Assume that in Divinity there are places were you find a herd of animals. Now most animals have thier own reputation towards you.
Using the 5 point skill system in divnity...each time you invest in the skill you gain two benefits.
1) the animals attitude changes towards you for the better(passive skill) and
2) you can persuade one(then one more after each skill you get) such animal to follow you.(active skill)
Obviously you would "recruit" such animals from the above places..it doesnt follow from other games that a bear just happens to be summoned from anywhere.
Of course if you kill all members of a herd then you wont be able to recriut these particular creatures. The theory being that these animals are in a constant number.....becuase assume that some animals die and new ones are born. If you recriut all animals then again they will simply dissappear so be sure that at least 1 animal is there.
Of course if you happen to solve a quest which the npc has some animal then he may allow you to have an animal free of charge..that farmer imp guy in act 2 of <img src="/ubbthreads/images/graemlins/beyond.gif" alt="" />.
If you dont have this skill naturually these animals might attack you.
Being a druid its your skill to get better at taming more and more wild animals.