Adventures in the Canopy (System Neutral)

Known as the mega forests of  Cul Tur in my game world. Just East of the second dwarven  stronghold, nestled between the  mountains and the coast. Once home to loosely united Rakasta tribes, now just shadowy jungles left unexplored. No one has ever gone there in game, I doubt anyone will.

I guess it's safe to blog about my thoughts on one of the least talked about biomes in fantasy RPG's.

Lets Jungle....

The Forest Canopy:
When it comes to  real life biodiversity  the Jungle canopies are some of the most biodiverse places on earth. Keeping this in mind, it's easy to extrapolate that in a magical fantasy setting the canopy perched high above the floor of a jungle could be home to just about anything.

Native vs Non-Naitve:
One recurring theme in this blog will be that of native Jungle dwellers Vs visiting  travelers. The Native populations will have EVERY ADVANTAGE in this territory with the possible exception of technology. Most native societies in jungle terrain subsist via hunting and gathering. Everything they need the jungle provides. The technologies that helps other societies produce more things with fewer resources are just not necessary.
It would be easy for a party to think native people are somehow not as intelligent or capable as they are. That would be a fatal mistake.  The  Native populations in jungles are masters of their environment, they have to be. As such they do not suffer most if any of the penalties listed in this document. They hear better in the jungle, move faster, and see farther than visitors. They know what to eat and how. They know what's poison and what's not. A native population will use all of these advantages to help or hinder a party based on how the party interacts with them. It would be wise for a party to  approach the people living in the jungle with respect and  as possible allies. Anything else should be taken by the GM as a good reason to make the characters time in the jungle that much more difficult.

Native weapons:
Like I said the forest provides. Natives will used the  things they have learned living in the forest to their advantage when crafting weapons.

• Blow guns are fast to aim and when treated with  poison from native creatures (famously poison dart frogs) lethal.  An effective range of 30 to 40 yards is a good place to start if you game does not have rules for blowguns.
• Spears: Used to spear fish, sometimes poisoned for monkey hunting, rarely thrown.
• Short Bows: Some tribes use very  compact bows made from wood, vines, and hide. These small bows are perfect for maneuvering in the clutter of a rain forest and in the hands of an expert are not hindered by the foliage in any way.   These bows can be treated as normal short bows for game purposes. Arrows are often light and poisoned.
• Cudgels knives and clubs. Most simple weapons are well within the  capabilities of Jungle native, usually created from wood, or other natural materials. Some are ceremonial while some are reserved for wars with other tribes. Often good fighting weapons are not great hunting weapons.
• Armor: Natives in a rainforest will rarely wear armor. Instead relying on their deep knowledge of the  terrain, surprise and mobility to protect them.
• The use of poison is part of  jungle hunting culture. An art passed down  through generations. The climate of the jungle makes lighter ranged weapons advantageous Poison is a part of hunting  that ensures game kills by compensating for lighter ammunition. There is no morality about using poison in the jungle. Poison is how food is attained while expending the least amount of resources. Native warriors will not have any inclination to not use poison on an aggressor. Players beware.

Weather:
Just some quick hitters here: The average temperature of a rain forest is about 77° Fahrenheit but can
range up to 100 degrees during the day and drop back down to 50 Degrees at night. The annual precipitation of a rain forest is greater than 50 to 260 inches per year. During the rainy season as much as 4 inches can fall in a day of steady  unrelenting rain. Furthermore even more precipitation comes from the forest's own evaporation. The heat, daily rain, and condensation makes the rain-forest extremely wet and oppressively humid.

