Since animals, unfortunately, can not wield standard equipment, here are two feats that resemble equipment found in the SRD. The first is meant for creatures with natural bony plates (like Ceratopsians and Brontops), and is meant to be a dumbed down version of a towershield. The other is more quick, low HD predators (like Velociraptor and Deinonychus, as well as Hyenas) to make them more of a danger in combat.
Unfortunately, they are a little powerful, so they need some PEACHing.
Protective Frill [Monstrous]
Creatures with protective bone coverings can make themselves harder to hit by positioning their body.
Prerequisites: Medium Size, Animal or Magical Beast type, has a protective bone structure (like a neck frill, antlers, or other head-based bone protrusions).
Benefit: By spending a move action to get into an optimum defensive position and taking no other actions afterwards during this turn, the animal is granted cover (+4 bonus to AC) until its next turn.
Special: Dire Animals (with the exception of the Dire Shark) have all sorts of bony spikes along their bodies, and automatically qualify even if none of the protrusions are head based or if it is smaller than medium.
Creatures with talons can use it to inflict heavy, and usually lethal, damage to enemies.
Prerequisites: Talon Attack, Animal or Magical Beast type, Strength 13
Benefit: Upon a successful critical hit with its talon attack, the creature may choose to tear the soft underbelly of its prey apart with a terrible slash if the prey is within one category of the creature and it has one HD less than it. Creatures without discernable anatomies (oozes, constructs –including living ones-, undead, and plants) are unaffected. The victim must make fortitude save (DC 10+ ½ creature’s HD+ creature’s strength modifier), or immediately fall to -1 hit points. A creature struck with such an attack cannot stabilize naturally. Mundane heal checks can stabilize a creature, but cannot save them from their dying state. Only magical healing can bring them back to positive hit points.
Special: Hyenas, despite not having talons, use this hunting technique. Hyenas, along with all animals and magical beasts related to them, can use their bite attack to fulfill the talon attack prerequisite when attempting to acquire this feat.