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A feral cat, just trying to get by. Photo: Topsynette

There are so many ways for a little bird or squirrel to die these days–they can be squished by cars, splattered into buildings, run over by bulldozers, poisoned or even shot. But if you have ever had to clean up a mangled “present” left on your doorstep by a kitty, you’ll know that little creatures can also be killed by pets.

Cats in particular have earned a nasty reputation for themselves as blood thirsty killers of wildlife. They have been named among the top 100 worst invasive species (PDF) in the world. Cats have also earned credit for countless island extinctions. Arriving onto the virgin specks of land alongside sailors, the naive native fauna didn’t stand a chance against these clever, efficient killers. All said, cats claim 14 percent of modern bird, amphibian and mammal island extinctions. But what about the mainland?

A recent study aimed to find out just that. Now the stats are in, and it’s much worse than we thought. But before bird lovers rush to declaw pets, the study’s scientists also found that feral cats and strays–not house cats–are responsible for the majority of the killings.

To arrive at the new findings, researchers from the Smithsonian’s Migratory Bird Center and the U.S. Fish and Wildlife Center assembled a systematic review of every U.S.-based cat predation study known in the scientific literature (excluding Hawaii and Alaska). Based on figures the authors verified as scientifically rigorous, they statistically quantified the total bird and small mammal mortality estimate caused by cats, further breaking the categories down into domestic versus unowned cats, that latter of which the authors define as barnyard kitties, strays that receive food from kind humans and cats that are completely wild. 

Their results paint a grim picture for wildlife. In a paper published today in Nature Communications, they write that between 1.4 to 3.7 billion birds lose their lives to cats each year in the United States. Around 33 percent of the birds killed are non-native species (read: unwelcome). Even more startlingly, between 6.9 to 20.7 billion small mammals succumb to the predators. In urban areas, most of the mammals were pesky rats and mice, though rabbit, squirrel, shrew and vole carcasses turned up in rural and suburban locations.  Just under 70 percent of those deaths, the authors calculate, occur at the paws of unowned cats, a number about three times the amount domesticated kitties slay.

Cats may also be impacting reptile and amphibian populations, although calculating those figures remains difficult due to a lack of studies. Based upon data taken from Europe, Australia and New Zealand and extrapolated to fit the United States, the authors think that between 258 to 822 million reptiles and 95 to 299 million amphibians may die by cat each year nationwide, although additional research would be needed to verify those extrapolations.

These estimates, especially for birds, far exceed any previous figures for cat killings, they write, and also exceed all other direct sources of anthropogenic bird deaths, such as cars, buildings and communication towers.

The authors conclude:

The magnitude of wildlife mortality caused by cats that we report here far exceeds all prior estimates. Available evidence suggests that mortality from cat predation is likely to be substantial in all parts of the world where free-ranging cats occur. 

Our estimates should alert policy makers and the general public about the large magnitude of wildlife mortality caused by free-ranging cats.

Although our results suggest that owned cats have relatively less impact than un-owned cats, owned cats still cause substantial wildlife mortality; simple solutions to reduce mortality caused by pets, such as limiting or preventing outdoor access, should be pursued.

The authors write that trap-neuter/spay-return programs–or those in which feral cats are caught, “fixed,” and released back into the wild unharmed–are undertaken throughout North American and are carried out largely without consideration towards to native animals and without widespread public knowledge. While cat lovers claim that these methods reduce wildlife mortality by humanely limiting the growth of feral colonies, the authors point out that the scientific literature does not support this assumption. Therefore, such colonies should be a “wildlife management priority,” they write. They don’t come out and say it but the implication is that feral cat colonies should be exterminated.

But feral cats, some animal rights advocates argue, are simply trying to eke out a living in a tough, unloving world. As the Humane Society explains, simply removing the cats may not be the most efficient means of solving the problem because cats that are inevitably left behind repopulate the colony, surrounding colonies may move in to replace the old and “the ongoing abandonment of unaltered pet cats…can also repopulate a vacated territory.” Feral cats, after all, are the “offspring of lost or abandoned pet cats or other feral cats who are not spayed or neutered.” Targeting irresponsible humans may provide a different solution, although spay/neuter laws are controversial. 

