Laboratory mice are well capable of performing innate routine behaviour programmes necessary for courtship, nest-building and exploratory activities although housed for decades in animal facilities. We found that in mice inactivation of the clock gene Period1 profoundly changes innate routine behaviour programmes like those necessary for courtship, nest building, exploration and learning. These results in wild-type and Period1 mutant mice, together with earlier findings on courtship behaviour in wild-type and period-mutant Drosophila melanogaster, suggest a conserved role of Period-genes on innate routine behaviour. Additionally, both per-mutant flies and Period1-mutant mice display spatial learning and memory deficits. The profound influence of Period1 on routine behaviour programmes in mice, including female partner choice, may be independent of its function as a circadian clock gene, since Period1-deficient mice display normal circadian behaviour.

It has been brought to our attention that the data analysis for figures 1 and 2 is not appropriate. The colleague who contacted us correctly remarked that we should have compared the mean frequencies of the two genotypes, instead of all calls of all animals in the genotypes, because the genotype is the decisive parameter ('The decisive number for calculating the mean + s.e.m. for each column is the number of animals, not the number of calls. Therefore, the calculations and the statistics are misleading'.).All ultrasound vocalization (USV) data regarding frequency and amplitude have therefore been re-analysed accordingly, the figures were revised and corrected and all frequency and amplitude data are now provided together with the statistical data and the analysis procedure. In brief, we first took the data from the automated analysis provided by AviSoft SASLabPro for USV parameters (start-, peak-, end-frequency, start-, peak-, end-amplitude, etc.) and calculated a mean value for each parameter of each individual mouse (see the electronic supplementary material, tables S1-S3). These mean values were then tested for Gaussian distribution (normality) with the Kolmogorov-Smirnov test with Lilliefors-modification. If the normality-test was passed, we compared the genotypes by Student's t-test, if not by an appropriate non-parametric test, e.g. Mann-Whitney U-test. All p-values are 'given per comparison'. Results (a) Ultrasound vocalization frequency and amplitudeWT (N ¼ 6) and Per1 2/2 (N ¼ 16) mice showed differences in the maximal and minimal peak frequencies (figure 1) and the peak amplitude of USV (figure 2) when confronted to a WT female. At day 2 (figure 1a), the mean maximal peak frequencies of each entire element (USV call) that was detected of the WT (81.1 + 8.0 kHz) differed from the Per1 2/2 (74.0 + 9.9 kHz) animals. The minimal peak frequencies were significantly different and, similar to the maximal frequencies, lower in Per1 2/2 compared to WT (WT: 68.0 + 4.7 kHz; Per1 2/2 : 60.7 + 7.3 kHz; p 0.02 t-test).