Which mammal does not have gallbladder?

There are some animals that have evolved to not have a gallbladder - the horse is probably the most commonly encountered of these animals. The horse doesn't need a gallbladder - the function of the gallbladder is to store up bile between meals for digestion after the consumption of a meal. As horses have evolved to graze and eat almost constantly throughout the day, they don't have "meals" for the gallbladder to store up bile between and they evolved to not havea gallbladder.