Some animals lose the herd entirely. The animals change directions more often without as much reason as they will find themselves grazing territory already grazed without success. Animals are more sensitive and fights break out between members of the group. Mating becomes more competitive. At the final levels of stress and starvation the herd barely exists as a group anymore.
Animals become disoriented and find themselves isolated.
Sexual activity stops. Some parents will ignore their young. Senses of sight, sound, scent are heightened in the hunt for food. Food, if found, would taste better as well. Animals no longer sleep and graze through the night.