I live in a small city in the US, where it’s grass everywhere. There’s lots of rabbits, but why aren’t there more? They eat grass, and there’s clearly more grass than they can eat at their current population size. There’s no significant predators to speak of, I don’t think. They breed legendarily quickly, there’s even an expression about it. So if food isn’t a constraint, predators aren’t a constraint, what is the constraint? I would think they should just increase population until we don’t have to cut our grass anymore.
In: Biology
This actually reflects a really deep and interesting ecological question: to sum up, why is the world green?
Here’s a review paper on the topic which may not help much because i’m on ELI5 not askscience
[Full article: Why is the world green? The interactions of top–down and bottom–up processes in terrestrial vegetation ecology (tandfonline.com)](https://www.tandfonline.com/doi/full/10.1080/17550874.2016.1178353)
Anyway, to *heavily* sum up, it’s not immediately obvious why herbivores (all herbivores, not just rabbits) don’t increase until most green vegetation gets eaten not long after it grows. This is kind of how things work in the ocean, after all. Algae normally gets eaten as fast as it grows.
But there are several possible reasons, all of which probably play a role. First off, and perhaps most importantly, plants are not undefended. Plants contain all sorts of toxins and poisons and spines and indigestible matter than makes eating them time consuming and costly for herbivores. A field of grass may look all the same to you, but a rabbit is going to be focusing on certain plants and certain parts of leaves to maximize nutrition vs digestion effort. If there are too many rabbits, the food available won’t be as high quality. Second, predators and disease play a role. The more dense rabbits get, the more their predators and disease populations grow, which in turn limits the number of rabbits. Finally, herbivores can be limited by other environmental factors. So for example, rabbits want to dig burrows, but not all ground is equally suited for that.
Three years ago there was a serious rabbit issue in my neighborhood. They were everywhere. Then half way through the summer a fox moved in and solved our rabbit problem.
Rabbits are freakishly fragile. If they don’t eat for 24 hours, they die. If they eat something nasty, they can’t throw it up, so they die. If they literally get too frightened, they have a heart attack… and they die. Seriously, it happened to my friend’s rabbit… he was startled by her dog. Basically the only reason they still exist as a species is because they were mass domesticated about 1200 years ago to raise for meat, lol.
Now don’t get me wrong. I LOVE rabbits. I have had many rabbits and loved many more. But it’s a miracle that they’re still around lol
Everything eats rabbits, like everything that can consume meat is eating those little bastards. Pretty sure I even saw a video of a frickin seagull taking one down whole. Hell, I eat them when they wander in my back yard and I can get them with my bow or pellet gun. Free food at the wrong place and wrong time for them. Skin them, gut them, remove head and paws, pressure cooker with 4 Oz salsa and 4oz stock of any kind, 30ish minutes and shred. Rabbit tacos. Season to taste with lime and salt.
Everything eats them. Literally. We came back from a vacation last year to a large black snake nomming on a baby one, last year. Cats. Birds of prey. Raccoons, possums, heck, large rats. -Everything- eats them.
Man, by my house in suburban Chicago I swear the rabbits outnumber the squirrels this year.
Used to trap bobcats and sell the fur. It seems that when the rabbit population was higher then we would have a good trapping season. I assume when rabbit population gets high the predator population increases. Even in a city there are animals that will hunt for rabbits.
Here in the mountains we had a rabbit problem but after a few years they all died out due to inbreeding weakness and disease.
Manicured lawns don’t have enough protein in the grass to sustain them, so they only pick at flowers, gardens, and clovers. Many neighborhoods are very lean on these.
116 comments already but I just want to add, mowed lawn is not rabbit habitat. In the US it’s not native, and its a monoculture of one species so herbivores can’t get a diverse diet. But more importantly, short mowed grass is super exposed, for a prey animal that has predators on foot and in the sky. Natural grassland has grasses 1-3 feet tall. A rabbit on a lawn is a sitting duck
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