I chose to use non-invasive methods to collect my data (behavioural data, feacal samples, and ano-genital odour samples via positive reinforcement training) both to avoid distress the study subjects (safeguard animal health) and to not affect the results. I avoided to use blood to analyse hormone levels and to capture animals to collect odour samples. In most cases I think we can opt for non-invasive methods, it is logistically more difficult but a better ethical choice - I believe.