What does this mean for a party of adventurers? Trying to traverse this terrain in full armor of any beyond studded leather is pretty much suicidal. Metal items such as weapons and armor will suffer and need to be meticulously maintained. Chain mail and plate mail will stiffen quickly, within days of entering a rain forest. Blades will dull, over time even leather will begin to rot right off a character.
Armor and weapons can be protected vial oiling to keep away the moisture. This will have to be done daily.  Magical means of preservation are also a good choice if your game allows for it.
Magical weapons and armor should be allowed more time before any degradation occurs. If the DM wants to have the climate effect enchanted weapons I think saves vs the elements that get progressively more difficult as time goes on are a good way to go. Nature will have it's way even with enchanted items if given enough time.

Storms when they strike can be sudden and violent. Lighting strikes and falling limbs make it very wise for characters to find shelter as soon as they can.
If the GM determines a severe storm blows in. Any characters caught in the trees or outside on the forest floor must check each turn  to see if they are hit or at least threatened by blowing or falling debris. As a reminder heavy branches will and do fall, and from great heights. I feel these checks should  be cumulative, meaning the longer the character is exposed the better a chance something will fall on them.

Use the chart below to determine things that befall the characters when left exposed to a bad storm.

• 1- 25 Loose debris, the character must spend a round dealing with getting the wind blow debris off of them.
• 26 - 50 Small branch, the character must make a low difficulty check to keep their footing. 
• 51 -65 Branch, the character gets whacked by a falling or blowing branch taking light damage.
• 66 -73 Bigger branch: The character gets hit doing moderate damage and  losing their footing. there is a 15% chance the branch pins the character.
• 74 -84 Vine fall: A group of vines have fallen on the character or party, they are effectively entangled. the  group might sustained light damage , if the  vines or  from high enough up.
• 85-93 large branch: This falls at the character, give them a roll to avoid it for half damage otherwise they should take heavy damage, have a 40% chance to be pinned.
• 94 - 97 Tree fall: A large tree uproots and falls. Hopefully not the one you are standing in. This is a big deal basically encompassing the whole chart in one roll. All hell breaks loose. Characters should save for half damage or  take a huge hit. Characters will be caught up and entangled 90% o f the time by the  mass of branches and vines that come down with the tree.
• 98-100 Lightning strike: Lightning strikes a tree near the characters. They take electrical damage based on the system being used. There is a 10% chance a fire starts on the ground among the forest floor litter.

Small rain storms, and even longer soaking rains happen daily in a rain forest. Not every storm has to be violent. The Gm should mention rain at least once a day to remind player exactly how wet and oppressively humid their surroundings are.


Visibility and Senses:
Leaves, massive tree trunks, branches, vines, all make it easier to hide. Furthermore there is a lot of background noise in a jungle setting. Checks to perceive threats are far more difficult for non native characters. Once above the ground in the canopy a character is lucky to see beyond their own tree and into the next 30 to  50 foot visibility at best. If the characters go higher to get above the canopy they will only see a sea of green below them stretching for miles. Good to see a tower or massive tree the party is looking for but not so good for finding that monkey that just stole their scroll case.

Range:
Ranged attacks again for non native shooters, should be heavily modified to account for the clutter of limbs and leaves the  character is trying to shoot through.
A smart party might offset some of these problems by gaining a height advantage on an opponent. There are ample opportunities to go upward when the  situation calls for it. Shooting down on your target will offset some of the negative modifiers.

Travel:
 The ground level  will be surprisingly devoid of apparent food, dark, punishingly humid and eerily quiet. For the  most part the  massive trees catch 90% of the sun, most of the rain, and keep the forest floor covered in a constant litter of  sound dampening leaves. The thick undergrowth of vines and stalk plants make ground travel difficult and slow.
Traveling on the forest floor at least keeps the party safe from falling out of a tree but it's best to  bring plenty of rations you can trust, or at least a knowledgeable guide.

