Evidence for ecological adaptation of circadian systems : Circadian activity rhythms of neo-tropical bats and their re-entrainment after phase shifts of the Zeitgeber-LD.

Comparative studies on the circadian activity rhythm of five neotropical bat species show, that even exclusively tropical Chiroptera yield considerable differences with respect to their light-induced variation of the period length and the time needed for re-entrainment after phase shifts of the Zeitgeber-LD (Figs. 2 and 3). Species with a wide variation range of the period length resynchronize very fast and vice versa. Both reactions suggest the circadian system to have a higher plasticity or a higher sensibility for the exogenous components respectively. The sensibility for these exogenous components is, according to the hitherto results, in general higher within insectivorous Chiroptera species than within frugivorous/nectarivorous to omnivorous species. It is discussed, whether this can be interpreted as a specific adaptation to the demands of a predatory way of life.