Observation of Adoption in Polar Bears (Ursus maritimus)

We observed a case of adoption of a single four-month-old polar bear cub (Ursus maritimus) into an existing litter of two cubs on Hopen Island, Svalbard. We believe the high density of maternity dens in the study area may increase the likelihood of natural adoption. Speculation about theoretical implications of adoption is of scientific interest. However, we believe that the probability of adoption may increase when family groups are captured, and the scientific interpretation of such events is of questionable value. We urge researchers to exercise caution in handling family groups in high-density den areas.Dans l'île Hopen au Svalbard, on a observé le cas d'adoption d'un ourson polaire (Ursus maritimus) unique âgé de quatre mois au sein d'une portée de deux oursons. On pense que la forte densité de tanières de mise bas dans la zone d'étude pourrait accroître la probabilité de l'adoption naturelle. Les hypothèses concernant les implications théoriques de l'adoption relèvent d'un intérêt scientifique. Nous croyons cependant que la probabilité de l'adoption peut augmenter quand les groupes familiaux sont capturés, et on peut se poser des questions quant à l'interprétation scientifique de telles manifestations. Nous recommandons fortement aux chercheurs de prendre des précautions lors de la manipulation de groupes familiaux dans des aires de mise bas à forte densité

Infanticide and Cannibalism of Juvenile Polar Bears (Ursus maritimus) in Svalbard

Two instances of infanticide and cannibalism in polar bears (Ursus maritimus) were observed in SE Svalbard, at Hopen Island. In the first, an adult male killed three young cubs at a den site and consumed one of them. In the second, an adult male actively pursued, killed, and consumed a dependent yearling. Infanticide of dependent polar bear offspring by adult males may be more common in Svalbard than in other populations because the population is close to carrying capacity or because geographic features reduce spatial segregation of age and sex classes.On a observé deux cas d'infanticide et de cannibalisme chez l'ours polaire (Ursus maritimus) à l'île Hopen, dans le sud-est du Svalbard. Dans le premier cas, un mâle adulte a tué trois oursons dans leur tanière et en a dévoré un. Dans le second, un mâle adulte a pourchassé, tué et dévoré un ourson d'un an non autonome. Il se peut que, chez l'ours polaire, l'infanticide des petits non autonomes par des mâles adultes soit plus commun au Svalbard que dans d'autres populations en raison de la taille de la population qui est proche de la capacité biogénique ou parce que les caractéristiques géographiques réduisent la ségrégation spatiale des catégories d'âges et de sexes

Possible Impacts of Climatic Warming on Polar Bears

If climatic warming occurs, the first impacts on polar bears (Ursus maritirnus) will be felt at the southern limits of their distribution, such as in James and Hudson bays, where the whole population is already forced to fast for approximately four months when the sea ice melts during the summer. Prolonging the ice-free period will increase nutritional stress on this population until they are no longer able tost ore enough fat to survive thicee -free period. Early signs of impact will include declining body condition, lowered reproductive rates, reduced survival of cubs, and an increase in polar bear-human interactions. Although most of these changes are currently detectable in the polar bears of western Hudson Bay, it cannot yet be determined if climatic change is involved. In the High Arctic, a decrease in ice cover may stimulate an initial increase in biological productivity. Eventually however, it is likely that seal populations will decline wherever the quality and availability of breeding habitat are reduced. Rain during the late winter may cause polar bear maternity dens to collapse, causing the death of occupants. Human-bear problems will increase as the open water period becomes longer and bears fasting and relyingo n their fat reserves become foods tressed. If populations opf olar bears decline, harvest quotas for native people will be reduced and eventually be eliminatedT. ourism based on viewingp olar bears in western HudsonB ay will likely disappear. Should theA rctic Ocean become seasonally ice free for a long enough period, it is likely polar bears would become extirpated from at least the southern part of their range. If climatic warming occurs, the polar bear is an ideal species through which to monitor the cumulative effects in arctic marine ecosystems because of its position at the top of the arctic marine food chain

Infanticide and cannibalism of juvenile polar bears (Ursus maritimus) in Svalbard

Two instances of infanticide and cannibalism in polar bears (Ursus maritimus) were observed in SE Svalbard, at Hopen Island. In the first, an adult male killed three young cubs at a den site and consumed one of them. In the second, an adult male actively pursued, killed, and consumed a dependent yearling. Infanticide of dependent polar bear offspring by adult males may be more common in Svalbard than in other populations because the population is close to carrying capacity or because geographic features reduce spatial segregation of age and sex classes

Adoption in Polar Bears (Ursus maritimus)

We observed a case of adoption of a single four-month-old polar bear cub (Ursus maritimus) into an existing litter of two cubs on Hopen Island, Svalbard. We believe the high density of maternity dens in the study area may increase the likelihood of natural adoption. Speculation about theoretical implications of adoption is of scientific interest. However, we believe that the probability of adoption may increase when family groups are captured, and the scientific interpretation of such events is of questionable value. We urge researchers to exercise caution in handling family groups in high-density den areas

Estimating Allee thresholds before they can be observed: polar bears as a case study.

