The Mountain Bull was originally brought to the Frostfangs alongside the early Numenorian settlers into the valley, and was abandoned in the valley after the Numenorians defeated the White Walkers and sealed the valley off. This means that the Mountain Bull is the direct relative of the Cliff Bull of the Valley of Lucerne, and other then being a tad bit larger is nearly identical.
Mountain goats are herbivores and spend most of their time grazing. Their diets include grasses, herbs, sedges, ferns, mosses, lichens, and twigs and leaves from the low-growing shrubs and conifers of their high-altitude habitat. In captivity, the mountain goat's diet can also include grain, alfalfa, fruits, and vegetables.
Nannies can be very competitive and protective of their space and food sources. They will fight with one another for dominance in conflicts that can ultimately include all the nannies in the herd. In these battles, nannies will circle each other with their heads lowered, showing off their horns. As with fights between billies during breeding season, these conflicts can occasionally lead to injury or even death, but they are largely harmless. To avoid fighting, an animal may show a posture of nonaggression by stretching low to the ground.