What are the early warning signs of ‘mean girl’ behavior?

“Mean girl” behavior refers to the intense, surprisingly common dynamic of interdog aggression among female housemates. Rather than starting with an outright fight, this tension usually emerges as the dogs reach social maturity (typically between 18 and 24 months of age).

Before a physical altercation occurs, you will usually see subtle challenges over social status, space, and control. The early warning signs of this “mean girl” behavior include:

• Controlling space and movement: The aggressor may restrict the other dog’s movement around the house by corralling them, doing random physical “body checks,” or shoving past them to get through a doorway first. They may also casually displace the other dog by standing in front of the water dish, blocking access to a bed or crate, or simply entering a room and staring at the other dog until the other dog leaves.

• Resource guarding and theft: The aggressive dog may steal the other dog’s toys, biscuits, or rawhides simply as a way to control them. You might also notice them guarding food bowls or actively protecting you from the other dog, effectively treating you like a highly-valued bone.

• Inappropriate physical domination: Watch for boundary-pushing behaviors where one dog puts their head, neck, or front paws over the other dog’s back for extended periods. They may also hump the other dog (from behind or over the head) or knock them down and lie on top of them until they “submit” and stop moving.

• Hostile body language: Subtle physical warnings include “dirty looks” (hard stares) and stiff postures. You might also notice pinned-back ears, a closed mouth with the corners pushed forward, or a stiff-legged face-off with their tail held unnaturally high. The challenger might also approach the other dog’s shoulders at right angles in a ritualized display.

• Changes in play dynamics: Play that turns tense is a major red flag, such as the dogs spending frequent, extended periods wrestling up on their back paws. It is also highly concerning if the play looks like bullying, causing the “victim” dog to watch the aggressor warily or to slink around the house to avoid them.

• Unprovoked threats: The aggressor may issue overt or passive threats, such as growling, snarling, or snapping at the other dog out of context or without a clear reason.

If you notice these behaviors, it is important to intervene early with behavior modification and management (such as separating them with gates or using crates when unsupervised) to prevent the tension from escalating into a dangerous fight.