ENVIRONMENT
In addition to bedding, other factors within the limits of the cage itself constitute the so called "microenvironment". Hamsters respond socially and sexually to chemicals called "pheromones" which are excreted in the urine and give off a characteristic odor that other animals can detect. Hormones influence both sexual activity and territorial boundaries.
Rodents will reestablish their social hierarchy after they have been placed into a cage with clean bedding. This may result in injuries from fighting - nevertheless, cages must be routinely changed because research animals need to be kept in dry, comfortable conditions.