Behaviour studies were undertaken on three populations of free living American sheep, one being a Stone's sheep (Ovis dalli stonei) one a Dall's sheep (0. d. dalli) and one a bighorn sheep population (0. canadensis canadensis). The habitat-, body care- and social behaviour patterns - except those of mother and young - were described in detail. Each social interaction recorded was transferred to a computer card. 3800 interactions were analysed and form the basis of the quantitative data reported. American sheep show only minor quantitative differences in their social behaviour. However, behavioural differences within populations of the same species occur and appear to reflect population quality. Sheep evolution is conceived as follows: Sheep evolved from rupicaprid ancestors. They evolved large horns, pneumated skulls, lost or reduced display hairs, increased the size of the rump patch and increased sexual dimorphism. The damaging fighting forms of the rupicaprids were replaced by a ritualised form of combat. Sheep lost the thick hide as a defence mechanism, and defend themselves by catching the horn blow with their horned head. Skulls evolved to absorb concussion. The broadside display was replaced by horn displays. Ram horns function not only as weapons, but also as guards, display organs and rank symbols. Sheep appear to have evolved rapidly whenever they colonized new habitat in the wake of retreating glaciers. The expanding populations would experience intense selection for forceful clashing and larger horn size. Large horn size is a function of neoteny in rams. Rams mature sexually at 1.5 - 2.5 years of age, but do not mature behaviourally or reach ultimate growth form until they are 7-8 years old. Females are paedo-genic forms which remain similar in appearance and behaviour to sexually mature yearling rams. Neoteny also explains the long body growth of rams, the reduction and loss of the neck ruff, increased sexual dimorphism, the intense gre-gariousness of females and of juvenile rams, the increasing independence and leadership of rams as they grow older, and the more frequent use of aggressive patterns by bighorn as compared to thin horn sheep. Rams prefer to interact with rams of their own horn size and with females. They treat subordinates, irrespective of sex, much the same as they treat females. Rams change their behaviour not with the sex of the companion but with its dominance rank. The more that subordinate rams resemble females in appearance, the more they are treated sexually by dominant rams. Subordinate rams may act like females to the extent of urinating, or, assuming lordosis when mounted. Non-estrous ewes withdraw from rams, but estrous ewes remain and act like subordinate rams. Ewes are guarded and defended singly as they come into heat. They are followed by a group of rams. The largest horned rams guard and mount estrous ewes. Rams fight throughout the years, not for females, but for dominance. Despite intense competition, the dominant ram takes the estrous ewe away from the subordinate uncontested. Sheep changed primarily in social adaptations, which evolved quite independently of habitat - or body care adaptation. / Science, Faculty of / Zoology, Department of / Graduate

The biological activities of the neurohypophyses of pregnant and embryonic sheep, Ovis aries were studied. The levels of hormonal activities of the neurohypophyses varied with the stage of pregnancy, and were always lower than levels in the control (non-pregnant) glands. Chemical studies of the purified oxytocic and vasopressor moieties of the pregnant sheep have indicated that these agents are oxytocin and arginine vasopressin. An increase of biologically active agents of the posterior pituitary was detected concomitant with embryonic development. The amount of vasopressor activity greatly surpassed the oxytocic activity in the neurohypophyses of foetal sheep all through gestation, but the difference became smaller with the advancement of intrauterine life. Pharmacological and chemical studies indicated oxytocin and arginine vasopressin as the active peptides of the foetal neurohypophysis. In addition to these two neurohypophysial peptides characteristic of the mammals, the presence of a third peptide was indicated. Pharmacological studies indicate that this third neurohypophysial peptide of the foetuses may be arginine vasotocin, the antidiuretic principle of lower vertebrates. / Science, Faculty of / Zoology, Department of / Graduate

This study compared the foraging behaviour and nutrition of Stone's sheep (Ovis dalli stonei) which had access to burned range to that of sheep on unburned range throughout the year. In winter, sheep were restricted to areas with less than 25-30 cm of snow. For most sheep this meant windswept, alpine ridges, but one small population used a burned, subalpine slope. Grazing pressure was high on these restricted winter ranges, particularly during a severe winter, resulting in removal j of all the forage from alpine range, and leaving only very poor quality forage on the subalpine range. The poor winter nutrition was reflected in low fecal nitrogen and DAPA levels and high Protostronqylus counts. In spring, sheep used either natural or fire-induced subalpine clearings to obtain early new plant growth. Forage quantity was much lower on unburned ranges, but biting rate and foraging time were the same as on burned ranges with high forage biomass. Quality of available forage and food intake were also similar. The foraging behaviour of Stone's sheep appeared to be similar to domestic sheep in that intake rate was primarily dependent on grass length rather than forage density. Sheep moved to higher elevations as the season progressed which provided them with access to the higher quality alpine forage. Regular use of mineral licks in summer apparently satisfied their sodium requirement. Grasses and sedges were the most important foods throughout the year although forbs and browse were important in the summer. Adult mortality rates were low. Lamb production was low following severe winters, presumably due to poor nutrition. An explanation for changes in lamb production based on density-dependent selective feeding was developed. Burned ranges were of limited value to Stone's sheep because they were usually unavailable as winter range, did not provide superior spring range and were not used in summer. Horn growth, however, appeared to be slightly better on burned ranges. A model of nutrient intake is developed to investigate the seasonal pattern of nutrition on burned and unburned ranges. / Forestry, Faculty of / Graduate

The social organization and diurnal activity patterns of captive California bighorn ewes were investigated from May 1977 to December 1978. Social interactions between ewes were brief in duration and infrequent, relative to bighorn rams. Aggressive interactions (butts) were more common than horn displays. Although a dominance hierarchy was evident in the herd, it was not strongly linear. Age, horn length, and body weight were not shown to be strongly correlated to dominance. The most dominant animals proved to be the most aggressive, initiating more interactions than subordinate animals. The presence of a lamb appeared to improve the social status of some ewes. Dominant status could not be shown to positively affect an animal's diet, activity budget or productivity. The herd's diurnal activity pattern changed considerably on a seasonal basis. The activity pattern was characterized by successive feeding and bedding periods in spring and summer. Activity peaks generally declined in number and increased in duration during the fall and winter periods. The herd's diurnal activity budget also varied seasonally. The proportion of the day devoted to feeding increased with decreasing daylength, although actual daylight grazing times were poorly correlated to daylength. The proportion of the day devoted to bedding was highest in spring and summer, and to a lesser extent, in mid-winter. Actual bedding times were significantly correlated (r = 0.92) to daylength. Both the actual time and proportion of the day devoted to standing, travelling and "other" activities showed only minor seasonal fluctuations. It was shown that poor health in herd members affected activity budgets significantly. Late stages of pregnancy could not be shown to significantly affect activity budgets. Average basal metabolic rates (BMR) and diurnal activity costs were estimated for the herd. Both BMR's and activity costs were higher in spring and early summer than at other times of the year. / Land and Food Systems, Faculty of / Graduate

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