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aout. Sg MEMES ea. ae EN, , 5. Circannual Rhythms . ;, The t ircannual rhythm is coined for rhythms that persist and recur annually with the, Ter (one year). Annual periodicity in reproductive, , free-running period of approximately 365 days nd mammals. For example, in its, , i i s, birds a, cycles have been observed in many insects, fishes, : £ tin 7, natural habitat the ‘carpet’ beetle Anthrenus verbasci feeds on the organic matter in old birds, , i Vv . slake ad 59) showed, year to com lete its de elopment B 9, nests and takes one, two or even three yea Pp ' :, , that the development of this insect comprised success A, diapause for i winter passed. The atucal period of this circannual rhythm (41-46 weeks), could be entrained to an exact annual cycle by the naturally occurring changes in the day length., , Among fishes, brook trout spawn in the fall; bass and blue gills in late spring and summer., Among birds, some of the best examples of circannual clocks are shown by warblers and whitecrowned sparrows. Among mammals, circannual rhythms control activity and hibernation cycles,, e.g., hedgehog (Erinaceus europaeus), rodents, ground squirrels (Spermophilus spp.) and, , chipmunks (Eutamias)., , hibemation, hibernation, activity, hibemation, hibernation, , , , , , Animals, oo, , , , , , , , , , , , Years, , Fig. 13.4. Circannual cycle of the golden-mantled ground squirrel. Animals held in constant darkness and at, constant temperature nevertheless entered hibernation at certain times year after year., , , , oY Silt, , Scanned with CamScanner

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sjogical Rhythms 315, , Testing the hypothesis that an animal has a circannual rhythm is technically difficult because, dividuals must be maintained under constant conditions for at least two years after their removal, om the natural environment. One successful study of this sort involved the golden-mantled, ound squirrel (Pengelley and Asmundson, 1974) of north-temperate North America. This, quirtel in nature spends the late fall and winter hibernating in an underground chamber. Five, nembers of this species were born in Captivity, then blinded and held thereafter in constant, iakness and at a constant temperature while supplied with an abundance of food. Year after, year, these ground squirrels entered hibernation at about the same time as their fellows living in, he wild (Fig. 13.4). ‘3, , Several behaviours of animals, thus, have been cyclic or rhythimic, e.g., 1. eating and, itinking; 2. sleep and activity; 3. learning and memory. ao, , , , , , , , Scanned with CamScanner