Most abilities require a specific body part of one of the animals combined; for example, Horns is always found on an animal's head, and the combined creature will not have the ability if the correct body part is not used. Other abilities such as Herding are "inherent", meaning they can be passed on even if none of the herd animal's body parts are used.
Most abilities are used by the creature automatically, but some will only be activated on the player's command. These are called "triggered" abilities. They require endurance to be used and deplete it when they are activated. Abilities affect the electricity cost of a creature; having many of them and\or very powerful ones will make it more expensive.