Multivariate analysis of temporal descriptions of open-field behavior in wild-derived mouse strains.

The open-field test is a commonly used apparatus in many behavioral studies. However, in most studies, temporal changes of details of behavior have been ignored. We thus examined open-field behavior as measured by both conventional indices and 12 ethograms supported by detailed temporal observation. To obtain a broader understanding, we used genetically diverse mouse strains: 10 wild-derived mouse strains (PGN2, BFM/2, HMI, CAST/Ei, NJL, BLG2, CHD, SWN, KJR, MSM), one strain derived from the so-called fancy mouse (JFI), and one standard laboratory strain, C57BL/6. Conventional measurements revealed a variety of relationships: some strains did not show the hypothesized association between high ambulation, longer stay in the central area, and low defecation. Our ethological approach revealed that some behaviors, such as freezing and jumping, were not observed in C57BL/6 but were seen in some wild-derived strains. Principal component analysis which included temporal information indicated that these strains had varied temporal patterns of habituation to novelty.