From what I've read, feral cats are a bigger problem than domestic cats in the US. That's not necessarily the case on islands or other areas where cats aren't native. Especially where we're trying to reintroduce endangered species. They don't have the population to withstand a predator like the cat who hunts not just for food, but for the experience. Not that cats are the only four legged predator that hunts "for the thrill."
Female cats reach puberty between 5 and 9 months, although, some mature as young as 3-1/2 months. Once they reach puberty, they are able to reproduce. Outdoor cats, or those around mature, unneutered male cats tend to mature even sooner. A female cat goes into heat every two to three weeks, unless impregnated. In which case, the pregnancy is about 65 days, and once she's given birth, she's back in heat ... even while nursing. Consequently, a cat can have litters two to three times a year, with each litter having one to eight kittens. Unlike humans, cats don't go through menopause, but will keep on getting pregnant until they die. Fortunately ... feral cats don't live as long as indoor cats. But still ... that's a lot of cats. Males don't have the downtime of pregnancy, so the only thing stopping them is the lack of female cats in heat. Or exhaustion ...
Still, with all the damage humans are doing to the environment and wildlife habitats, there just isn't any good reason to let our well (over) fed house kitties outdoors unsupervised. I don't believe Taeyn, Tsuki, or even Sushi were harmed by keeping them indoors. While Tsuki is at the door when I get home in the evening and shoves out the door as soon as it opens enough, she now rarely bolts down the hallway. It seems to be more curiosity than I NEED OUT! Most of the time, she stretches out along the stairwell door (We're at the end of the hallway).
Even when she did bolt down the hallway, she never got all the way to the end of the hallway. Though, I'm absolutely sure that if my door opened to the outside, she'd probably take off exploring. A hallway ... while full of interesting smells ... just isn't the same as the fascinating outdoors with all those birds and squirrels.
If I didn't live in an apartment, I'd have a
cat run/enclosure on a deck. Big enough for a comfy chair for me too. Actually, I'd love to put one on the balcony here.