Ursidae in der Sammlung von Koenigswald.
Diplomarbeit, Fachbereich Biologie der Johann Wolfgang Goethe-Universität Frankfurt
Um zu verstehen, warum die verschiedenen Bärenarten so sind wie sie sind muss man 2 Punkte beachten:
1. Sie entwickelten sich aus Carnivoren und entwickelten herbivore Adaptionen aus einer carnivoren Form heraus.
2. sie haben sich erst “kürzlich” entwickelt und mussten sich Nischen suchen, die nicht schon von anderen, älteren Carnivoren besetzt waren.
Die Großkatzen, wie Löwen und Tiger waren schon soweit entwickelt, dass sie auf größere Beute spezialisiert waren. Die Canidae waren auf kleinere und mittelgroße Beute spezialisiert. Als sich die Bären entwickelten, mussten sie sich auf die noch nicht genutzte Nahrung spezialisieren. So entwickelte sich der Lippenbär im Indischen Subkontinent. Dort hatten sich bereits Löwen, Tiger und Leoparden gut etabliert. Früchte war en nur saisonal als Nahrung zu gebrauchen und konnten nicht das ganze Jahr als Nahrungsquelle dienen. Insekten, jedoch, wie Ameisen und Termiten hatten einen hohen Kalorienanteil, waren immer da und wurden noch nicht von anderen Tieren als Nahrungsquelle genutzt. Im Laufe der Zeit entwickelten die Vorfahren des Lippenbären Adaptionen, wie beweglichen Lippen und den Verlust der oberen Incisivi, so dass die Insekten als verlässliche ganzjährige Nahrung dienen konnten. Malaienbären wurden ausgezeichnete Kletterer und ernähren sich hauptsächlich von Früchten und Honig. Pandas nutzten die große Menge an Bambus aus. Obwohl sie sich streng herbivor ernähren, behalten sie weiterhin die Eckzähne und Schneidezähne ihrer Vorfahren.
Polar Bears: The Natural History of a Threatened Species.
Markham, Ontario, Canada: Fitzhenry & Whiteside, 334 pp. ISBN 978-1-55455-155-2.
The book covers polar bear population ecology, behaviour, physiology, genetics, interspecic relationships with seals, sea ice, polynyas, denning habitat, environmental degradation, human development, and models of future Arctic change. It is largely non-technical, providing a broad understanding of the ecology and natural history of polar bears that is accessible to most people. Yet it does not “talk down” to readers; they can expect to be challenged with complex ideas and difcult topics, from the effects of contaminants on polar bears (e.g., hermaphroditism) to models of predicted climate change. Some of the best writing is found in Ian’s descriptions of how polar bears travel, hunt, eat, den, and interact. His many hours in the eld have provided him with a unique perspective that can give readers a sense of what it is like to be a polar bear.
Most of the book is scientic in presentation, but the stories of unique observations made by Stirling and his
colleagues are equally interesting and valuable.
Polar Bears and Seals in the Eastern Beaufort Sea and Amundsen Gulf:
A Synthesis of Population Trends and Ecological Relationships over Three Decades.
ARCTIC, Vol. 55, SUPP. 1: 59-76.
In the eastern Beaufort Sea and Amundsen Gulf, research on polar bear populations and their ecological interrelationships with seals and sea ice conditions began in the fall of 1970. Analysis of movement data from mark-recapture studies and tracking of adult female bears with satellite radio collars indicated that there are two populations of polar bears in the area, one that inhabits the west coast of Banks Island and Amundsen Gulf and a second that is resident along the mainland coast from about Baillie Islands in Canada to approximately Icy Cape in Alaska. Polar bears throughout the Beaufort Sea and Amundsen Gulf were severely overharvested before the establishment of quotas in Canada in 1968 and the cessation of all but subsistence polar bear hunting in Alaska in 1972. Since then, both populations have recovered, and the population estimates currently used for management purposes are 1200 and 1800 for the Northern and Southern Beaufort populations, respectively. However, these population estimates are now dated and should be redone. Most female polar bears in the Beaufort Sea breed for the first time at 5 years of age, compared to 4 years of age in most other populations, and cubs normally remain with their mothers for 2.5 years prior to weaning. Heavy ice conditions in the mid-1970s and mid-1980s caused significant declines in productivity of ringed seals, each of which lasted about 3 years and caused similar declines in the natality of polar bears and survival of subadults, after which reproductive success and survival of both species increased again. The changes in the sea ice environment, and their consequent effects on polar bears, are demonstrable in parallel fluctuations in the mean ages of polar bears killed each year by Inuit hunters. In 1989, the decadal-scale pattern in fluctuations of ice conditions in the eastern Beaufort Sea changed in response to oceanographic and climatic factors, and this change has resulted in greater amounts of open water in recent years. In addition, climatic warming will be a major environmental factor if greenhouse gas emissions continue to increase. It is unknown whether the ecosystem will return to the pattern of decadal-scale change exhibited in previous decades, or how polar bears and seals will respond to ecological changes in the future, but research on these topics is a high priority.
