8 Ways Domestic Cats Are a Serious Threat to Nature

Who doesn’t love a Grumpy Cat video or sneezing kittens? But offline, domestic cats represent a threat to the natural world—and a much more serious one than you might think. Here’s a look at some of the environmental risks cats pose that might encourage you to keep Kitty inside.

1. ISLANDS ARE VULNERABLE TO FELINES …

Thanks to their isolation, islands generally boast high levels of biodiversity and endemic species found nowhere else. Island species evolve based on a very specific set of circumstances; on islands without large predators, for example, some birds lose the ability to fly because they simply don’t need it. This makes the cat problem particularly acute on islands, where free-ranging cats have caused or contributed to 33 of the modern bird, mammal, and reptile extinctions recorded by the International Union for Conservation of Nature (IUCN) Red List.

2. … BUT SO ARE CONTINENTS.

Felines down under have become a major pain: A recent study in Biological Conservation finds that feral cats roam 99.8 percent of Australia. This means that at any given time, there are somewhere between 2.1 to 6.3 million cats ranging around the continent, ignoring any and all posted signs about environmentally protected areas. Since Australia is the only continent other than Antarctica where wildlife evolved without wild cat species, its wild creatures are particularly vulnerable. John Woinarski of Charles Darwin University, the deputy director of the National Environmental Science Programme’s Threatened Species Recovery Hub and the study’s co-author, tells mental_floss, “Australia has the worst record of extinctions of native mammal species over the last two centuries.” Approximately 30 species have gone extinct. “Introduced cats were a significant factor in most of these extinctions, and feral cats continue to be one of the most serious threats to many of Australia’s threatened animal species,” he says.

In fact, some of Australia’s endangered species survive only within specialized cat-proof exclosures or on cat-free islands. According to a 2012 government plan, species at risk include the endangered woylie, night parrot, bridled nail-tail and black-footed rock wallabys, and the vulnerable greater bilby. To combat the feline threat, the country’s Threatened Species Commission recently launched an ambitious plan to cull feral cats using baits, traps, and even trained cat-finding dogs.

2. THEY’VE TAKEN OVER NEW ZEALAND.

New Zealand has a number of rare endemic species, including the iconic flightless kiwi. The island also has an estimated 2.5 million feral cats. It’s a problematic equation. Cats have already contributed to the extinction of nine native bird species and have affected 33 endangered bird species. The National Cat Management Strategy Group (NCMSG), which includes the Royal New Zealand Society for the Prevention of Cruelty to Animals, Local Government New Zealand and the Morgan Foundation, set a goal of eliminating feral cats by 2025. Government officials have been quick to point out that no one is limiting cat ownership and the former Prime Minister, John Key, has a pet cat.

 "We all agree on what we are trying to achieve,” Geoff Simmons, spokesperson for Morgan Foundation, an NCMSG partner, told Radio New Zealand, “which is making sure all cats are loved pets and are looked after well, and that we minimize the stray and feral population and ensure that the cats that we do own have the least possible impact on our environment."

The government also plans to eliminate all invasive vertebrate predators, including rats and brushtail possums, by 2050. Worldwide, more than 1,000 islands have been cleared of invasive species, including more than 100 around New Zealand. But the largest island ever successfully cleared, Australia’s Macquarie Island, is only about 49 square miles; in contrast, New Zealand is 103,483 square miles. To accomplish this daunting task, the government will turn to new methods, including drones and genetic biocontrol.

4. THE U.S. HAS A CAT PROBLEM TOO.

In the United States, an estimated 60 to 100 million cats range free, and the number of domestic cats has tripled during the past 40 years. Scientists from the Smithsonian Institution and U.S. Fish and Wildlife Service estimate that domesticated cats—both free-roaming pets and feral—kill as many as 4 billion birds and 22 billion small mammals in the U.S. each year. This makes them “likely the single greatest source of anthropogenic mortality for U.S. birds and mammals,” according to the Smithsonian. While controlling feral cats poses a daunting problem, simply keeping pet cats indoors at least reduces the slaughter. The Humane Society of the United States has developed tips to help indoor cats stay happy, and suggest that you always neuter even indoor animals, because…

5. CATS REPRODUCE LIKE RABBITS (IN A MANNER OF SPEAKING).

Female cats can reproduce as young as four months old, and on average have two to three litters per year of four to six kittens each. One cat can produce as many as 100 kittens in her lifetime, and one pair of cats and their kittens can account for 420,000+ kittens in just seven years (it’s an exponential thing).

6. THEY CARRY DISEASES.

Peter Marra, director of the Smithsonian Migratory Bird Center and co-author of Cat Wars: The Devastating Consequences of a Cuddly Killer, tells mental_floss that cats are known to carry plague, rabies, and the parasite Toxoplasma gondii. All are zoonotic diseases, carried by animals and capable of jumping to people. Toxoplasma gondii only reproduces in cats, Marra said, producing virtually indestructible oocysts—cysts containing a zygote formed from an egg and sperm. “They persist for years, in frozen soil, in saltwater environments. In the U.S., about 20 percent of the human population is infected, and globally, about a third of the population.” There is no cure.

