Strange things happen in island ecosystems, and occasionally—whether by accident, or design—a population of adorable creatures takes over. They draw tourists, can be a little spooky, and sometimes wreak havoc. But you have to admit: they are pretty cute.
1. Ōkunoshima, Japan // Rabbits
Often called Usaga Jima, or Rabbit Island, this place was once a top-secret chemical weapons production site during World War II. Now it’s covered in bunnies. The Poison Gas Museum on Ōkunoshima doesn’t draw as many tourists as the hundreds of rabbits that now roam the streets freely and with little fear of humans (as you can see above). While some suspect the rabbits are descendants of test subjects from the chemical plant, the official story is that schoolchildren left them behind on a visit in the 1970s. With no natural predators on the island, they bred like, well, rabbits.
2. Kauai, Hawaiian Islands // Chickens
The Hawaiian islands are full of odd case studies of introduced species gone wild, but none as cute as the thousands of chickens on Kauai. The feral roosters, hens, and chicks have no natural predators on Kauai, so the population has spun out of control. (The mongooses that keep chickens on the other islands in check aren't found on Kauai.) These chickens have adapted to feed on cat food, garbage, scraps from tourists, and native bugs.
Biologists have taken particular interest in them, as they aren’t your ordinary chickens. A recent genetic study indicates that they may actually be hybrids of chicken ancestors brought from Polynesia hundreds of years ago, and plain old domestic chickens that escaped during more recent hurricanes.
3. Big Major Cay, The Bahamas // Pigs
Pigs big and small spend their days sleeping on the beach and splashing around in the blue waters of this tiny island in the Caribbean. About 20 pigs and piglets now live on the beach, and live at least in part on food from tourists, who frequent the island to swim with them. When a boat comes close to the pigs’ beach (Pig Beach), the animals routinely paddle out for food.
There are many origin stories about how their forebears got there—surviving a wreck, dumped by former owners from a nearby island, planted as a tourist draw. But they’ve been surviving and breeding for years now.
4. Tonawanda Island, New York // Cats
Dozens to hundreds of feral cats live on this island in the river to the north of Buffalo. The 85-acre chunk of land has become a dumping ground-turned-paradise for unwanted felines. While the thought of cats laying claim to their own island to live out their days might sound kind of idyllic, it’s actually a problem. As an island restaurant owner told the TV news, “there’s just too many cats is what it boils down to.”
One area woman made it her mission to get the population under control, raising $16,000 for the cause last year. Operation: Island Cats resulted in the trapping and spaying or neutering of 130 cats, and returning most of them to the island. Kittens were put up for adoption, but most adult cats had already tasted too much freedom.
5. Tashirojima, Japan // More Cats
There are actually about a dozen “cat islands” in Japan. The fishing village on Tashirojima is down to about 100 people, but has hundreds of cats. The story goes that the village once raised silkworms, and cats were introduced to prey on the mice that preyed on the worms. The population grew in the 1800s, as fishermen began to regard the cats as good luck. There are multiple shrines honoring the animals, and visitors can even stay at vacation homes shaped like cats and decorated by famous manga artists.
6. Gough Island // House Mice
Mice can definitely be cute, but this particular tale takes an ugly turn. Sometime in the 1800s, a few tiny house mice wandered off a whaling ship onto an isolated island in the South Atlantic. Mice, which mostly scavenge for insects and seeds, are seemingly not the worst invasive species you could imagine. But then, the mice … changed. They’ve adapted to become top predators thanks to a horrifying trick they picked up—eating seabird chicks alive.
While the chicks are much larger than the mice, they are basically defenseless, and their parents aren’t used to fighting off predators. As the mice became carnivorous, they’ve also grown to be much larger than a typical mouse. These giant killer mice have taken over the small island, endangering its rare seabirds, and leading researchers to plan an eradication program.
7. New Zealand // Sheep
In 1982, New Zealand’s sheep population peaked at something like 22 sheep per person—that’s 70.3 million sheep versus 3.2 million people. That number has dropped significantly these days, due to changing markets, down to a meager 30 million sheep. But that’s still a high, six-to-one sheep-to-person ratio.
