> But deer are pretty?!

Deer are simply tall, disease-carrying vermin--basically rats with long legs.

They eat everything. They multiply like bloody rabbits. They host a ton of diseases--especially when overpopulated (effectively everywhere that doesn't have lots of wolves or big cats).

I really don't understand why we don't hunt them aggressively when there is no apex carnivore to keep them under control.

Adult humans are often infected with various forms of the Bambi-Rudolph disease complex. Usually acquired in childhood, and very difficult to cure.

Invasive species in Australia, but it was introduced to hunt.

And hunters aren't sadly dumb enough to wipe the species out. They whittle down their numbers, and then leave them alone to repopulate.

Leading to my shock when I wrote off my car by hitting a deer, instead of a kangaroo as god intended.

Hmm. I live among deer. They're fairly pleasant creatures and interact with other species such as magpies and house cats. We do have pumas and a few human hunters, and high speed motor vehicles, possibly the odd wolf here and there although I've never see one. Over 25 years I haven't noticed an increase in their population.

Oh yeah, but I'm talking about the UK. All the big predators, cats, wolves, have been eradicated. Hell, even bears and boars.

It's this bad.

Indeed. For the UK in particular you clearly can't have "What it was without people" because that's far too long ago, there aren't records so we'd only be guessing. The New Forest - near me - was built about a thousand years ago, it's not "supposed" to be like that, it was built on purpose and it takes considerable maintenance to keep it that way, felling trees, managing trails, maintaining bridges and so on. Things like "The pigs eat acorns, that way the ponies don't eat the acorns and die†" could not possibly work without humans managing the forest. Left to their own devices the pigs would destroy that forest in a few years, and then the ponies die too, humans allow pigs out for a set period, to eat lots of acorns, then bring them all back by law.

We could try to build what was there before the forest, but it would be extremely disruptive to all the people who live there, and what for? The Forest isn't very useful today, but it's pretty and we know it's stable, and it has some uses, we grow some trees there, we farm some pigs and ponies, tourists come to see it - there are many worse options.

† Acorns are poisonous. Don't eat acorns without proper preparation. Unless you're a pig or a squirrel or something. In which case how are you reading this note?

Something I learned recently, acrons (properly prepared, they are indeed poisonous otherwise) used to be a human staple food in the Americas. It was displaced because it is annoying to prepare and the taste is relatively bland.

When I was a kid my family spent a day on a Native American Culture experience at Yosemite National Park. It was really cool! Flint knapping, and brain-tanning, and basket-making, and beadwork, and dancing, all led local tribe-members. Pitched at tourists, of course, but real content, and genuinely interesting.

Anyway, one of the deals was pounding and preparing acorns with a group of the older ladies. We went through the whole process, including cooking the mush with hot stones in a basket. It was... terrible. Bland, with astringent, tannic overtones. I remember my mother (not the most culturally-sensitive of people) asking incredulously if they really eat this. The woman who'd done it with us laughed, and said "No!", but that her grandmother always had, and for the kids (her), she'd always added lots of butter and brown sugar!

Sidenote: that woman was probably seventy, in ~1985, so her grandmother must have seen some shit. I wish I'd been old enough, and educated enough, to have appreciated that at the time.