In Age of Empires II, sheep are a common food source that is beneficial in the early stages of a developing game. Nearing a neutral Sheep will cause it to become aligned with the player's faction. As long as units are within close proximity of the Sheep, they will remain under the control of the player that first discovers it (except if Celt units come close). If, however, no friendly units are nearby and another team's unit happens to pass by, the Sheep will fall under the control of that said player.
Sheep are extremely useful in the early game to maintain food (and hence Villager) production, as rapid development of farmland may simply not be feasible due to a lack of necessary resources, which is an issue in the Dark Age. As the game progresses the need for Sheep gradually decreases as Farms become plentiful and effective in the later stages of the game.
Sheep can also be used for scouting, but have a very limited Line of Sight of 3 and speed of 0.7. Despite there being a risk of losing them, in island maps or maps where players start without a scout it can be relatively safe.
The Celts have the unique advantage of being able to steal other players' Sheep if a Celt player moves a unit close enough, even if the Sheep are close to other players' units. Celts cannot do the same to other Celts, however.
Like in Age of Empires II, the Sheep will fall under control to any player whose unit it comes into contact with. Originally introduced for livestock in Age of Mythology, the Sheep will fatten over time, which fills them with a much larger supply of food as time goes by. They start at 50 food and can store up to 300. This fattening process can be sped up substantially by tasking them near a Livestock Pen (Europeans), Farm (Native Americans), or Village (Chinese).
Sheep can also be trained at Livestock Pens and can be shipped from the Home City. They can also be found wild around most maps and even can be found as Treasures.
"Scientific Name: Ovis aries Approx. Size: 2 ft, at the shoulder, 100 lb. Diet: Grasses, sedges, lichen, mosses
Domesticated sheep have been kept by humans for thousands of years as sources of milk, wool, and meat. They are social creatures and gather in flocks, or mobs, known for blindly following the movement of their groups. In fact, there are distinct roles in the leadership of a mob. "Outliers" act as scouts and risk predation by ranging away from the herd in search of water and grazing. "Bellweathers" are sheep that watch the outliers and follow when it appears the outlier is safe. The rest of the flock then follows the bellweather. Sheep eat plants that other livestock will not and are now used in rotation with other livestock to maximize the grazing of pasture land and also as a form of natural weed control."