiece each year, and between 177 and 299 small mammals, according to past studies.

Loss´s team calculated that in the US, there are some 84 million cats owned as pets–it is likely that several million of these are strictly indoor cats and were not taken into consideration. The team also estimated that there are between 30 and 80 million “unowned” cats in the US.

With those numbers in mind, it is easy to come up with a good estimate of how many creatures in all are being slaughtered by the wrath of the pussycat. The study found that anywhere between 1.4 and 3.7 billion birds lose their lives each year to cats in the US. About 33 percent of these birds being killed are non-native species.

The team also estimated that between 6.9 and 20.7 billion small mammals become meals for cats. In urban settings, most of these mammals are pesky rats and mice. But in the more rural areas, animals such as rabbits, squirrels, and shrews become dinner entrees. Just under 70 percent of those critters are killed by unowned cats--three times the number house cats prey upon.

It is possible that domestic cats are also impacting the reptile and amphibian populations; however there are no figures for that area, as studies have been limited in the US. But based on data from Europe, Australia and New Zealand, the authors believe there could be as many as 822 million reptiles and 299 million amphibians becoming kitty food in the US each year.

"I was stunned," said ornithologist Peter Marra of the Smithsonian's Conservation Biology Institute, one of the study coauthors.

The authors wrote that estimates are much bigger than previously thought, and show that cats "are likely the single greatest source of anthropogenic [man-made] mortality for US birds and mammals."

And “scientifically sound conservation and policy intervention [are] needed to reduce this impact,” they add.

This study was part of a much larger three-year study funded by the FWS to estimate the number of birds being killed each year by predators, chemicals, and collisions with objects such as buildings, wind generators and aircraft.

About a third of the 800 species of birds in the US are endangered, threatened or in significant decline, according to the American Bird Conservancy.

Bird lovers and cat lovers have clashed for years over the issue of whether outdoor cats, not native to the US, should be euthanized or allowed to roam free in managed programs that include neutering. City councils, animal shelters and state wildlife officials have long struggled with the issue as well.

This study is also critical of the Trap-Neuter-Return (TNR) policy advocated by Alley Cat Allies and other supporters of free-roaming cats. The goal of the TNR policy is to gradually reduce the outdoor cat population while avoiding widespread euthanasia policies in animal shelters. Currently, an estimated 4 million cats are euthanized each year in animal shelters across the country, according to the No-Kill Advocacy Center in Oakland, California.

But the study authors said the TNR policy is "potentially harmful to wildlife populations" because it leaves so many predators in the wild. The authors also say the policy is often put in place by cities and counties without "widespread public knowledge" and without studies on the impacts of large feral cat populations on the environment.

Cat lovers everywhere will likely not change their belief that cats are not the real threat behind mass bird deaths across the US.

"Human impact is the real threat" to birds, Becky Robinson, president of Alley Cat Allies, told USA Today. She said the TNR policy is growing because people see it as a way to protect birds without killing cats. "This is not Sophie's Choice, this is not the American people voting to kill one animal over another."

George Fenwick, president of the American Bird Conservancy, said it´s not about cats vs. birds, but about "a runaway and invasive population of cats" that are killing too many birds.

He said the study gives his side powerful evidence that the TNR policy is not working, and aims to push for more responsible cat-ownership policies around the country. He said too many people have been led to believe that cats can live outdoors without harm to the environment. The numbers revealed in this study, he said, “will undue a lot of previously thought things.”