Dire Bat (CR 2)

Large Animal
Alignment: Always neutral
Initiative: +6 (Dex); Senses: blindsense 40 ft., Listen +11*, and Spot +8*

AC: 20 (-1 size, +6 Dex, +5 natural), touch 15, flat-footed 14
Hit Dice: 4d8+12 (30 hp)
Fort +7, Ref +10, Will +6
Speed: 20 ft., fly 40 ft. (good)
Space: 10 ft./5 ft.
Base Attack +3; Grapple +10
Attack: Bite +5 melee
Full Attack: Bite +5 melee
Damage: Bite 1d8+4
Special Attacks/Actions: -
Abilities: Str 17, Dex 22, Con 17, Int 2, Wis 14, Cha 6
Special Qualities:
Feats: Alertness; Stealthy
Skills: Hide +4, Listen +11*, Move Silently +11, and Spot +8*
Advancement: 5-12 HD (Huge)
Climate/Terrain: Temperate desert
Organization: Solitary or colony (5-8)
Treasure/Possessions: none

Source: Monster Manual

Blindsight: Dire bats can "see" by emitting high-frequency sounds, inaudible to most other creatures, that allow them to locate objects and creatures within 120 feet. A silence spell negates this ability and forces the bat to rely on its weak vision, which a maximum range of 10 feet.

Skills: Dire bats receive a +4 racial bonus to Spot and Listen checks. These bonuses are lost if blindsight is negated.

Dire bats swoop down upon unsuspecting prey from above.