• A ranger Could make a moderately difficult check to know that this kind of forest will not offer good good chances to hunt large game. A guide or ranger can keep you alive via forage.
• Foraging is at a disadvantage and or a high difficulty for those attempting it. Things are strange here, there are many dangerous plants and animals not found anywhere else.
• Any fruit or plant eaten will have a chance to be poisonous. In the jungle everything gets eaten by something. Plants and animals have evolved unique, varied, and surprising natural defenses. In short everything is trying to kill you before you have the chance to eat it.
• A knowledge check by a ranger or Druid can locate small sources of potable freshwater. Pitcher plants, wet moss, the undersides of large leaves, hollow stalks and some wet root balls are all options for fresh water. This check is to find safe fresh water, not just any old water.
• Larger sources of water such as pools and streams, even rivers are also plentiful, and obvious. These also draw other animals, and are known by locals.  
• Party members would be wise to  be wary of  water in the open, as it is likely to carry parasites. In this environment stick to boiling everything. ("purify food and water" can save a D&D style party!)
• Making headway will be slow as the group will often have to chop their way through the underbrush. If characters are using their normal weapons to do this the GM should apply penalties to any character who does not  take time to maintain their weapons at the end of a day. (this compounds the damage the wet environment will do.)
• A Druids magical abilities would be very useful in this environment.

Strenuous work, such as combat, hauling heavy loads, and even just walking if armored can cause great fatigue in the humid and wet conditions.

(One version of D&D lists Fatigue as: A fatigued character can neither run nor charge and takes a "-2 penalty to Strength and Dexterity. Doing anything that would normally cause fatigue causes the fatigued character to become exhausted"
and Exhausted as:
"An exhausted character moves at half speed and takes a –6 penalty to Strength and Dexterity. After 1 hour of complete rest, an exhausted character becomes fatigued.")
I don't think this way of handling things is all that bad.

 After every hour of  working in the  heat and humidity of the jungle have players make a check for their character with penalties applied for medium or heavy armor. If the check fails the character becomes fatigued. On the next check a fatigued player becomes exhausted, and if an exhausted character fails the check the character passes out cold.
Resting for an hour will bring a character from exhausted to fatigued and a fatigue character back to  normal.

If on a march in normal terrain the characters could cover 25 miles along a good road on a good day. In the  rain forest the same party might (Might) make 12 miles in the same day.  Bushwhacking is hard work and the  characters will have to take frequent rests. (see above)
Unless there are trails cut for the party horses are useless, mules are better but not by much.
considering we are talking about fantasy games there may be some magical native species that can act as beasts of burden. Examples might be giant lizards which can climb the trees, large bats, or whatever the GM can dream up.

Moving in the trees is another matter.
I wrote a post about falling a while back:

Things get more interesting in the  canopy high above the forest floor. The understory layer up through the canopy are worlds of damp  mists, foliage and predation. 

The  continuous layer of  dense foliage formed by adjacent tree tops is known as the canopy. This area  starts around 100 ft up and runs as high as 150 ft or for our uses 200 ft into the air. What makes the  canopy  interesting  for  adventuring parties is the overwhelming biodiversity of the place. Animals and plants adapted to living in the trees and nowhere else make the canopy a treasure trove of rare spell components and medicinal resources. 

Travel in the canopy is  dangerous. First things first, the characters are high above the ground. Add to that the unsteadiness of branches, the  inability to see, and an ever changing surface underfoot, falling becomes a very real threat.

Moving within a tree is one thing. If a character climbs a tree and is reasonably careful while in the tree a game master may not need to ask for any checks. For example a character who  ropes off once he or she is in the trees and  states that they are taking  care when moving about should get the benefit of the doubt from the GM. The player who says "I'm gonna climb the tree and grab the orange fruit," without any expressed thought about safety should be asked to make checks.
Moving from tree to tree should always require checks. Running, jumping, or otherwise moving with haste or recklessness should be rewarded with harder checks.

When a Character is moving through  the canopy tree to tree.

