For the polar bear (<i>Ursus maritimus</i>), a terrestrial carnivore on the highest trophic level in the Arctic marine ecosystem, periods of nutritional restriction or fasting are a characteristic feature of an annual cycle. The overall objective of my thesis was to examine some of the effects of such a 'feast-or-fast' feeding pattern on the body composition, body size and reproductive performance of this Holarctic ursid. As a reproductive strategy, pregnant polar bears occupy maternity dens for up to 6 months between late summer and spring. While in dens, maternal nutrient stores meet all maintenance energy requirements and sustain the nutritional demands of gestation and early lactation. I quantified the nutritional costs of this prolonged 'reproductive fast' in polar bears and examined the effects of variation in maternal body condition on reproductive performance. While fasting, body mass decreased by 43% and of the change in body energy content 93% was attributable to loss of fat. Bears that were fatter priorto denning produced heavier cubs, which would be more likely to survive. Much of the variation in body condition prior to denning was accounted for by age, older females being in better condition. Using an index of milk quality that was closely related to daily milk energy yield, I investigated the independent effects of maternal body condition and age on lactation. Irrespective of condition, older bears tended to produce higher quality milk. While lactation in polar bears is clearly sensitive to body condition, these results also provide strong support for an age-specific increase in reproductive effort among females. Body size is typically a strong determinant of male reproductive success in polygynous mammals such as polar bears. Consequently, theory predicts that mothers in good condition should invest more in male than female offspring in-order to produce large adult males. An underlying assumption of this theory, however, is that early differences in body size among male offspring, such as those apparent by the end of maternal care, will affect their relative adult body size. I tested the validity of this assumption in polar bears and found that, in comparison to females, variation in body size among 2-year-old males was a weak determinant of adult size. I suggest that, in comparison to females, a longer period of growth after maternal care may predispose the adult size of males to a greater degree of environmentally mediated variation. This lack of persistence in relative body size would limit the ability of mothers to affect the adult size of their male offspring, and thus reduce the effectiveness of sex-biased maternal investment as a reproductive strategy in polar bears. One of the principle physiological adaptations enabling animals to go without food for prolonged periods seems to be a heightened ability to minimize the net catabolism of body protein. I quantified changes in the body composition of free-ranging polar bears during the ice-free season. In contrast to previous studies on fasting bears, catabolism of protein appeared to meet a significant proportion of maintenance energy demands in some individuals. (Abstract shortened by UMI.)

Muskoxen (<i>Ovibos moschatus</i>) are relatively large herbivores living in an arctic environment where forage is sparse and its availability during long winters is often much reduced by snow and ice. Muskoxen cope by obtaining energy and nutrients from the low-quality sedges and grasses they eat, and from body reserves accumulated in summer and autumn. The objectives of this study were to evaluate the physiological and energetic adaptation of muskoxen to digestion of graminoid forage, and to measure the extent and reproductive significance of seasonal changes in body composition of female muskoxen. The first objective was addressed using two studies with captive muskoxen in Saskatoon, and the second during a field study on Victoria Island, Northwest Territories. In the first study, changes in body weight, intake, retention time and digestibility of a supplemented brome-alfalfa hay were