Fig. 3

Stability of REIMS signatures to storage conditions and diet. Faecal pellets from captive-bred house mice were stored for up to 28 days under ambient temperature (average 18 °C), either in closed tubes or open to the environment. Further samples were stored for the same period in closed tubes at − 18 °C, 4 °C or 20 °C (a). All samples were then analysed by REIMS, and the classification accuracy under the different conditions was assessed by random forest analysis relative to baseline house mouse data taken from samples stored for 1 day at 4 °C (marked with an asterisk, b). To assess the effect of diet on the REIMS signature, house mice, initially fed a standard laboratory rodent 5FL2 EURodent Diet (white bars), were acclimated to a new diet over 1 week when they had access to both the old and new diets (week 0) before being transferred solely to the new diet for a further 4 weeks (c). Faecal pellets were collected at weekly intervals. Classification accuracy, assessed by random forest analysis, was relative to the baseline data from day 0 of the study (marked with an asterisk, d)