Kaliste, E. K., Mering, S. M., Satu, M. et al. 2006. Environmental modification and agonistic behavior in NIH/S male mice: Nesting material enhances fighting but shelters prevent it. Comparative Medicine 56(3), 202-208.

The aim of the study was to investigate effects of widely recommended nesting material and additional shelters on male mice. The aggressiveness of the mice in their home cages clearly increased in the nest group,as assessed by the number of wounds. .. The provision of a box or tube as a shelter, in addition to nesting material, prevented intracage fighting and did not lead to alterations in the weight gain or organ weights of the mice. However, the agonistic behavior of mice with shelters was slightly increased in behavioral tests. Anxiety in the elevated plus-maze was not affected by any of the housing systems. In conclusion, the agonistic behavior of NIH/S mice, an aggressive strain, seemed to be easily enhanced by these environmental modifications. The suitability of any enrichment should be carefully evaluated, especially when highly aggressive mice are used.