Ontogeny of daily activity and circadian rhythm in the Iberian lynx (Lynx pardinus)

Abstract

The aim of this paper is to describe the ontogeny of the circadian activity rhythms in captive-born Iberian lynx (Lynx pardinus) from birth to subadult age and to verify if they develop a bimodal circadian pattern similar to the one they show in the wild. The amount of daily activity and the circadian rhythmicity of 61 Iberian lynx (48 mother-raised and 13 hand-reared) cubs were studied in two breeding centers. During the first month of life, the cubs were active 30% of the day. Activity increased up to 50% during the following two weeks, and then it remained constant until the end of the lynx physical development. The location of the breeding center affected the amount of daily activity of the cubs probably as result of different climatic conditions. Once the lynx cubs had completed their development, there was no difference in the time spent active between wild and captive lynx. Newborns had a constant level of activity throughout the day (24 h) during the first month of life. During the second month, once they had developed sufficiently to leave the den, a crepuscular bimodal circadian rhythm started to emerge. This pattern was completely defined by the third month of life. The overlap in circadian activity was over 0.88 when comparing the sexes, breeding centers and rearing methods. However, there was a significant difference between mother-raised and hand-reared cubs – the latter being more active in the morning–, as well as between breeding centers – again due to climate differences. Finally, an overlap of 0.85 in circadian activity pattern was observed between wild and captive lynx, although the wild animals were more active at night.