measured in mature muskoxen during two seasonal cycles. Mean daily dry matter intake of breeding females was highest in July and August (62 ± 3.6 g/kg^0.75) then declined slowly to its lowest point in March and April (41 ± 0.7 g/kg^0.75). Mean retention time of hay, calculated from a chromium marker, declined (P<0.01) from 114 ± 4 h in March to 95 ± 4 h in July. Apparent organic matter digestibility decreased (P<0.01) from 74.7 ± 0.8% in winter to 61.7 ± 1.3% in summer. Compared with other ruminants, muskoxen are grazers exceptionally well-suited to slow, thorough digestion of graminoid forage. In the second study, the voluntary intake and apparent digestibility of a low-protein grass hay, similar in composition to diets of wild muskoxen in winter, were measured in five mature muskoxen and three mature Hereford cows during late winter 1993. Both species maintained body weight on the experimental diet but daily dry matter intake of the muskoxen was only 1/3 that of the cattle (32 ± 2 vs. 96 ± 3 g/kg^0.75; P<0.001). Apparent digestibility of organic matter, measured using chromic oxide, was higher in the muskoxen than in the cattle (58 ± 2 [SE] vs. 50 ± 3%; P=0.03). Muskoxen are particularly well adapted to digesting low quality graminoid forage at exceptionally low rates of intake. In the third study, the anatomical and chemical body composition of 22 muskoxen that varied widely in size, age and condition were analysed, and measures of body weight and condition were evaluated as predictors of body composition. The leanest muskoxen were four 5 to 15-day-old calves with 3.5 ± 0.5% (mean ± SE) fat in the IFBW, and the fattest were three females with 24.8 ± 1.4% fat. Muscle weight was best predicted from weights of individual muscles, protein weight from IFBW, bone weight from the weights of individual limb bones, and ash weight from IFBW. Combining kidney fat weight and a measure of body weight with up to three other measurements allowed dissectible and total fat weights to be estimated accurately. The extent of fattening in muskoxen exceeded that found in other wild ruminants with the exception of Svalbard reindeer (<i>Rangifer tarandus platyrhynchus</i>). In the fourth study, the body weight, body composition and reproductive status of 202 muskox cows from Victoria Island were analysed during 16 seasonal collections from 1989 to 1993. Adult muskox cows were lightest and leanest in May, when the ingesta-free body weight (IFBW) of newly-lactating adult cows was 116 ± 2 kg (adjusted mean ± SE) and a similar 112 ± 3 kg in nonlactating cows. Thereafter, the IFBW of lactating cows was virtually unchanged until July, increased rapidly during August, peaked in September at 166 ± 4 kg, then decreased to 148 ± 2 kg in November. In contrast, the IFBW of nonlactating cows increased throughout summer, reached a higher peak in September (176 ± 7 kg; P < 0.01) and changed little by November (164 + 2.1 kg). Pregnancy rates in this population increased from 0 in females 1.5 years old in the autumn to 25% in 2.5 year-olds and 62.5% in cows at least 3.5 years old. Lactation did not appear to peak until at least two months after calving, and was sometimes extended to more than a year. Lactation in November did not preclude pregnancy, but pregnant females at this time were fatter and heavier than nonpregnant cows. These results indicate substantial flexibility in reproductive patterns of muskoxen and an unique ability to maintain condition through long arctic winters. Based on these studies, the persistence of muskoxen through arctic winters can be ascribed in large part to exceptionally low maintenance requirements, along with an ability to thoroughly digest low-quality graminoid forage. Female muskoxen also deposit large quantities of fat in late summer and are able to conserve a large portion of them through early and mid- winter, and use them to support late-winter lactation. Muskox reproductive rates are strongly sensitive to nutritional influences. This suite of K-selected characters in muskoxen is consistent with a slow metabolism and a low rate of population growth.