While most infected people seem to have no symptoms, recent research links the parasite with behavioral changes, including depression and bipolar disorder, Marra reports. For example, one recent study showed infection causes disruption of a major neurotransmitter in the brain. Infections in pregnant women can cause death or serious health issues in the fetus; the parasite damages the eyes of some 3000 infants in the U.S. each year. Toxoplasmosis can cause fever, fatigue, headaches, blindness, and, in people with compromised immune systems, death. Like a ticking time bomb, the parasite can hide in brain tissue, putting an infected person at risk if the immune system later becomes compromised.

Toxoplasmosis also affects wildlife, representing a serious threat to highly endangered Hawaiian monk seals and to sea otters.

7. CAT OWNERS ARE IN SERIOUS DENIAL.

Despite the evidence lined up against cats, pet owners have a hard time accepting that their felines may causing problems. In the UK, which has more than 10 million domestic cats, a recent study found that cat owners did not recognize the risk their pets pose to wildlife. “Cat owners failed to perceive the magnitude of their cats' impacts on wildlife and were not influenced by ecological information,” the study’s authors concluded.

Solving the problem of cat predation on wildlife obviously will require cooperation of pet owners. So it’s important to note: While one individual cat’s predation may not be an issue, the sheer number of cats equals a big problem. This is especially true since predation by cats is often not a normal ecosystem interaction (in other words, domestic cats are not part of a healthy natural ecosystem).

8. IF YOU’RE FEELING DEFENSIVE, REMEMBER THE CASE OF THE MISSING WREN.

In Cat Wars, Marra tells the story of Stephens Island, off the south island of New Zealand, where cats drove an endemic, flightless wren to extinction in—wait for it—roughly one year. A lighthouse keeper named David Lyall arrived on the island in January 1894. A pregnant female cat arrived about the same time, likely the island’s first feline. An amateur ornithologist, Lyall studied the dead birds that this free-roaming cat brought to the lighthouse. Based on his prepared specimens, noted ornithologist Walter Rothschild described a new species, the Stephens Island Wren. Unfortunately, by that time the bird had disappeared. Subsequent lighthouse keepers began killing feral cats and had the island once again cat-free by 1925—but it was too late for the endemic wren. 

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13 Facts About Opossums
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Opossums, which include the roughly 100 species in the order Didelphimorphia, are some of the most misunderstood animals in the Americas. They’re often thought of as dimwitted, dirty creatures whose most impressive trick is acting like roadkill. The truth is just the opposite: Opossums are smarter, cleaner, and more beneficial to humans than many of their woodland neighbors. Read on for more opossum facts.

1. OPOSSUMS AND POSSUMS AREN’T THE SAME ANIMAL.

In North America, opossum and possum describe the same thing, but in Australia the word possum refers to a completely different animal. Among the most well known of their respective types are the Virginia opossum and the brushtail possum. Both are small to medium sized, omnivorous marsupials, but the similarities end there. The possum looks like a cute cross between a squirrel and a chinchilla and it belongs to a different order than the North American mammal that shares (most of) its name. Despite the potential for confusion, possum is accepted as the shortened version of opossum in this part of the world (and if you see the word possum in this list, you can assume it’s referring to the animal from the Americas).

2. THEY’RE THE ONLY MARSUPIALS FOUND NORTH OF MEXICO.

Marsupials—mammals that carry and nurse their young in pouches—are absent from much of the world, and in Canada and the United States opossums are the sole representatives of the group. Like other marsupials, mother possums give birth to tiny, underdeveloped offspring (called joeys) that immediately crawl into a pouch where they live and nurse during their first months of life. Only once they’ve grown big and strong enough do they venture out, transitioning between their mother’s back and the warmth of the pouch until they mature into adults.

3. THEY CAN’T CHOOSE WHEN THEY PLAY DEAD.

Possum playing dead.
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Perhaps the most famous characteristic of the opossum is its tendency to play dead in front of predators. When the animal experiences intense fear in the face of danger, it seizes up and flops to the ground where it can remain for hours staring blankly ahead and sticking out its tongue. It’s an impressive defensive mechanism, but its effectiveness can’t be chalked up to the possum’s acting skills. Possums have no control over when they play dead or for how long they do it: The comatose-like state is an involuntary reaction triggered by stress.

4. AN OFFENSIVE ODOR SELLS THE PERFORMANCE.

A picture of a possum playing dead doesn’t really do it justice. To get the full experience, you need to be standing over to it to smell the putrid odor it emits when pretending to be a corpse. The smelly substance it secretes from its anus is just one more reason for foxes and bobcats to look for their dinner elsewhere.

5. THEY SLOW THE SPREAD OF LYME DISEASE.

Even if possums aren’t the cutest creatures in the forest, they should be a welcome addition to your backyard. Unlike other mammals that carry ticks, and therefore spread Lyme Disease, possums gobble up 90 percent of the ticks that attach to them. According to the National Wildlife Federation, a single possum consumes 5000 of the parasites per tick season. That means the more possums that are in your area, the fewer ticks you’ll encounter.

