Scales, M., McDonald, K. M. 2011. Factors influencing the preferred nesting location of laboratory mice. American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 773 (Abstract #P128).

Understanding the preferred nesting location of laboratory mice within the cage may serve as a useful, objective, behavioral assessment tool. To determine if caging ventilation rates influenced nesting location, we observed nesting site (front, middle, or rear) within the cage, in static, low velocity (30 ACH), and moderate velocity (70 ACH) airflow caging. We observed that 60.66% (n = 244 boxes) of mice housed in static caging preferred to nest in the rear of the cage, compared with 48.66% (n = 187 boxes) of mice in low ventilation caging, and only 14.02% (n = 635 boxes) in moderate ventilation caging. These data suggest that mice tend to nest distally from the source of forced air. To determine if we could mitigate the mice’s nesting preference in ventilated caging we placed nesting material in the rear of the cage and observed the nesting site 24 h later. Placement of the nesting material in the rear of the cage did not significantly increase the proportion of mice that nested in the rear of the cage, in either low ventilation caging (Z = 0.148, P = 0.882) or moderate ventilation caging (Z = 0.253; P = 0.800). Breeding conditions may, however, mitigate nesting preference. In moderate ventilation caging, we observed that mice with newborn pups nested significantly more often in the rear of the cage (Z = 5.53%, P < 0.01), when compared with mice without litters. The data suggest that some environmental factors do influence nest site location, and that future studies should evaluate the effects of other macroenvironmental stressors on nesting behavior.