Behavioral observations.

Sexes and cage types are combined, for a total of 24 cages per strain/timeframe/density (2 sexes ×2 cage types ×6 replicates = 24 cages). The value represents the number of cages of the 24 in which the behavior was observed at least once during the entire 3-month or 8-month timeframe. For example, for strain 129, density group 1, whiskering and barbering were observed in 11 of the 24 cages during the 3-month timeframe and in 20 of the 24 cages during the 8-month timeframe. Alopecia was not observed in any of the strain 129 or DBA cages, regardless of density group or timeframe.
aFor details of floor space for each density group, see Table 1.
Behavioral observations did not differ significantly among density groups. Although behavioral observations did differ among strains, all values were within normal ranges.