The population dynamics of caribou (Rangifer tarandus) on the Island of Newfoundland were studied 1957 to 1967. Four herds were recognized and censused: the Northern Peninsula — 450 animals in 1958 and 400 in 1966, the Avalon Peninsula — 125 in 1957 and 720 in 1967, the Humber River — 130 in 1956 and 115 in 1964, and the Interior -- 4600 in 1957 and 6200 animals in 1966. The Island population 1900-1910 was estimated at 40,000 animals. After 1915 these herds rapidly declined and reached a low of perhaps only 2000 animals by 1930. The annual rate of increase (r) of all the herds was low. The Humber and Northern Peninsula herds showed no increase while the Interior Herd grew at only 0.044. The Avalon Peninsula Herd showed the greatest rate-of-increase 1961 to 1967, r= 0.120. The potential r of Newfoundland caribou is probably greater than 0.30. A herd of caribou introduced to Brunette Island increased at r=0.352, from 17 to 100 animals in 5 years. In the Interior Herd, birth rates were high and constant and averaged 0.85 calf per doe 2-years-of-age and older and 0.94 calf per doe 3 years and older. Natural mortality rates were low beyond 6-months-of-age. They were 4 per cent for does, yearlings, and calves and 9 per cent for stags 2-years-of-age and older. The kill of stags by hunters was 11 per cent and reduced the proportion of stags in the population. The survival of calves to 6-months-of-age was strongly correlated with growth of populations and appeared the main influence on numbers (correlation coefficient r=0.922, P<0.01). The mortality of calves in the first summer was high; an average of 69 per cent died in the Interior Herd and in the Avalon Peninsula Herd 30 per cent of the calves died. The major cause of mortality of calves was apparently predation by lynx (Lynx canadensis). As early as 2 weeks after calving, 27 per cent of the calves were missing. They were apparently dragged into forest cover by lynx. Of 114 dead or morbid calves located 74 per cent were bitten by lynx, escaped and had developed cervical abscesses from infections of Pasteurella multocida. The two major factors limiting populations of caribou in Newfoundland 1900 to 1967 appeared to be lynx predation of calves and shooting mortality of adults. Poor recruitment and high loss to hunting probably caused the decline of the herds 1915 to 1930. The primary factor limiting numbers in the Interior and Avalon Herds, 1957 to 1967 was lynx predation of calves in their first summer. Illegal hunting was probably important in the Northern Peninsula and Humber River herds 1957 to 1967. / Science, Faculty of / Zoology, Department of / Graduate

The object of this study was to compare the role of changes in reproduction and mortality in regulating population density in the deer mouse, Peromyscus maniculatus, and if possible to discover some of the factors affecting the reproductive rate. Observations were made on natural and experimentally reduced populations on the University Endowment Lands in 1964 and 1965. In both years numbers remained relatively steady during the summer, increased in the fall, when immature animals replaced the adults, and gradually declined over the winter. Animals were about equally abundant at comparable times in both years, fall densities being about 4.72 mice per acre. The stationary state of these populations was associated with a poor reproductive performance on the part of the females, whose breeding success varied between areas, and was greater in 1964 than in 1965. No change in litter size or in prenatal loss was observed during the period of study. The males, in contrast, were sexually active from March to September on all areas in both years. The greatest loss of mice occurred between birth and age at first capture, after which juveniles survived at the same rate as the adults. Survival was poorer during the breeding season than during the winter, and survival of males was poorer than that of females. Populations whose numbers had. been experimentally reduced and whose age structure had been altered, were not significantly different from the natural populations in mean monthly body weights, reproductive performance, or survival. Mean monthly body weights and reproductive performance were lower, and survival of the young from birth to age at first capture was higher in 1965 than in 1964. The proportion of subadults which became fecund was greatest on this area in 1964. The stationary state of these populations was maintained by changes in survival rather than by changes in reproductive rate. The reproductive performance of the females was fairly constant whereas the loss of young from birth to age at first capture varied. Loss of the young is attributed to their death or emigration in response to aggressive interactions within the population. / Science, Faculty of / Zoology, Department of / Graduate

Sadleir (1965) proposes that the survival of juvenile deermice is determined by the aggressiveness of the adult population. During the summer, when adult aggression is high, juvenile survival is poor, but in the fall, when adult aggression is low, juveniles survive well. The purpose of this study is to examine some of the consequences of Sadleir's hypothesis experimentally. Sadleir bases his hypothesis on the observation that the aggressiveness of males changes seasonally. This premise has been reexamined and confirmed. How adult aggression affects juveniles was studied first in the laboratory. Juveniles grow poorly when competing with adults in their home cage. Males appear to be more active aggressors than females, but only aggressive males are capable of inhibiting juvenile growth. Even though juveniles grew slowly when competing with aggressive adults, they seldom died from encounters with adults. In order to avoid the crowded conditions and confinement implicit in the laboratory experiments, the relationship between adult aggressiveness and juvenile growth and survival was reexamined in field experiments. Two partly isolated plots of habitat were used, and on these plots artificial populations of aggressive or docile male deermice were established. Juveniles were then released onto the plots, and their growth and survival followed. In the field, as in the laboratory, juveniles grew poorly when competing with aggressive adults. Since emigration was not restricted in the field, however, juveniles disappeared in significantly greater numbers when the adult population was aggressive than when the adult population was docile. In addition to these experiments, the success of immigrants onto trapped out plots and plots with a resident population was examined. Immigrants were more successful in establishing themselves on trapped out plots. All the data collected support Sadleir's hypothesis, and it seems reasonable to conclude that the correlation he drew between adult aggressiveness and juvenile survival is real. However, the data collected also provide some interesting clues as to the organization of deermouse populations. An organization is proposed in which the social unit is an animal and its immediate neighbours. Within the social unit mutual antagonism is reduced. But the members of the unit maintain a high level of aggressiveness, and are intolerant of any stranger that wanders into their home ranges. The system proposed would prevent immigrants from settling, while conserving energy by reducing antagonism between familiar animals. The system would also effectively regulate population size. / Science, Faculty of / Zoology, Department of / Graduate

A number of studies on small mammals have shewn that changes in the frequency of alleles at polymorphic loci are correlated with population fluctuations. To determine whether this association between demography and genetics is causal, I altered gene frequencies in two field populations of M. townsendi Using starch gel electrophoresis, I detected a leucine aminopeptidase (LAP) polymorphism in M. townsendi. The fast allele, LAP-F, was present in a control population at a frequency of about .35 from July 1971 to July 1973. By removing homozygous SS voles from one experimental population I maintained an LAP-F frequency of about .75. Removal of FF homozygotes from a second population resulted in an LAP-F frequency of about .25. I monitored demographic variables of the populations while the selection was being applied. The populations went through increasing and peak phases and then declined sharply during the spring of 1973. There were indications that different genotypes had an advantage in survival and reproduction during different phases of population density. The selection that maintained the polymorphism on the control area could be correlated with population density. However, the overall fitness of each experimental population was not affected by its genotypic composition at this locus. / Science, Faculty of / Zoology, Department of / Graduate

The population dynamics of Microtus townsendii in a linear habitat were monitored weekly for one year (June, 1971-August, 1972). Demographic characteristics such as location on study area, sex, weight (age), reproductive condition, and survival were recorded weekly. An Intensive study of early Juvenile survival was also undertaken. The population was observed to decline in the spring of 1972 from peak densities the previous summer and early spring. The decline did not appear to result from decreased reproductive effort or dispersal, but could be explained solely on the basis of mortality. Several observations were made which did not follow the usual demographic trends in microtine population biology. Extremely high densities with small home ranges for individuals were found on the linear study area as compared with areas of continuous habitat. This population became sexually mature at much lower body weights than other populations of Microtus townsendii in the area and average body weights were lower, although growth rates were comparable. / Science, Faculty of / Zoology, Department of / Graduate

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Thesis (PHD)--University of Montana, 2009. / Contents viewed on December 22, 2009. Title from author supplied metadata. Includes bibliographical references.

Thesis (Ph.D.) - University of St Andrews, May 2007.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.