2020 updates by Cathy Bickel
Signs of aggression between gerbils, in escalating order of seriousness:
- Scent-gland marking
- Over-aggressive grooming accompanied by squeaking by the gerbil being groomed
- Mounting behavior
- Aggressive posturing, where a gerbil fluffs up his fur and curls sideways, keeping his side facing his opponent, similar to aggressive behavior between cats
- Wagging or whipping their tail side to side.
- Chasing around the tank with the victim running away
- Chasing with the victim leaping in the air
- A "ball fight," where two gerbils roll in a ball like in a cartoon
Milder forms of gerbil-to-gerbil aggression can often be diverted with a new toy, box, or tube, or some playtime out of the tank. Overcrowding is a possible cause. Aggression is more likely among groups of three or more. Age can be a factor; fully mature gerbils are more likely to become territorial. The scent of a female in heat can provoke aggression between otherwise peaceful males. One gerbil is normally more dominant than the other and this is not a problem for them unless it escalates to the point where someone gets hurt. See Declanning for more information.
Aggression toward humans is highly unusual in gerbils. Gerbils who bite are more likely to be fearful than truly aggressive. See Biting.