In Washington D.C. alone, for example, there are more than 300 known feral cat colonies. Wildlife are victims of this problem, but feral cats are too as conditions for survival are tough. And as with so many other environmental banes, the root of the problem neatly traces back to a single source: humans. As the authors write in their paper, feral cats are the single greatest source of anthropogenic (human-driven) mortality for U.S. birds and mammals.

Incidentally, the Humane Society will host World Spay Day on February 26. Find an event for your furry friend to attend, or even host a spaying party yourself. 

New research indicates that the influenza virus can jump from humans to pet animals, raising the possibility of dangerous mutations. Image via Wikimedia Commons/Dave Scelfo

As autumn arrives, the approach of flu season is a real concern. Last year, thousands of people suffered from symptoms including a high fever, chills and fatigue—classic signs of the flu. Some 2,374 people in the United States were hospitalized for influenza during the last flu season—an incentive for many of us to get an annual flu vaccine, to avoid both getting sick and potentially passing on the flu to family members.

A group of veterinarians at Oregon State and Iowa State Universities is now looking into the risk of flu for an unexpected population that doesn’t have access to flu shots: dogs, cats and other household pets. “We worry a lot about zoonoses, the transmission of diseases from animals to people,” said Christiane Loehr, a professor at the OSU College of Veterinary Medicine. “But most people don’t realize that humans can also pass diseases to animals, and this raises questions and concerns about mutations, new viral forms and evolving diseases that may potentially be zoonotic. And, of course, there is concern about the health of the animals.”

We’re pretty well acquainted with zoonoses—diseases that can move from animals to humans—because of the high profile transmissions of the influenza strains H1N1 (“swine flu“) and H5N1 (“bird flu”) from animals in recent years. But, as it turns out, many diseases can also act as so-called reverse zoonoses, or anthroponoses, contagiously jumping from humans to other animals. This appears to be the case for H1N1: The researchers have discovered 13 cases in which H1N1 seems to have been passed from humans to pet cats, some of which ultimately died from the disease.

The first recorded instance, described in an article published by the team in Veterinary Pathology, took place in Oregon in 2009. While a cat owner was hospitalized with H1N1, both of her cats (which stayed indoors and had no contact with other sick people or animals) came down with flu-like symptoms and eventually died. A postmortem analysis of their lungs and nasal cavities turned up the H1N1 virus.

In the years since, the research team has turned up 11 more cats, one dog and even some ferrets that seem to have been infected with H1N1 due to human contact. The animals’ flu symptoms—respiratory disease and, for some, eventual death—resemble the same symptoms suffered by humans who encounter severe strains of the flu.

For the roughly 100 million U.S. households that have a cat or dog, this news might trigger immediate concern, and the researchers say that anyone experiencing flu-like symptoms should distance themselves from their pets in much the same way they would from other people. Since this area has been the subject of so little attention, they say that there might be many more undiscovered cases of the flu jumping from humans to pets. “It’s reasonable to assume there are many more cases of this than we know about, and we want to learn more,” Loehr said.

Realistically, though, the actual number of animals infected is quite small when compared to the population at large. The bigger worry is that the flu virus could mutate into a more dangerous form as it is transmitted from humans to animals. “Any time you have infection of a virus into a new species, it’s a concern, a black box of uncertainty,” Loehr noted.

The influenza virus in particular mutates notoriously easily, with entire segments of its genome changing within a generation. The reason that H1N1 was declared a “national emergency” in 2009 was because it was a strain that mutated when it jumped from pigs to humans, raising the possibility that it had taken on a more deadly form that could be transmitted more easily between people.

In a worst-case scenario, the pets we keep in our homes could serve as the same type of mutation-inducing vector—the flu could be passed from human to pet, mutate into a more dangerous form, and then potentially affect both humans and other animals. “In terms of hosts and mutations, who’s to say that the cat couldn’t be the new pig?” Loehr asked. “We don’t know for sure what the implications might be, but we do think this deserves more attention.”

Snow leopards live in the remote mountains of countries such as Bhutan, China, India, Mongolia and Nepal. They are endangered—a mere 4,000 to 6,000 individuals are spread out over Central Asia—and live solitary lives, usually active just at dawn and dusk. Coupled with their exceptional camouflage, this makes them notoriously elusive—although they figure largely in the mythology of many Asian cultures, wild snow leopards weren’t even caught on camera until the 1970s.

