Viper (CR 1/2; XP 200)
N Tiny animal
Init +3; Senses low-light vision, scent; Perception +9
Defense
AC 16, touch 15, flat-footed 13
(+3 Dex, +1 natural, +2 size)
hp 3 (1d8–1)
Fort +1, Ref +5, Will +1
Offense
Speed 20 ft., climb 20 ft., swim 20 ft.
Melee bite +5 (1d2–2 plus poison)
Space 2-1/2 ft.; Reach 0 ft.
Statistics
Str 4, Dex 17, Con 8, Int 1, Wis 13, Cha 2
Base Atk +0; CMB +1; CMD 8 (can't be tripped)
Feats Weapon Finesse
Skills Climb +11, Perception +9, Stealth +15, Swim +11; Racial Modifiers +4 Perception, +4 [[[Stealth]]
Ecology
Environment any
Organization solitary
Treasure none
Special Abilities
Poison (Ex) Bite—injury; save Fort DC 9; frequency 1/round for 6 rounds; effect 1d2 Con; cure 1 save.

Vipers are not particularly aggressive snakes, but their poisonous bite can be deadly.