We adhered to the "Guidelines for the use of animals in research" as published in Animal Behaviour (1991,41,(183)(184)(185)(186). The Academic Committee of the Programa de Doctorado en Ciencias Biológicas y de la Salud, UAM-X (Universidad Autónoma Metropolitana-Xochimilco), approved the experimental protocols and the handling of non-human animals. Maximal care was taken to avoid animal disturbance during faecal sampling and behaviour video-recording. All **data** in this study are available from the corresponding author.