• Make a Check to see if the characters moved from  tree to tree successfully, apply modifiers for care  or  recklessness shown by the  character.
• Passed: Good! The character has jumped to the next tree!. 
• Failed:  Opps.. Roll 1d10.
• 1-5 the character stumbles and falls to the next tree taking a small amount of damage. If the player chooses to continue moving without taking a moment (round turn however your game measures time) to gather themselves then they will take a negative penalty on their next movement roll. These negative penalties are cumulative each time a player fails a roll and decides the character should keep moving. The penalties are reset if the character does nothing but gather themselves for one round or turn.
• 5-8 Minor fall: The character falls and lands on a lower branch! He or she takes moderate damage. and receives a penalty to any further movement unless the character stops to gather themselves.
• 9-10 Full fall!: The character plummets to the forest floor taking full falling damage. This stops movement and just may stop any other biological functions the  character might have been trying to maintain.

Using D&D as an example Spells like   "Freedom of Movement", "Long Strider", "Find the Path", Transport Via Plants", and  definitely the druids "Tree Stride" are very valuable in this terrain. (Or whatever the equivalent spells would be in your system of choice)

Climbing:
Using a small rope and a crossbow to fire a small leed line into a tree, then using that leed line to pull up the parties studier climbing ropes is one of the best non-magical methods for getting ropes in trees. However it's not as easy as it sounds, the shot will be difficult and the character might need to make a few attempts before success.  Once the characters have a rope getting into the trees is a matter of brute strength. Most games represent a period before harnesses and  ratcheted foot ascenders climbing gear. Characters will be  pulling themselves up a rope and slipping it around their feet for support, not easy. If they are lucky the characters might know how to make a Prusik knot to assist in the climb (perhaps a ranger? or a survival skill check  depending on your system.)
Climbing could be a series of tests up to one per 10 feet as decided by the GM considering  situation and conditions.  With each failed check having a worse result for the character. A bit like the  D&D5th-Ed Death saves. 

• First check failed the  character is tired, and slows down. 
• Second failed check the character starts to slip back, losing grip and stability.
• Third failed check the character falls from whatever height they had achieved.

The first two failures are an invitation to slow down and rest. A character could grab a limb and sit, put a spike in the tree and stand or otherwise figure a way to rest. resting  resets the failed checks, but also invites the GM to roll on a random encounter chart, or have the bad guys catch up. Time is a resource after all.
Hastily made harnesses and ropes tied off to limbs will mitigate falling damage. Though  falling, crashing through tree limbs and swinging like a screaming pendulum into a  nine foot thick tree trunk should not be without it's consequences.

Not to sound like a broken record but all this climbing business is old hat to the natives living in the jungle. They  will be just plain better at it even if a character hits their skill checks and has some form of training (Athletics, Acrobatics, so on.)
Medium or heavy armors are major hindrance when climbing. The extra weight is just not desirable when hoisting ones self into the air. A GM could ask for more checks from armored climbers or make their checks more difficult.

Free Climbing is the act of climbing  a tall tree without the  benefit of ropes. This works the same as rope climbing only the character does not get a chance to rest unless they find a feature in the tree which can support their weight. Free climbing is very dangerous and over armored or over encumbered characters shouldn't even think of trying it.

Rappelling is no easier:
Rappelling should work very much like climbing only  a characters dexterity or equivalent should be used rather than strength. A character can  mitigate some of the  risk by preparing to rappel properly.
If the player takes the time to  declare his or her character is finding a good tree to rope off to and can make a skill roll to set up an effective rappelling system. A ranger or guide would know how to set up for rappelling and  have a fair shot at doing it correctly.  If a character tries to set up a rappelling rig very quickly or thoughtlessly the GM can  give them negative modifiers to the characters checks on the way down.

Failed rappelling rolls Roll below 1d6

1. Item of clothing stuck in the rig, the character is stuck swinging in the breeze some  distance from the ground. Make a check to repair.
2. Rope slips! character drops  a bit but is otherwise OK. IF the character gets this result again re-roll.
3. Frayed rope! The rope is starting to fray here ever it is tied off. If this is rolled a second time roll again.
4. Rope snagged: All progress halts, the rope will need to be cleared. Make a check to repair.
5. Rope breaks! the character falls unless they are roped off or have figured out another safety method.
6. Rope really slips! Character falls quite a ways and the rig gets tangled. Character on the rig is stuck the rig is to far gone to repair from mid rappel.

