This is because barring injury or disease they don't stop growing. As long as they have a food source they can keep getting bigger and bigger hunting larger and larger prey. Eventually humans become a target and let's face it many of us are pretty stupid when it comes to nature so we don't look out for things like the giant gator hunting us.
not just tigers but lions and tigers and bears oh my lol. but lions and leopards don't normally hunt humans it's mostly defense or wounded/injured and can't hunt its natural prey so they hunt the slow squishy humans instead. Polar bear on the other hand is the only bear that we are on his menu and he actively hunts us. wouldn't leave kids around some of the large snakes either.
Lions and bears will fuck us up if we front on their territory, but gators will ambush us the same as they would any other animal, and Tigers are the most cunning of the Big Cats, closest to the sabertooth monsters that our ancestors were terrified of. In Asia they have "Tiger widows", there are territories where the beautiful hunters will each bag at least one human.
Crocodiles actually are definitely one of the most notorious for hunting people. One of the most common parts of the problem is in a lot of rural communities in places such as Africa have livestock such as cattle. They take the cattle to the water, and the crocs, naturally, are attracted to them. Their goal is usually the cows (or goats or whatever), but at the end of the day they're hungry. If the thing they grab has 2 legs instead of 4 they're not like sharks where they might go "wait, this isn't what I ordered" and let go. Their immediate focus is drowning their prey and that's what they'll put their effort into.
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That said, it doesn't actually account for all croc killings. There have been several instances where they've discovered crocodiles that consider humans a food source and will actively hunt them. There was one very notorious croc that killed 30 people I think? (Don't quote me on that, I'm not sure the exact number). It was notorious and killed people every year
Snakes, by and large, also don't see humans as a food source. We're simply too big for the majority of them. That said, if a reticulated or Burmese python, or even a green anaconda, got hungry enough, the majority of them would probably not turn away from having a human as a meal. Generally they have to have limited options to other food source. Which is part of why the pythons in the everglades are such a huge problem - they get HUGE and they eat everything. And are currently running out of prey. Which isn't to say they're going to go on a people-killing spree, but they're already turning to alternative food sources, and if a child or such went wandering through it's not entirely unthinkable one might grab it.
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Polar bears I feel might have a similar plight where their food is becoming incredibly scarce, but I don't know enough about their attacks on humans.
Generally, though, the majority of these animals would prefer to avoid us and stick to what they know won't stab them with an exceptionally pointy stick
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That said, it doesn't actually account for all croc killings. There have been several instances where they've discovered crocodiles that consider humans a food source and will actively hunt them. There was one very notorious croc that killed 30 people I think? (Don't quote me on that, I'm not sure the exact number). It was notorious and killed people every year
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Polar bears I feel might have a similar plight where their food is becoming incredibly scarce, but I don't know enough about their attacks on humans.