6. THEIR MEMORIES ARE SURPRISINGLY SHARP.

Possum looking up at table.
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Opossums have impressive memories—at least when it comes to food. Researchers found that possums are better at remembering which runway led to a tasty treat than rats, cats, dogs, and pigs. They can also recall the smell of toxic substances up to a year after trying them.

7. THEY’RE IMMUNE TO MOST SNAKE VENOM.

While most animals look at a snake and see danger, a possum sees its next meal. The animals are immune to the venom of nearly every type of snake found in their native range, the one exception being the coral snake. Possums take advantage of this adaptation by chowing down on snakes on a regular basis.

Researchers have been trying to harvest possums’ antivenom powers for decades. A few years ago, a team of scientists made progress on this front when they recreated a peptide found in possums and and found that mice given the peptide and rattlesnake venom were successfully protected from the venom’s harmful effects.

8. THEY ALMOST NEVER GET RABIES.

While possums aren’t totally immune to rabies (a few cases have been documented), finding a specimen with the disease is extremely unlikely. Marsupials like possums have a lower body temperature than the placental mammals that dominate North America—in other words, their bodies don’t provide a suitable environment for the virus.

9. THEIR TAIL ACTS AS A FIFTH APPENDAGE.

Baby opossum hanging from a tree branch by its tail.
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Opossums are one of a handful of animals with prehensile tails. These appendages are sometimes used as an extra arm: They can carry grass and leaves for building nests or grip the sides of trees to provide extra stability while climbing. Baby possums can even use their tails to hang from branches upside down as they’re often depicted doing in cartoons. But it’s a myth that possums sleep this way: Their tails are only strong enough to hold them for a short amount of time.

10. THEY’RE CONSTANTLY SELF-GROOMING.

Thanks to their whole acting-and-smelling-like-a-corpse routine, opossums aren’t known as the most sanitary animals in nature. But they take cleanliness seriously: The Washington Department of Fish and Wildlife writes that possums, like housecats, use their tongue and paws to groom themselves frequently and thoroughly. Possums largely lack sweat glands, and this behavior is believed to help them cool down. It also has the added effect of rendering them odorless (when they’re not secreting stinky predator-repellant, that is).

11. THEIR EYES AREN’T TOTALLY BLACK.

Close-up on opossum's face.
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One of the opossum’s most recognizable features is its pair of opaque eyes. Opossum eyes do have whites and irises, but because their pupils are so large, their eyes appear completely black from a distance. The exaggerated pupil dilation is thought to help the nocturnal animals see after the sun goes down.

12. THEY’RE SOCIAL CREATURES.

It was long assumed that opossums like to keep to themselves, but a study published in the journal Biology Letters suggests they have a social side. Researchers at the Federal University of Pernambuco in Recife, Brazil observed some possums in captivity sharing dens even if they weren’t mates. In one case, 13 white-eared opossums of various age groups were cohabiting the same space. The scientists suspect that male and female possums living in the wild may even build nests together as a way to trigger the female’s reproductive hormones.

13. THEIR REPRODUCTIVE SYSTEMS ARE COMPLICATED.

The way it gives birth and raises its young isn’t the only thing that’s interesting about the opossum's reproductive life. Females have two vaginal tracts and two uteri, and males in turn have a forked or bifurcated penis. This is fairly typical for marsupials, but when European colonizers first landed in North America centuries ago, they didn’t know what to make of the confusing genitalia. One explanation they came up with was that male opossums impregnated females through the nose.

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Hero Crayfish Cheats Death By Removing Its Own Claw to Escape Pot of Boiling Water
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There remains a perpetual debate over the ethical consequences of taking a crustacean and boiling it alive. In early 2018, Switzerland actually made it illegal to give living lobsters a scalding hot bath. (Instead, chefs are expected to stun them electronically before submersion.) Scientists can’t reach a conclusion over whether decapods feel pain—or if we can even define what that means for them.

While humans argue, some clawed sacrifices are taking action. A crayfish filmed by a Facebook user in China is making the internet rounds and being hailed as a hero after taking dramatic measures to escape a boiling pot of water.

In the footage, the crayfish appears to be unable to extricate its left appendage from a bubbling vat of doom. Rather than succumb, the crayfish uses its right claw to sever its compromised claw and scurry off. At 11 seconds, it’s the best summary of a Saw film possible.

“Juike,” the user who originally posted the video to the Weibo social media site, says he has taken the crafty invertebrate home and put him in an aquarium as a pet. The tiny survivalist may even regrow his lost limb, as crawfish are able to do, although it might not reach its former size.

Crayfish are in inherent danger of being turned into soup in China, where specialty restaurants devoted to their preparation are popping up. Some observers believe their popularity is due to diners having to step away from phones and social media in order to use both hands to peel away at their shells.

[h/t BBC]

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