Invisibility to Animals

Animals cannot perceive the warded creatures. They act as though the warded creatures are not there. Warded creatures could stand before the hungriest of lions and not be molested or even noticed.

(Player’s Handbook 3.0)
Originally posted on D&D tools

Abjuration
Level: Druid 1,
Components: S, DF,
Casting Time: 1 action
Range: Touch
Target: One creature touched/level
Duration: 10 minutes/level (D)
Saving Throw: None
Spell Resistance: Yes

If a warded character touches an animal or attacks any creature, even with a spell, the spell ends for all recipients.

Note: magical beasts and vermin are not “animals” as defined by the spell.