50 to 99 is Content. The animal will not attack you unless you attack first. 100 is Happy, but there is no difference between the two moods. Sometimes, when an animal hits an Enrichment Object like a Ball or Scratching Post, the mood will exceed 100 and will be shown as Content. Nothing bad happens, though.
-49 to 49 is Calm. Herbivores will only attack when provoked, and Carnivores will only attack when hungry. In the case of the Carnivores, this is averted with the very aggressive Spinosaurus, Sarcosuchus, Ceratosaurus, Liopleurodon, Mosasaurus, and Tyrannosaurus Rex.
-99 to -50 is Sad. The animal will attack everything on sight, regardless of whether it's hungry or not. -100 is Angry, but there is no difference between Sad and Angry.
HOW TO INCREASE A MOB'S MOODEdit
Give it an Enrichment Item.
Allow it to kill something. This raises its mood significantly, especially for Carnivores.
Eating a drop.
Placing enough of the same species near it.
HOW TO DECREASE A MOB'S MOODEdit
Placing too many or too little of the same species near it.
Placing incompatible species near it.
Letting it starve.
Being placed in a Hot Biome(Mammoths Only).