The progeny of crosses between individuals of two subspecies of Dicrostonyx groenlandicus, D. g. richardsoni, and D. g. groenlandicus were sterile, although both subspecies had previously been successfully bred in captivity. This laboratory experience may be of importance in the extreme changes in population of lemmings, in their classification as subspecies, and in procedures adopted when breeding in captivity.

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1972. Hibernation of eastern chipmunks (Tamias striatus) maintained under controlled conditions. Can. J. Zool. 50: 95-105.The hibernation pattern of captive eastern chipmunks maintained under controlled conditions of light and temperature was examined. It was consistent with the view that hibernation results from an endogenous rhythm with a periodicity of about a year, probably temperature independent.Continuous recording from nest bottom temperature sensors was tested for the first time with this species and found to be more accurate than the sawdust technique for detecting arousals. It also provided useful information about trends in body temperature.The hypothesis that a shift in the temperature at which heat-producing responses are mobilized occurs during hibernation and that it is responsible for the pattern of periodic arousals, is discussed in relation to the observations made. SCOTT, G. W., et K. C. FISHER. 1972. Hibernation of eastern chipmunks (Tamias striatus) maintained under controlled conditions. Can. J. Zool. 50: 95-105. Des tamias ray& ont kt6 gardbs en captivitk et soumis B des conditions contr8lks de temgrature et de luminositk pendant leur hibernation. Les rhultats de l'exp6rience s'accordent avec l'hypothhe selon laquelle l'hibernation est dktennink par un rythme endoghe B pkriodicitk quasi-annuelle, probablement indbpendant de la temgrature.Des sondes thermiques ? i enregistrement continu, utilisk pour la premikre fois chez cette espke, se sont avkrks plus efficaces que l'emploi du bran de scie pour determiner de f w n precise les moments d'kveil. On a pu aussi tirer de cette technique des renseignement utiles sur les variations de tempkitwe du corps.Ces observations ambent B discuter l'hypoth8se selon laquelle il se produirait u? dkplacement des seuils de temperature durant l'hibernatlon, un dkplacement responsable de la pblodicltk des moments d'kveil. SETOY, E. T. 1909.

No abstract