Bridges and structures:
Native peoples may have built structures in the canopy. Bridges, rope swings, zip lines are all possibilities.

These structures are difficult to build, dangerous to maintain and take up a great deal of time that a jungle dwelling  person might  better spend gathering food, or hunting. As such these structures are never over built.

A well equipped party traipsing over a wicker bridge may make a GM want to  roll checks for the  integrity of the structure.

Thief and rogue types can  go ahead of a party checking the structure. Use normal find traps protocols for a  Thief looking for structurally weak areas. If the  party has a dwarf that is skilled in building, more the better.
Breaks in canopy bridge should have some fore warning. Cracking noise, shaking of the structure, and planks plummeting to the ground. Those kind of tips might let a wise party know to  slow down or to travel one at a time.
Naturally when a party is taking it safe and are strung out one at a time over a long bridge 200 feet in the air, that's the perfect time to attack them.


Fighting in the canopy:

Source

Each game system is going to apply its own penalties for  fighting in strange environments. For fighting high in the canopy I would use your systems  penalties for unsteady footing, and limited vision just to start. Keep in mind that  any creature or person native to the  rainforest is going to understand verticality, and take advantage of higher ground whenever possible. Imagine if you will a paladin cowering under her shield as enraged apes rain coconuts down on her form 150 feet up.



Ranged weapons while limited due to cover, can be superior in a canopy fight due to the difficulties involved in closing with and engaging  enemies physically. Again, native creatures will be able to disengage and retreat more effectively than non native warriors will be able to advance through the  canopy. Wise players will try to force or lure enemies to the  ground where the  fight is more on the  characters terms. This may or may not be easy to do, as rappelling from trees is as dangerous as climbing them.

Disease: 
The mosquitoes are inescapable, and some fo them carry disease.
While I think it would be harsh to give a player character Malaria, I do think it could make a nice story hook to have to find a cure for some NPC's horrid case of Dengue fever.
It would be fair to make a character make a check once every three days to avoid a tropical fever or a mild disentairy. I am not suggesting that Fair Fillred the Paladin should shit himself to death in some god forsaken jungle, that's a terrible way to loose a character.
What I will suggest is that any  character who fails the check should pick up the  "Fatigued" state until they are cured or can rest for  three days. Making them fatigued will make them get exhausted quicker, and will generally be  a pain in the player's ass.
I also suggest that for every player that gets ill due to a failed check , an NPC or retainer should get severely ill, or even die. Just so the player realize disease is serious business.

Another consideration for any character wearing boots, or god forbid armor all the time is "Trench foot" or Immersion foot. Caused by wet foot conditions and bad hygiene, this little marvel can cause gangrene and  loss of a foot if let go.

I would  say that when the  players have a rest and  start a camp fire the GM  should ask if they are  taking off boots and Armour. If they constantly say no, then each day they have 10% +2 percent chance of developing Immersion foot and or a horrid fungal infection of the feet. This will half their daily movement, and if let go will start to drain "Health" at a slow rate each day. (based on your  chosen game)
The Idea here is that players should be aware of their environment and after a few hints be willing to shed armor and dry off tier covered parts. It's not to punish the players but to drive home that the jungle is not  their normal stomping grounds. Helpful natives will offer sandals, or even directly tell the characters of the danger of never taking off their clothing in the jungle.
Again magical healing and good guides will help tremendously.


As always  If your game of choice has good rules for disease, use them.

