Stress is an inseparable part of the life of each individual from every species. Even though we usually imagine predation and the fight for our own life, there are many types of natural stressors, for example an addition of a new individual into a stable social group (Fraňková et al. 2012). In spiny mice, stress levels depend on the position in the group’s hierarchy, there is also a discrepancy in basal stress hormone levels between commensal and non-commensal populations (Nováková et al. 2008). The level of stress hormones can be assessed from the blood or faeces of the animal. The measurements from faeces have one major advantage – they are non-invasive and in an apparatus we developed, the animal can remain in contact with the members of its group (Frynta et al. 2009). There are other non-invasive methods of stress assessment, for example, heart-beat, body temperature, or skin conductance measurements. At present we are developing a device for a heart-beat measurement of wild and moving animals of various species. Several standard behavioural tests are considered stressful (or in contrast non-stressful), nevertheless we often lack objective measurement of the physiological stress the animals actually experience in these tasks.