Skip to main content


Bared teeth is a behavior which occurs when a mouse displays its teeth to another mouse during an agonistic interaction.


Bared teeth is an agonistic behavior. It is sometimes referred to as open-mouth tooth display and occurs when a mouse shows its teeth to another mouse.

When the teeth are barred the mouse is open and the teeth at the base are revealed. It is also possible to reveal all of the bottom incisors. When the expression is really intense, more teeth can be seen because the mouth gets wider.

A more intense version of bared teeth can be seen when there is a nose-off between two mice. The mice are aggressively facing each other and the mouth is completely wide open, making a “V” shape and revealing the lower incisors. Sometimes hissing or squeaking sounds are let out. Furthermore, the ears may be rotated forward and slightly down while the forehead will seem flattened.

Bared Teeth Can Be Expressed with Hissing

The more aggressive version of bared teeth, as mentioned previously, can be seen during a nose-off interaction between two mice. The mouth is open and the incisors are revealed.

Noises, like hissing, may be emitted and the ears will be pointing downwards while the forehead will look as if it has been flattened. The more intense version of bared teeth does not just include displaying more teeth by opening the mouth widely, but it includes additional alterations in the facial expression.

Bared Teeth in Other Animals

Bared teeth is a display that can also be observed in other animals within the animal kingdom, such as monkeys or dogs, and it is not specific to mice.

Current research on baring teeth is predominantly conducted using primates, seeking to distinguish between dominant and submissive instances of this behavior, since so much remains unknown. This research could eventually serve as a good starting point for future research using rodents.

Function of Bared Teeth

  • As a warning signal. By using bared teeth as a warning signal, a mouse can display potency when it senses that it is being challenged or provoked without immediately resulting to fighting, thus saving energy and increasing chances of survival.
  • To demonstrate readiness to fight. Bared teeth, in an agonistic context, demonstrate to another animal the intention to fight or continue fighting. Therefore, it is an aggressive display that does not require a lot of energy and risk (such as biting does, for example) and, thus, enables the mouse to challenge or threaten another mouse easily.

Application of Bared Teeth

  • In a threatening situation. Bared teeth may be observed when a mouse is in a threatening situation or when it wants to threaten another mouse.
  • During agonistic encounters. When a mouse is in an agonistic encounter, bared teeth, amongst other aggressive behaviors, will be exhibited.

Behavioral Tests for Assessing Bared Teeth

Bared teeth is likely to be observed during any behavioral test which requires confrontation between two mice in which at least one of the mice might react aggressively.

  • The Tube Dominance Test. In this test, two mice brought together in a conflict situation, bared teeth may be displayed along with other aggressive behaviors in an attempt to exert dominance.
  • The Resident-Intruder Test. When a mouse which is the “resident” in its own cage is confronted with another mouse that is the “intruder,” bared teeth may be observed as a result of the interaction between them.
  • The Standard Opponent Test. In this test, two mice which are strangers to each other are placed together in a cage and observed for an allotted period of time. Aggressive behaviors, including barred teeth, are subsequently counted and tallied, in order to quantify social dominance.
  • The Sociability Chamber. The Sociability Chamber is used to detect sociability levels between two mice. However, if a mouse is aggressive in nature, it might react threateningly to the other mouse and display its teeth.


  • Bared teeth is a behavior exhibited when mice expose their teeth to another mouse. The teeth display can be wide or narrow.
  • Bared teeth is a behavior associated with aggression.
  • Sometimes noises or squeaks are combined with the teeth display.
  • Bared teeth can be threatening and are typically observed in agonistic situations and encounters.
  • In tests like the Tube Dominance Test, where mice face a confrontational situation, bared teeth are likely to be shown. Other behavioral assessments which may detect bared teeth instances include the Standard Opponent Test, the Sociability Chamber, and the Resident-Intruder Test.
  • More research needs to be conducted on the bared teeth behavior in mice, since most of the current research is geared towards primates.


  1. National Research Council (US) Committee on Recognition and Alleviation of Distress in Laboratory Animals. Recognition and Alleviation of Distress in Laboratory Animals. Washington (DC): National Academies Press (US); 2008. Appendix, Tools to Monitor and Assess Health Status and Well-Being in Stress and Distress. Available from:
Close Menu