Animal Handling

Proficiency in this area enables a character to exercise a greater-than-normal degree of control over pack animals and beasts of burden. A successful proficiency check indicates that the character has succeeded in calming an excited or agitated animal; in contrast. a character without this proficiency has only a 20% chance of succeeding in the attempt.

Rangers

A ranger's Animal Empathy ability can produce essentially the same calming effect on an animal as the animal handling proficiency. If a ranger also has the animal handling proficiency, he may attempt to soothe an animal either by making a proficiency check or by using his animal empathy ability--but not both.

If an animal is among a ranger's followers, neither animal empathy nor the animal handling proficiency is necessary to control the follower. Use the guidelines in the Ranger's Followers article instead.

The animal handling proficiency has no effect on a ranger's species enemy.

Paladins

A paladin can soothe his bonded mount automatically; the animal handling proficiency isn't necessary. The proficiency may be used normally to calm other animals of the same species as the bonded mount, as well as other pack animals and beasts of burden.

[Player's Handbook]
[Complete Ranger's Handbook]
[Complete Paladin's Handbook]