Opportunities:
One major reason a party might enter a rain forest is gather and locate materials for spells and potions. The  Rain forests have been called earths pharmacy  for their diversity of mostly undiscovered medicinal plants. A wizard or apothecary might pay premium rates for  plants gathered from such a hostile locale. For example the Cinchona Tree is used to make quinine, a cure for malaria, treating stomach problems, stimulating the appetite as well as treating blood disorders, leg cramps, and varicose veins. This is just one such example out of Thousands of real life examples. As a Gm build off what's real and extrapolate it.
The oils of the  Annatto Tree can be used to make a natural sunscreen, but in the hands of  Blodot the wizard it can be used to make a potion which renders an individual invisible while in the sunlight, and incorporeal in the moonlight.

Simple exploration: The party is hired to explore this new land "discovered" by a local sovereign. An expedition must be organized and executed.

Finding the explorers: Remember that expedition from before... Well they never came back.. so go track them down.

Lost city found: Anything can remain hidden for a long time in the jungle, a lost city has been found and your group thinks it is a great idea to  try to gt to it before any one else. Unfortunately there is a rival group of explorers with the same idea!

Encounter ideas:
I don't  use "giant" insects all that often in my game however, the hot humid oxygen rich environment of the canopy is exactly where I would start dropping them, and in  great numbers. The canopy being one of the very few in game areas I think would provide both the food and conditions suitable for large insects colonies.

Some  Plants and insects have developed symbiotic relationships, where as a species of  beetle or bee is the only species that pollinates a particular tree, or distributes a tree's seeds. In return the insect benefits from the tree as a source of shelter, protection, or nourishment.
Play this up as a GM.
For example:

• There are large thousand year old, 70–80 meter tall emergent trees that tower over even the  general canopy. Some specimens are as big around as a small house with  circumferences topping 90 feet. These trees have an upper canopy  made of  thick broad leaves.
• These trees are a form of beech nut tree. The seeds of these trees is prised by apothecaries, native people, and magicians as a medicine and a spell component. 
• Unfortunately the seeds are locked away in large highly poisonous fruit high in the trees upper branches. Eating the fruit can be deadly, causing  pain, blistering, swelling of the esophagus and eventual asphyxiation. Just don't.
• The  primary transporter of these seeds are giant leafcutting beetles. 
• These insects can be as as large as a goat. The maintain nests made of cut leaves high in the  trees foliage. The insects feed on the highly poisonous fruit pulp of the trees and leave behind the hard seeds. 
• The fruit of the tree is poisonous, and because it's the only thing the insects eat they have in turn become poisonous. their mandibles can inflict a poison bite that is difficult to resist and causes blistering and discomfort along with some damage..

Having a 60 foot around 45 meter tall tree tip over is another good use of the large canopy producing trees. Such a tree could be hollowed out by any manner of creature. Used as a shelter by native humans, carved out by giant termites, home to  a large trap door spider, or a colony of smaller dangerous insects. One thing is for certain in the damp gloomy forest floor region even a large stump would be temporary given the variety of fungi and molds that can develop. No matter what the size of the tree it would rot and be reclaimed by the forest relatively quickly.

• A very large tree has fallen opening up a small swath of the forest to sunlight. 
• The  downed tree is now covered in a veritable botanical garden of  hollow grasses, vines, flowering plants, and young trees taking advantage of the available sunlight. If you didn't know what the  fallen tree was you might miss it all together.
• Inside the stump and the remains of the tree termites and burrowing beetles have been hard at work hollowing out the vast fallen tree.
• The interior of the tree is now a series of hollow chambers. 
• These chambers have become home to  several  budding green slimes.
• The locals have cut a hole into the  hollow stump and covered its gaping roof with animal hides. They have used fire to harden the interior of the stump and are excavating the  dead trees vast root system. They are looking for a rare fungal deposits which are used by their shaman to make a hallucinogenic ritual beverage. The roots and the digging have formed a complex multi level cavern.