Familienzusammenführung bei den Eisbären des Kölner Zoos - ein Ausnahmefall.
Z. Kölner Zoo 38 (3): 113-121.
Reproductive biology and ecology of female polar bears (Ursus maritimus).
J. Zool. Lond., 214: 601-634.
Data on age‐specific natality rates, litter size, interbirth interval, age of first reproduction, reproductive senescence, age of weaning and cub survival were determined for a free‐ranging population of polar bears inhabiting Hudson Bay, Canada, near the southern limit of the species range. Serum progesterone levels were also determined for females at different stages of their reproductive cycle to provide corroborative support for the reproductive parameters described. Animals were live captured using immobilizing drugs and each animal uniquely marked for future identification. First parturition occurred at four or five years of age and the age‐specific natality rate increased with age until approximately 20 years, after which it dropped markedly. At least 40% of adult females displayed two‐year interbirth intervals and 55% of cubs in their second year were independent of their mother. Mean size of cub litters in spring was 1.9 and 13% of litters had three or more cubs. The natality rate for 5–20‐year‐old females was estimated as 0.9, higher than that reported for any more northerly polar bear populations where two‐year interbirth intervals are rare, fewer than 5% of yearling cubs are weaned and triplet litters occur with less than 1% frequency. Cub mortality was initially high and declined with age. Although cubs in western Hudson Bay were weaned at a younger age and a lighter weight than their counterparts in more northern populations, cub mortality rates were similar. The reason for the marked differences in reproductive parameters in the western Hudson Bay population is not known. We speculate that sea‐ice conditions may be sufficiently different to allow weaned bears at a lighter body weight to hunt seals more successfully there than further north.
Zucht und Aufzucht von Eisbären (Ursus maritimus) - ein Diskussionsbeitrag.
In: LINKE, K. (2008) International Studbook for Polar Bears, Ursus maritimus, 2006-2007. Zoo Rostock: 15-23
Aspects of survival in juvenile polar bears.
Can. J. Zool, 74:1246-1252.
We captured, weighed, tagged, and monitored polar bear (Ursus maritimus) cubs and yearlings in western Hudson Bay to examine survival rates and correlates with survival. Cub survival between spring and autumn increased with cub mass and maternal mass, but was not related to maternal age or maternal condition. Cub survival between spring and autumn varied annually between 39.0 and 100.0% and averaged 53.2%. Whole-litter loss between spring and autumn was 30.8%, and only 38.0% of the females did not lose any cubs. Survival of spring twins was similar regardless of size, but in triplet litters, survival between spring and autumn varied according to cub size. Minimum cub survival from one autumn to the next was 34.7% and was related to cub mass, maternal mass, and maternal condition. Cub survival during autumn was estimated at 83.0%. Survival during the first year of life was no more than 44.0% but we could not estimate an annual survival rate because of the sampling regime. Possibly because harvesting was the major mortality factor for yearlings (19.4% of the yearlings were removed from the population per year), no factors examined correlated with survival of yearlings. We found no sex-related differences in survival of cubs or yearlings in any period. Relationships between survival in polar bear cubs and their condition suggest that lack of food availability, sometimes due to low maternal fat stores for lactation, leads to starvation and may be the main cause of mortality.
Aspects of survival in juvenile polar bears (PDF Download Available). Available from: https://www.researchgate.net/publication/238037133_Aspects_of_survival_in_juvenile_polar_bears [accessed Jun 21 2018].