New Zealand’s sheep are no freak accident. They are a product of good-old-fashioned colonialism, first dropped off by British explorer James Cook in 1773. Sheep farming became the dominant agricultural industry in New Zealand for 130 years.
8. Miyajima Island, Japan // Deer
This small island in Hiroshima Bay has become a haven for deer, as has the city of Nara on the main island of Honshu. Deer populations are considered a pest in some regions of Japan, but they’ve become a draw at these spots. Hundreds of sika deer wander and lounge casually in the streets, where tourists feed them generously. The Nara deer have even picked up a trick—bow to one, and it will bow back in exchange for food.
9. Lambay Island, Ireland // Wallabies
About 9000 miles from their native Australia, a population of a few dozen wallabies can be seen bounding across this misty island in the Irish Sea. The small, furry relatives of the kangaroo are highly adaptable, and the rocky cliffs, while colder than they like, suit their inclination for rough terrain. The wallabies originally made it to Lambay when the banking family that owns the land decided to raise them in the 1950s and 1960s. The population grew when the Dublin Zoo had a wallaby surplus in the 1980s and introduced a handful on the island.
10. Assateague Island, Maryland/Virginia // Ponies
Famed wild ponies play in the surf on this long and narrow barrier island. They’re actually not wild or ponies, but feral descendants of domestic horses that tend to not grow beyond a certain size. Local lore has it that a group of horses survived the wreck of a Spanish galleon, but most likely they were just brought to the island by colonists in the 17th century. Assateague can be a harsh home, with a limited food supply and frequent storms, but the 300 or so horses that live there have proven themselves to be pretty tough.
11. Runde Island, Norway // Puffins
The rocky cliffs overlooking the Norwegian Sea are home to around 700,000 seabirds, the most famous of which are the puffins. Puffins are adorable and—a rarity on this list—a non-invasive species. The island only has about 100 inhabitants, but is quite popular, as you might imagine, among birdwatchers. If you visit, stay the night in the lighthouse keeper’s house, which has been turned into a self-service cabin.
12. Seal Island, South Africa // Seals
Five acres of rock, 60,000 seals. In fact, there’s pretty much nothing on this island but seals (and seabirds). They roll around on the island all day, being cute, playing, and barking at each other with their little puppy faces. Everyone loves seals. But you know who else loves seals? Great white sharks. Tourists frequent the waters surrounding the island, the “ring of death,” to watch the abundance of great whites, some of which will pop up in order to snatch a seal. The sharks are known for propelling themselves toward the surface and then launching out of the water, seal in jaw.
13. Zao Fox Village, Japan // Foxes
While not exactly an overrun island, this place is too whimsical not to mention. In the mountains of the Miyagi Prefecture on the main Japanese island of Honshu, a sanctuary holds more than 100 roaming foxes of six different types. Although they are wild, visitors can walk among them, and they don’t seem particularly shy.
14. Cayo Santiago, Puerto Rico // Monkeys
About 400 Rhesus monkeys were imported from India to this small research island in 1938, and the population has more than doubled to about 1000 since. No humans inhabit the island, although it remains a research center for multiple universities. You can only see Monkey Island (yes, some people call it Monkey Island) from a kayak off the shore, however, as Rhesus monkeys are carriers of Herpes B. Not so cute.
15. Christmas Island, Australia // Crabs
These bright red crabs can actually be a little eerie given their massive numbers. There are about 45 million of them on this teeny island, and they're actually a conservation success story. Once a year, millions of adult crabs march from inland forests to the shore so they can reproduce. It’s the beginning of an elaborate mating and spawning process that is triggered by the phases of the moon, and eventually results in the ground turning glittery red with baby crabs, each just a few millimeters across, marching back inland from the ocean.
The crab populations had been on the decline since the 1980s, when invasive yellow crazy ants (that's their actual name) began to swarm the island, and the baby crabs. But efforts to control the ant populations, and to protect the crabs from humans during migration with crab fencing and crab crossings, have helped the animals rebound. The 2015 migration was one of the best in 25 years. Good job crabs.