Now, for the first time, a team of researchers from the Snow Leopard Trust and Panthera, a wild cat conservation organization, have captured video of a wild snow leopard mother and cubs in a den, seen above. “This is incredible. Snow leopards are so rare and elusive that people often talk about them as ‘ghosts’ of the mountains,” said Brad Rutherford, Executive Director of the Snow Leopard Trust. “This is the first documented visit of a den site with cubs, and thanks to this video we can share it with the world.”

The search began back in 2008, when an team of scientists affixed GPS collars to several snow leopards encountered in Mongolia’s Gobi Desert. Then, this past May, a pair of females from the study began restricting their movements to a smaller area, indicating they were preparing to give birth. Researchers tracked the VHF signals emitted by the collars through steep mountain outcroppings, coming upon a pair of dens located less than four miles apart in the Tost Mountains on June 21st.

One of the snow leopard cubs discovered in Mongolia’s Tost Mountains. Photo via Panthera/Snow Leopard Trust

“As we stood outside the den we could hear the cub and smell the cats but not see anything inside the den,” said Panthera scientist Orjan Johansson. He and colleagues acted quickly, taping a camera to their antenna pole and extending it over the ledge blocking the den entrance. The footage captured shows a female leopard looking up at the camera, keeping a protective paw over her cub.

At the second den—a narrow crack in a cliff wall—the scientists discovered that the mother was away hunting, leaving her two male cubs unattended, seen below. “This was an unprecedented opportunity,” said Rutherford. “We wanted to be as careful as possible and only take the most pressing data.” The team quickly weighed, measured, photographed and collected hair samples from the cubs, which allowed genetic testing that confirmed sex and other information. More pictures of the cubs are available at Panthera’s photo gallery.

The team also implanted microchip ID tags—each of which are roughly the size of a grain of rice—under the cubs’ skin, which will allow the researchers to identify the animals as part of future conservation projects. After leaving, they tracked signals from the mother’s VHF collar to ensure that she returned to the den, and they note that she is still with the cubs now. The researchers do not plan to visit the dens again, so as to limit future disturbance to the cubs.

The team says that the information collected will be extremely valuable in future attempts to conserve the endangered species. Remarkably little is known about snow leopard behavior, and most of what we understand about the rearing of cubs is known from studying the animals in a zoo environment. Until know, scientists had to speculate about typical litter sizes, cub weights, sex ratios and survival rates.

“Knowledge about the first days and weeks of life is vital to our understanding of how big cat populations work, and how likely it is for a newborn to reach adulthood and contribute to a healthy population,” said Panthera’s Howard Quigley. “A valid conservation program requires such information, which this new development in snow leopard research provides.”

The organization plans to use the microchip ID tags affixed to the cubs to learn about the characteristics of a typical snow leopard upbringing, such as how long the cubs remain in dens, when they being to hunt with their mothers and when they start to venture out on their own. Along with future GPS collaring programs, these data will assist with large-scale conservation efforts across the species’ range.

“We have spent years trying to determine when and where snow leopards give birth, the size of their litters and the chances a cub has of surviving into adulthood,” said Tom McCarthy, director of Panthera’s snow leopard program. “This is one of those exceptional moments in conservation where after years of effort, we get a rare glimpse into the life of an animal that needs our help in surviving in today’s world.”

Cats and earthquakes were popular subjects this year. (image courtesy of flickr user 37prime)

It’s that time of year when journalists and bloggers put together their reviews of the past 12 months. But the list below is unlike any other. You may have noticed that Surprising Science tends to cover science a bit differently than other blogs and publications do. Combine that with a diverse (and, of course, fabulous) readership, and you’ve got an interesting list of most-read stories for the year. (If you’re looking for a more traditional 2011 retrospective, we recommend the lists from Discover, Scientific American and Science.)

#10 Earthquake in Washington, D.C.: On August 23, the Smithsonian offices, along with a good portion of the Northeast, shook due to a magnitude 5.8 earthquake in Mineral, Virginia. In a weird coincidence, I had been researching earthquakes in unexpected places when the quake took place, and so people in my office jokingly blamed me for the incident.

#9 14 Fun Facts About Chickens: Following the earthquake and Hurricane Irene, we took a break from natural disasters with weird chicken facts. My favorite? That a female bird can eject the sperm of a rooster if she decides she doesn’t want his chicks.

#8 The Science Behind the Japanese Earthquake: On the morning of March 11, we woke up to news of a powerful earthquake off the coast of Japan. That shaking, however, would soon be overshadowed by the devastating tsunami and nuclear disaster that followed.

