Overview and Meaning
The area in a cage is divided up by mice for specific purposes. While feeding and drinking areas are predetermined by the placement of food hoppers and water bottles, mice divide and appoint some of the remaining space for sleep and waste evacuation areas (usually on opposing sides of the cage). When mice live together in group housing, they usually sleep together in the designated sleeping area. Occasionally they will sleep alone; but usually that is because the sleeping mouse chooses to be inactive, while the rest of the group is active.
Mice will sleep together for physiological and psychological reasons. In general, mice prefer a warmer ambient temperature during the light phase, and the light phase is when mice tend to sleep the most. Therefore, even though a laboratory room is temperature controlled, mice may congregate to help regulate their body temperatures during a period of inactivity when their body heat lowers or because housing conditions are too cold. Sleeping together is also for comfort and security, which is partially instinctual and may be motivated by the occasional intrusion by cage handlers. (Gordon, 2004).
Sleeping that occurs with two or more mice.
Affiliative behaviors are social interactions that function to reinforce social bonds with a group or which are of mutual benefit to all animals involved in the interaction.
When mice are sleeping together, there are two possible conformations, these conformations usually occur together or sometimes separately: