Changes in small mammal communities following logging were monitored in clear-cut and strip-cut upland black spruce (Picea mariana) stands and in selectively cut mixed wood stands in north-central Ontario. Clear-cutting and subsequent scarification essentially eliminated the vegetative cover. Much of the ground cover recovered within 5 years and shrubs within 12 years, but mosses and lichens took much longer. The small mammal community in both clear-cut and strip-cut stands changed over the first three years after logging from one dominated by southern red-backed voles (Clethrionomys gapperi) to one dominated by deer mice (Peromyscus maniculatus) and then remained relatively stable for up to 13 years after harvest. That shift was not apparent in selectively cut mixed wood stands where the composition of the small mammal community was similar between uncut stands and stands 4–23 years after harvest. There was relatively little change in total numbers of small mammals after logging. In general, the diversity and evenness of small mammals increased or remained stable in the first 1–3 years following harvest, decreased on older (3–16 years) cuts, and then increased to values similar to those in uncut stands on the oldest (19–23 years) cuts.

Populations of Clethrionomys gapperi and Peromyscus maniculatus were investigated on newly harvested upland black spruce (Picea mariana) clear-cuttings and in control areas (uncut, selective cut, older clear-cuttings) near Manitouwadge, Ontario. On control areas Clethrionomys had increased breeding intensity, better summer survival rates, and a relatively greater number of young in 1978 relative to 1976 and 1977. Those conditions appeared to be unrelated to summer weather and occurred after a cold, wet spring with a delayed snowmelt. Numbers of Clethrionomys on new clear-cuttings declined to nil over the first two summers following timber harvest. Demography on new clear-cuttings was similar to that on control areas except for poorer juvenile survival rates and fewer young. The disappearance of Clethrionomys from recent clear-cuttings was likely due to direct mortality. Demography of Peromyscus on control areas was similar each year except in 1978 when there was an increase in the breeding intensity of males and a decrease in the proportion of young. Numbers of Peromyscus on new clear-cuttings increased over the 3 years. Demography was similar on clear-cuttings and control areas in 1978, but in 1976 and 1977 the clear-cutting population had an excess of males, greater reproductive intensity of both males and females, more wounding of males, and less wounding of females. A highly mobile, young, male-dominated population with a high reproductive rate and a good summer survival rate was present on the 1- and 2-year-old cuts. Recent clear-cuttings in upland black spruce act as dispersal sinks for Peromyscus and provide new habitat for colonization by presaturation dispersers.

Captures of Dicrostonyx groenlandicus on northeastern Devon Island peaked in 1969 and 1973, were higher than expected in 1971, and were minimal (< 5 per 1000 trap-nights) in 1970 and 1972. Captures declined from July to August in at least five of seven summers and may have declined in a 6th year (1973). No change was detected in 1972. Body size was maximal in 1973 for mature and immature males and females and for all pelage (=age?) classes. Sexual maturity was delayed, at least in males, in 1973. Wintering females conceive under the snow in May and the litter is weaned at the normal time of snowmelt. Two other summer cohorts are produced by surviving old females and early maturing females of the first litters. None of the late summer cohort matures before the onset of winter. No female examined bore more than two summer litters. Mean summer litter size was 5.7 with no significant variation between years. Mean sex ratio was 50.3% male. It is suggested that density-related effects ought to occur in winter, rather than summer, but evidence on this point is equivocal. Arctic adaptations of D. groenlandicus are discussed.

We biochemically analyzed and characterized the genetic structure of a population in danger of extinction ,"Alberes", a local cattle breed of the Catalonian Pyrenees (Spain and France). Ninety-two individuals were analyzed for five polymorphic genetic loci (Hb, Alb, Tf, Gc and Ptf2). The animals were grouped according to coat color: Fagina Alberes variety (N = 39) and Black Alberes variety (N = 53). The genetic structures and relationships between these subpopulations and one "outgroup" breed ("Bruna dels Pirineus") were analyzed and compared by using F-statistics. We determined that inbreeding in the Alberes breed is not significant, since negative and nonsignificant F IT and F IS values were obtained. The average genetic differentiation between subpopulations within the Alberes breed was 1.5% (F ST = 0.015; P < 0.05), with an effective number of 4.1 individuals exchanged between subpopulations per generation (gene flow). The results obtained in this study corroborate the potential danger of extinction of the breed. The Black Alberes variety is proposed as the principal nucleus of genetic conservation for this breed, as it seems to show a higher degree of genetic isolation from other foreign populations.

Our working hypothesis was that winter mortality of Clethrionomys rutilus would be more severe in tundra than in taiga, and in winters with "unfavorable" rather than "favorable" conditions during establishment or ablation of the snow cover or in the subnivean environment during midwinter. Vole mortality was higher in the tundra (90–95%) than in the taiga (55–75%), in accordance with our prediction, but year to year differences in snow conditions were not necessary determinants of winter survival during the 4 years of the study. Subnivean breeding was never detected. The onset of summer breeding was related to the time of snow melt, and a late spring was followed by a low rate of maturation of young-of-the-year females and small spring-to-fall increase in numbers. Few young of either sex matured in two of three summers in the taiga, whereas about half the females and one-third of the males matured each year on the tundra. Litters were significantly larger on the tundra and spring sex ratios were female biased. Thus reproductive output was high on the tundra, which would offset high winter losses. Intraspecific wounding was related to density and maturity except that on the tundra many immature young had bites. No superannual fluctuation was apparent on the tundra.