I've been putting this off for some years - but I am beginning to feel that the problem has to be addressed.
I do not like 'encounter tables.' I spent much time in the first two decades of my world-building attempting to create random tables for encounters, only to find again and again that the results on those tables did not make sense in the circumstances. It isn't enough to say that it's night in the jungle, there's a random encounter, let's see what it is. The particular circumstances matter. There are animals that do not emerge at night. There are places where the party might camp where the appearance of particular animals either don't make sense or where the existence of the animal offers no threat.
If, for instance, an animal is specified that guards it's lair very closely, it doesn't work as a wandering monster, does it? I would need to create some reason why the player is wandering, and not the monster, for the encounter to occur - and I don't like insisting that the player, on watch at three in the morning, wanders away from the camp to hear a sound. What if the rolled-up monster doesn't make noise? Or if the player refuses to wander away?
Most DMs would, I think, simply say, "Well, then there's no encounter, and the party wakes up and is fine." Which makes some sense - except that we should be reasoning that this is what happens every time an encounter isn't rolled! It's a jungle, nyet? In a jungle, there are always monsters just a stone's throw from the party, perpetually. To me, a 1 in 6 chance of encounter isn't the chance that there's a monster nearby that can be ignored - it means an encounter happens. To get that, it means every monster on the rolled upon table ought to be one that moves.
Which means a table for the jungle at night, as opposed to one in the daytime. It also means a different table for the party if they're camped near water, where they might get beasties showing up that wouldn't be in an upper valley. In fact, encounter tables begin to proliferate, if what I want is for them to be useful . . . and I have never had that kind of time.
Worse still, 'jungle' in my Earth-based world doesn't mean anything. Which jungle? The Amazon? The Congo? Orissa, Mexico, the Mekong basin or north Queensland? Because the same animals don't appear in all those places - far from it!
Nor can we say that well, at least the monsters are universal - because they're not. A couatl is clearly based upon Olmec or Toltec roots, while the huge cow-like body of a catoblepas makes no sense in the watery Amazon. The Amazon might logically be full of slaad and other giant frogs, but what would these things be doing in the mountain jungles of New Guinea or New Zealand? 'Jungles' are not all alike - they do not have the same vegetation, the same topography or even the same climate. It rains practically every day in Panama, the year round, while the Northern Territories experience staggering dry periods - yet both are considered 'jungles.'
To make good lists, then, I'm facing a considerable uphill effort - made worse by the fact that less than a hundred or so possible jungle 'monsters' split into various tables gets pretty thin. Which tends to make more universal monsters like spiders and centipedes occur again and again, until the party is spectacularly sick of them.
I'm not happy with a make-shift list of 8 monsters, nor do I understand why anyone is. That works if the party wants to go to a jungle once for one adventure, then to go elsewhere. What if the party decides to stay? What if they remain through twenty or thirty sessions, because they're interested in what they can make the jungle do for them? What are they going to do, fight giant centipedes and wolf spiders night after night?
Problems like this are the reason why I've given up on encounter tables - but running sessions lately, I'm beginning to realize more thought is needed. I had one such encounter happen recently, with a jaguar, for which I was able to use some researched notes on the way jaguars attack that I had written four or years ago. And it worked brilliantly. I was so pleased I had those notes. They were similar to the ones I included in this post.
Now, I realize I have to make more of those - no matter how much work that means. But whew - and I looking at one big mountain to climb!