Predation:
The  Understory or layer of  foliage from the ground up to the canopy proper is home to a myriad of predators. Not least of which are the great cats. Large cats in a heavily wooded area create their own set of issues for a party.

• The great cats are stealthy, ambush predators who use the short lines of sight lines the jungle to their advantage.
• In a fantasy game the great cats will go for surprise every time.
• Ocelots: Small fast hunters, not likely to attack a human, but  perhaps. An Ocelot might  hit a small character (half-ling, Gnome, Elf) then take off, being able to easily outpace most characters.
• Panther: Medium sized, Hunts in the trees. Think about that, IN THE TREES. The characters think they are all safe camping up in the  tree limbs.. guess what.... Panther.
• Tigers: Huge, Nocturnal hunters , almost silent when they stalk prey, can easily kill a man. 
• Jaguars: The Swiss army knife cat, stealthy, fast and  powerful. Attacks first with a massive bite aimed for it's preys neck. Deadly if a character does not see it coming.
• As a GM I would give a great cats the equivalent of your games snake attack bonus on their first strike.
• The pelts and sometimes the teeth of great cats can often fetch a party high prices outside of the jungle.
• Some tribes may worship great cats, perhaps even one exceptionally large and strong individual cat.
• Dire versions of  great cats and Saber toothed cats are listed in many games standard monster lists.

Monkeys and Apes:
I made a random monkey generator a while ago.
The  Disoriented Ranger wrote about Apes and a module called Monkey Business not log ago.
Apes and Monkeys move about the canopy with a grace and speed that would make any adventurer jealous if it weren't so scary. Apes and monkeys are naturally smart, add to that the  trappings of a fantasy  game and the  characters could have their most fearsome opposition.

• Apes will always have advantage in combat while in the trees. They can hang upside down, run up trees, throw things, and jump great distances. Fighting a pack of monkeys in the  canopy is a bad decision for the party.
• Gibbons: Small fast, travel in packs. They steal stuff and run away.  Mostly harmless unless fought in a pack. In this case use your games swarm rules.
• Chimpanzees; Strong and agile. They use advanced pack tactics to confuse and isolate characters. Individuals will flank and go for sneak attacks. They are smart enough to target the face , eyes and throats of  characters. Each individual can get multiple attacks per round. Will eat meat.... Will eat characters.
• Gorillas: Usually peaceful gentile giants, They live in troops of females generally lead by one

  

  NOPE

  large male. Sometimes younger males will be present in the troop. Troop leaders will defend their territory. Massively strong, they will throw heavy objects, Charge, grapple, swing limbs, had out massive bites with their huge canine teeth and  basically wreak house. They don't attack in and organized way, but their individual bulk and power make them deadly even to mid or high level characters. 
• Give Gorilla's Fighter or warrior levels. 
• Unlike monkeys, Gorillas tend to build nests on the ground.
• Orangutan: the most solitary of the great apes. These long armed apes are more likely to run from adventures than anything else. These can be the wise old men of the forests. If I were going to  create a hedge wizard ape it would be an Orangutan.
• There are hundreds of small monkey species, most are just an omni-present nuisance in the jungle.
• Dire, Giant, and primitive variations of apes are possible. Extra intelligent Apes are a great idea.

The preceding blog post represents just the tip of the ice-burg for jungle adventures.

Giant spiders, Cayman, Naga, lizard-men in the rivers, Troglodytes in massive moss caves, Giant snakes, and so many other  creatures could make an appearance.

Though for my money it is the terrain and the environment that provides the greatest challenge. How will your adventures navigate such a foreign dangerous place?

Thank  you for reading...

-Mark

Here's some stuff I looked at while prepare this piece. There are more ideas lurking there than I used.

Pathfiner info
Medicinal Plants
Climbing the  tallest trees.
Account sort of our history is not grand folks.
Rappeling
Biome info, and here
Six things to know before you hit the rainforest.
disease info
Tropical disease
Blowgun arguments
D&D wiki
cats Run the internet.