Figure 1

Circadian clocks are essential for survival of organisms under natural conditions. (A) Average survivorship of white-tailed antelope ground squirrels under semi-natural habitats. The animals were released in semi-natural habitat after surgical removal of their supra-chiasmatic nucleus (SCN) based circadian clocks. During the study period three out of five SCN-lesioned (SCN-X) individuals were predated upon as compared to two out of seven control animals. (modified after DeCoursey et al, 1997 [16]) (B) Average survivorship of free-living eastern chipmunks under natural environment. Free-living animals were captured from the study area and released back after surgical ablation of their SCN. The control animals were handled similarly and released back to the study area. During the eighty days of the study, more than 80% of SCN ablated individuals fell prey to weasels while mortality was significantly less in the surgical (sham) and intact controls. (modified after DeCoursey et al, 2000 [17])