O Maracanã- verdadeiro é um psitacídeo vulnerável a extinção, por estar havendo redução de suas populações em diferentes partes de sua área de ocorrência. Foi realizada uma revisão sobre a distribuição, histórica e atual, e o estatus da espécie através de dados de espécimes de museus e literatura. Foram reunidos 176 registros de localização do maracanã e comparadas as distribuições histórica e atual. Constatou-se, principalmente, uma contração dos limites ao sul da distribuição histórica da espécie. Dessa maneira, foi avaliado se nessa região a ocorrência do maracanã está associada a características da composição e estrutura da vegetação. Dados de ocorrência atual da espécie foram relacionados com a localização geográfica e índices de paisagem de 54 localidades, através da análise de regressão logística. Verificou-se que o “total de cobertura vegetal da paisagem" foi a única característica de paisagem significativamente relacionada com a ocorrência do maracanã (p<0,01), porém o poder explicativo da variável foi baixo. A variável “latitude" também foi altamente significativa (p<0,001) e não foi relacionada com nenhuma das métricas de paisagem analisadas. Isso sugere a existência de um outro fator não avaliado, com estrutura espacial em clina latitudinal, que está afetando as populações meridionais do maracanã. Foi também estudado o padrão de ocorrência do maracanã em escala local, no entorno da Estação Ecológica de Caetetus (2178 ha). Essa reserva está imersa em um mosaico de paisagem constituído por pequenos remanescentes florestais que podem ser importantes para a conservação da espécie. Foram amostradas 36 destas áreas remanescentes, através do método de contagens em pontos estratégicos. Cada fragmento obteve um índice de visitas por maracanã que foram relacionados as suas características espaciais, através da análise de regressão linear. As características das paisagens no entorno dos remanescentes estudados explicaram mais a variação da freqüência de visitas pelo maracanã que as características dos próprios fragmentos. As visitas dos maracanãs foram diretamente relacionadas com a “distância do fragmento até a cidade mais próxima" (p<0,05) e o “tamanho do remanescente" (p<0,05), e inversamente relacionado a “distância mínima do fragmento até um dormitório conhecido de maracanã" (p<0,01) e “distância mínima do fragmento até a E.E. dos Caetetus" (p<0,05). Todas essas análises indicaram que a conservação da paisagem como um todo parece ser fundamental para manutenção de populações do maracanã, em escala local e regional. Porém deve-se levar em conta a área dos fragmentos e sua configuração espacial, investindo esforços para a conservação das áreas de dormitórios. / The blue-winged macaw is a vulnerable psittacidae, which has been suffering a rapid reduction of its populations in different parts of its occurrence. Thus, it was carried a detailed revision on the, historical and current, distribution and estatus of the species through using literature and specimens in museums data. We gathered 176 records of blue-winged macaw sites and compared its historical and current distributions. We verified a range contraction in the south limit of blue-winged macaw’s historical occurence. In this way, we evaluated if, in this zone, the blue-winged macaw’s occurrence is correlated to composition and structure of residual vegetation. The current occurrence of the species was related to geographic coordinates and landscape indices of 54 localities, through the logistic regression analysis. The "total of vegetal cover of the landscape" was the only feature of the landscape significantly related to blue-winged macaw’s occurrence (p<0,01), however its explicatory power was very low. The "latitude" was highly significant to predict blue-winged macaw’s occurrence (p<0,001), and also was not related to any analyzed landscape metric. This suggests the existence of another non-evaluated factor, with spatial structure highly related to latitude, affecting the southern populations of blue-winged macaw. Also we studied the occurrence pattern of blue-winged macaw in local scale, around of Caetetus Ecological Station (2178 ha). This reserve is placed in a mosaic of landscape, consisting of small remnants of native vegetation that may have some value to the specie’s maintenance. We sampled 36 of these remaining areas through the method of countings in advantage points. Each remnant got a "blue-winged macaw’s visit index" that was related to spatial remnants features and its surrounding landscape, through the linear regression model. The landscape features around of the fragments explained more the variation of the bluewinged macaw’s visit index than the features of the fragments itself. The "index of visits of maracanãs" was directly related to "distance to the closest city" (p<0,05) and to "remnant size" (p<0,05), and inversely related to "distance to the closest known roost of blue winged macaw " (p<0,01) and "shortest distance to the Caetetus Ecological Station" (p<0,05). All these analyses indicate that the conservation of the landscape as a whole seems to be critical for the maintenance of blue-winged macaw’s populations, in local and regional scale. However the size of the remnants and its spatial configuration must be taken in account, besides the efforts for the conservation of the roost sites.

