A couple of additional notes on mundane monsters.
The bite of an anaconda, big cat, or crocodilian causes serious damage (+ 1D6) on a roll equal to or less than half the number to hit; a viper's bite never causes more than than a single point of damage.
Each turn that an alligator or crocodile grapples a character, it may attempt to drag the character backward 2 m, usually into water, in lieu of its thrashing attack. This is an opposed Strength check. Because this usually takes place on muddy ground, the character suffers a - 1 penalty to the check, at the gamemaster's discretion. Characters dragged into the water while grappled suffers a - 2 in attempts to break the grapple and may drown, per the rules in High Seas.
Anacondas, big cats, and vipers are typically solitary; crocodilians maybe be encountered alone (1-3), in a small group numbering 1D6+1 animals (4-5), or in a large group of 1D6+6 animals (6 on 1D6).
Sizes here represent normal ranges - larger or smaller individuals may found, and should be scaled up or down in Strength and damage accordingly. For example, a caiman might be Strength 6 + 1D6 and do just 2 points of damage instead of four, whereas a beast such as Gustave could be have a Strength of 25, cause 6 points of damage with each bite, and resist three points of damage per strike with his thick hide.