Calm and exercise caging reduce stress hormone production. To assess biological stress levels we used an established noninvasive technique in which we measured CM levels in mouse fecal pellets (see Materials and Methods). (A) At d 0, before animals were placed in experimental caging, mean CM levels were similar in all groups. (B) After 14 d of housing in experimental caging, Calm, Cntl Ex and Calm Ex animals had significantly lower fecal CM levels compared with Cntl animals (Calm, Cntl Ex, P < 0.05; Calm Ex, P < 0.01). (C) At d 49, fecal CM levels from experimental animals had decreased further (Calm, Cntl Ex, Calm Ex, P < 0.0001). (D) At the 70-d endpoint of the experiment, fecal CM levels in experimental animals remained significantly lower than Cntl (Calm, P < 0.05; Cntl Ex, P < 0.001; Calm Ex, P < 0.01); note the change in scale to accommodate outlier. Data represented as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001.