O Maracanã- verdadeiro é um psitacídeo vulnerável a extinção, por estar havendo redução de suas populações em diferentes partes de sua área de ocorrência. Foi realizada uma revisão sobre a distribuição, histórica e atual, e o estatus da espécie através de dados de espécimes de museus e literatura. Foram reunidos 176 registros de localização do maracanã e comparadas as distribuições histórica e atual. Constatou-se, principalmente, uma contração dos limites ao sul da distribuição histórica da espécie. Dessa maneira, foi avaliado se nessa região a ocorrência do maracanã está associada a características da composição e estrutura da vegetação. Dados de ocorrência atual da espécie foram relacionados com a localização geográfica e índices de paisagem de 54 localidades, através da análise de regressão logística. Verificou-se que o “total de cobertura vegetal da paisagem” foi a única característica de paisagem significativamente relacionada com a ocorrência do maracanã (p<0,01), porém o poder explicativo da variável foi baixo. A variável “latitude” também foi altamente significativa (p<0,001) e não foi relacionada com nenhuma das métricas de paisagem analisadas. Isso sugere a existência de um outro fator não avaliado, com estrutura espacial em clina latitudinal, que está afetando as populações meridionais do maracanã. Foi também estudado o padrão de ocorrência do maracanã em escala local, no entorno da Estação Ecológica de Caetetus (2178 ha). Essa reserva está imersa em um mosaico de paisagem constituído por pequenos remanescentes florestais que podem ser importantes para a conservação da espécie. Foram amostradas 36 destas áreas remanescentes, através do método de contagens em pontos estratégicos. Cada fragmento obteve um índice de visitas por maracanã que foram relacionados as suas características espaciais, através da análise de regressão linear. As características das paisagens no entorno dos remanescentes estudados explicaram mais a variação da freqüência de visitas pelo maracanã que as características dos próprios fragmentos. As visitas dos maracanãs foram diretamente relacionadas com a “distância do fragmento até a cidade mais próxima” (p<0,05) e o “tamanho do remanescente” (p<0,05), e inversamente relacionado a “distância mínima do fragmento até um dormitório conhecido de maracan㔠(p<0,01) e “distância mínima do fragmento até a E.E. dos Caetetus” (p<0,05). Todas essas análises indicaram que a conservação da paisagem como um todo parece ser fundamental para manutenção de populações do maracanã, em escala local e regional. Porém deve-se levar em conta a área dos fragmentos e sua configuração espacial, investindo esforços para a conservação das áreas de dormitórios. / The blue-winged macaw is a vulnerable psittacidae, which has been suffering a rapid reduction of its populations in different parts of its occurrence. Thus, it was carried a detailed revision on the, historical and current, distribution and estatus of the species through using literature and specimens in museums data. We gathered 176 records of blue-winged macaw sites and compared its historical and current distributions. We verified a range contraction in the south limit of blue-winged macaw’s historical occurence. In this way, we evaluated if, in this zone, the blue-winged macaw’s occurrence is correlated to composition and structure of residual vegetation. The current occurrence of the species was related to geographic coordinates and landscape indices of 54 localities, through the logistic regression analysis. The "total of vegetal cover of the landscape" was the only feature of the landscape significantly related to blue-winged macaw’s occurrence (p<0,01), however its explicatory power was very low. The "latitude" was highly significant to predict blue-winged macaw’s occurrence (p<0,001), and also was not related to any analyzed landscape metric. This suggests the existence of another non-evaluated factor, with spatial structure highly related to latitude, affecting the southern populations of blue-winged macaw. Also we studied the occurrence pattern of blue-winged macaw in local scale, around of Caetetus Ecological Station (2178 ha). This reserve is placed in a mosaic of landscape, consisting of small remnants of native vegetation that may have some value to the specie’s maintenance. We sampled 36 of these remaining areas through the method of countings in advantage points. Each remnant got a "blue-winged macaw’s visit index" that was related to spatial remnants features and its surrounding landscape, through the linear regression model. The landscape features around of the fragments explained more the variation of the bluewinged macaw’s visit index than the features of the fragments itself. The "index of visits of maracanãs" was directly related to "distance to the closest city" (p<0,05) and to "remnant size" (p<0,05), and inversely related to "distance to the closest known roost of blue winged macaw " (p<0,01) and "shortest distance to the Caetetus Ecological Station" (p<0,05). All these analyses indicate that the conservation of the landscape as a whole seems to be critical for the maintenance of blue-winged macaw’s populations, in local and regional scale. However the size of the remnants and its spatial configuration must be taken in account, besides the efforts for the conservation of the roost sites.

No description available.

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