Allee effects are an important component in the population dynamics of numerous species. Accounting for these Allee effects in population viability analyses generally requires estimates of low-density population growth rates, but such data are unavailable for most species and particularly difficult to obtain for large mammals. Here, we present a mechanistic modeling framework that allows estimating the expected low-density growth rates under a mate-finding Allee effect before the Allee effect occurs or can be observed. The approach relies on representing the mechanisms causing the Allee effect in a process-based model, which can be parameterized and validated from data on the mechanisms rather than data on population growth. We illustrate the approach using polar bears (Ursus maritimus), and estimate their expected low-density growth by linking a mating dynamics model to a matrix projection model. The Allee threshold, defined as the population density below which growth becomes negative, is shown to depend on age-structure, sex ratio, and the life history parameters determining reproduction and survival. The Allee threshold is thus both density- and frequency-dependent. Sensitivity analyses of the Allee threshold show that different combinations of the parameters determining reproduction and survival can lead to differing Allee thresholds, even if these differing combinations imply the same stable-stage population growth rate. The approach further shows how mate-limitation can induce long transient dynamics, even in populations that eventually grow to carrying capacity. Applying the models to the overharvested low-density polar bear population of Viscount Melville Sound, Canada, shows that a mate-finding Allee effect is a plausible mechanism for slow recovery of this population. Our approach is generalizable to any mating system and life cycle, and could aid proactive management and conservation strategies, for example, by providing a priori estimates of minimum conservation targets for rare species or minimum eradication targets for pests and invasive species

Conservation and management of Canada’s polar bears (<i>Ursus maritimus</i>) in a changing Arctic¹This review is part of the virtual symposium “Flagship Species – Flagship Problems” that deals with ecology, biodiversity and management issues, and climate impacts on species at risk and of Canadian importance, including the polar bear (<i>Ursus maritimus</i>), Atlantic cod (<i>Gadus morhua</i>), Piping Plover (<i>Charadrius melodus</i>), and caribou (<i>Rangifer tarandus</i>).

Canada has an important responsibility for the research, conservation, and management of polar bears ( Ursus maritimus Phipps, 1774) because the majority of polar bears in the world occur within the nation’s borders. Two fundamental and recent changes for polar bears and their conservation have arisen: (1) the ongoing and projected further decline of sea-ice habitat as a result of climate change and (2) the implementation of aboriginal land claims and treaties in Canada’s North. Science has documented empirical links between productivity of polar bear population and sea-ice change. Predictive modeling based on these data has forecast significant declines in polar bear abundance and distribution of polar bears. With the signing of northern land claims and treaties, polar bear management in Canada has integrated local aboriginal participation, values, and knowledge. The interaction of scientific and local perspectives on polar bears as they relate to harvest, climate change, and declining habitat has recently caused controversy. Some conservation, management, and research decisions have been contentious because of gaps in scientific knowledge and the polarization and politicization of the roles of the various stakeholders. With these ecological and governance transitions, there is a need to re-focus and re-direct polar bear conservation in Canada. </jats:p

Identification of HSP70 homologues in chloroplasts.

Cytoplasmic members of the heat shock protein hsp70 family have recently been implicated in the transport of proteins to the endoplasmic reticulum and mitochondria. In addition, other hsp70 homologues have been found in the endoplasmic reticulum and mitochondria and, at least for the endoplasmic reticulum hsp70 homologue, may be involved in the proper folding and assembly of newly transported proteins. Since chloroplasts are an important site of protein transport in plant cells, we were interested in determining whetherhsp70 proteins might be located in this organelle. By using immune-blotting techniques and two antibody separations against hsp70 proteins, we have identified three chloroplast icproteins of approximately 70k Dathatae related to hsp70 proteins. One of these proteins was tightly associated with the outer envelope membrane and was not exposed at the outer surface of the chloroplasts. The other two were soluble proteins located in the stroma. Steady-state levels of the chloroplastic hsp70 homologues did not change after heat stress nor were any additional hsp70 homologues detected in chloroplasts isolated from heat- stressed plants. We discuss the possible functions of these hsp7O homologues in the transport of proteins into and within chloroplasts