n large animal swarm 

Perception +6; low-light vision, scent (imprecise) 30 feet

Skills Acrobatics +7, Stealth +7, Survival +4

Str -1 Dex +3 Con +2 Int -4 Wis +1 Cha +0

AC  16; Fort +5, Ref +8, Will +4

HP 16; Immunities precision, swarm mind; Weaknesses area damage 3, splash damage 3

Speed 25 feet, climb 15 feet

Nibble [>] Each enemy in the squirrel swarm's space takes 1d6 piercing damage (DC 15 basic Reflex save).

Scrabbling Swarm [>] The squirrels clamber over the creatures in their space. Each such creature must succeed at a DC 17 Reflex save or become clumsy 1 as long as it remains in the swarm's space.

Bestiary 3, page 257.