Ultradian Rhythms of Body Temperature Are Associated with Temperament in Greenfinch (Chloris chloris, Fringillidae, Aves).

Previously, in male Greenfinch, we have described ultradian rhythms of body temperature with periods of 3-6, 8-10, 12-20, and 40-60 min. There are individual variations in this rhythmicity. Rhythms with a period of 3-7 min are more characteristic of some males but not for the others. These males had small values of the ratio of the harmonic spectral density in the range of 12-20 min to the harmonic spectral density in the range of 3-7 min. In this study, we hypothesized that ultradian rhythmicity of body temperature fluctuations is related to the nervous system activity in general and to temperament in particular. We have conducted two sets of experiments for estimating the aggression level (n = 12 males) and reaction to novelty (n = 17). Individuals with predominant rhythms with a period of 3-7 min are less aggressive and more slowly adapt to new conditions. Thus, the ultradian body temperature rhythmicity in Greenfinch is related to their behavioral features and temperament.