#7 Examining Telecommuting the Scientific Way: Unfortunately this post did not have the result I’d hoped, and I’m still not allowed to telecommute. (But if anyone has been successful in using these arguments, please let us know in the comments below.)

#6 The Secret Lives of Feral Cats: After a study in which scientists tracked feral kitties, we weighed in on the question of whether it was better to trap the cats, spay/neuter them and release them back into the wild or, as some advocate, euthanize any found. The blog came down on the side of catch and release, but we discovered many readers who have a serious hatred for these felines.

#5 The Curious World of Zombie Science: We examined an interesting trend in science, the study of human zombies, including computer models of the spread of the zombie disease, potential ways zombies could be created and how math could save you from a zombie attack.

#4 The Myth of the Frozen Jeans: Levi’s and the New York Times claimed that freezing your jeans would kill the germs that make them smell. Scientists who study bacteria disagree.

#3 Five Historic Female Mathematicians You Should Know: Our list, a companion to a top ten list of historic female scientists, included the creator of the world’s first computer program and a contemporary of Albert Einstein.

#2 Life Without Left Turns: A study that found that intersections constructed to eliminate dangerous left turns were more efficient than traditional intersections added to my convictions that getting rid of left turns would be a good thing. But not all my readers agreed.

And #1 The Glow-in-The-Dark Kitty: A story about Mayo Clinic researchers who created a fluorescing cat as part of their studies on feline HIV, which they hope would lead to insight on human HIV and AIDS, sparked a debate in the comments about the ethics of the research.

Toxoplasma gondii requires the cat digestive system for reproduction, so it hitches a ride in a rat (courtesy of flickr user cobalt123)

The life cycle of the parasite Toxoplasma gondii goes like this: Toxoplasma reproduces inside the intestine of a cat, which sheds the parasite in its feces. Rats then ingest the parasite when they consume food or water contaminated with cat feces. The parasite takes up residence in the rat’s brain and, once the rat gets eaten by a cat, it starts the cycle all over again.

Researchers have known for a few years that a rat infected with Toxoplasma loses its natural response to cat urine and no longer fears the smell. And they know that the parasite settles in the rat’s amygdala, the part of the brain that processes fear and emotions. Now a new study in the journal PLoS ONE adds another bizarre piece to the tale: When male rats infected with Toxoplasma smell cat urine, they have altered activity in the fear part of the brain as well as increased activity in the part of the brain that is responsible for sexual behavior and normally activates after exposure to a female rat.

The double messages of “you smell a cat but he’s not dangerous” and “that cat is a potential mate” lure the rat into the kitty’s deadly territory, just what the parasite needs to reproduce. Scientists still don’t know how the parasite works to alter the brain, though there apparently is a link to production of dopamine, an important neurotransmitter in the systems for decision-making and reward.

How the parasite makes the rat brain do what it needs is a particularly interesting question because rats and cats aren’t the only animals that can become infected with Toxoplasma. There is concern, for example, about the parasite’s effect on sea otters. And grazing livestock can become infected after eating contaminated vegetation. More worryingly, though, is that one-third of humans test positive for exposure to Toxoplasma (the most common ways for humans to come into contact with the parasite is through kitty litter and by consuming undercooked meat). Not only can pregnant women pass on the parasite to an unborn child (putting the child at risk of blindness or mental disability) but recent studies have also found an association between the parasitic infection and increased risk of schizophrenia and obsessive compulsive disorder.

If you’re worried about Toxoplasma, there’s no need to give up your beloved cat, but there are some precautions you can take (and definitely should take if you’re pregnant), as the CDC states:

• Avoid changing cat litter if possible. If no one else can perform the task, wear disposable gloves and wash your hands with soap and warm water afterwards.
• Ensure that the cat litter box is changed daily. The Toxoplasma parasite does not become infectious until 1 to 5 days after it is shed in a cat’s feces.
• Feed your cat commercial dry or canned food, not raw or undercooked meats.
• Keep cats indoors.
• Avoid stray cats, especially kittens. Do not get a new cat while you are pregnant.
• Keep outdoor sandboxes covered.
• Wear gloves when gardening and during contact with soil or sand because it might be contaminated with cat feces that contain Toxoplasma. Wash hands with soap and warm water after gardening or contact with soil or sand.