The horses, donkeys, and camels do not refer to an ordinary travelling caravan but to the enemy's approaching army. The Persians included large numbers of donkeys and camels in their armies, both to carry the baggage and to confuse the enemy in battle. The watchman was instructed to listen closely when he saw this army approaching.
7 Elle vit de la cavalerie, des cavaliers deux à deux, Des cavaliers sur des ânes, des cavaliers sur des chameaux; Et elle était attentive, très attentive.