Genetic Relationships of Extant Brown Bears (Ursus arctos) and Polar Bears (Ursus maritimus)

Since the late 1700s, reports of polar bears (Ursus maritimus) using tools (i.e., pieces of ice or stones) to kill walruses (Odobenus rosmarus) have been passed on verbally to explorers and naturalists by their Inuit guides, based on local traditional ecological knowledge (TEK) as well as accounts of direct observations or interpretations of tracks in the snow made by the Inuit hunters who reported them. To assess the possibility that polar bears may occasionally use tools to hunt walruses in the wild, we summarize 1) observations described to early explorers and naturalists by Inuit hunters about polar bears using tools, 2) more recent documentation in the literature from Inuit hunters and scientists, and 3) recent observations of a polar bear in a zoo spontaneously using tools to access a novel food source. These observations and previously published experiments on brown bears (Ursus arctos) confirm that, in captivity, polar and brown bears are both capable of conceptualizing the use of a tool to obtain a food source that would otherwise not be accessible. Based on the information from all our sources, this may occasionally also have been the case in the wild. We suggest that possible tool use by polar bears in the wild is infrequent and mainly limited to hunting walruses because of their large size, difficulty to kill, and their possession of potentially lethal weapons for both their own defense and the direct attack of a predator.

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New insights into dietary management of polar bears ( Ursus maritimus ) and brown bears ( U. arctos )

Zoo Biology ◽

10.1002/zoo.21658 ◽

2021 ◽

Author(s):

Charles T. Robbins ◽

Troy N. Tollefson ◽

Karyn D. Rode ◽

Joy A. Erlenbach ◽

Amanda J. Ardente

Keyword(s):

Ursus Maritimus ◽

Dietary Management ◽

Polar Bears ◽

Brown Bears

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A phenological comparison of grizzly (Ursus arctos) and polar bears (Ursus maritimus) as waterfowl nest predators in Wapusk National Park

Polar Biology ◽

10.1007/s00300-020-02647-w ◽

2020 ◽

Vol 43 (5) ◽

pp. 457-465

Author(s):

Andrew F. Barnas ◽

David T. Iles ◽

Tanner J. Stechmann ◽

Erin M. Wampole ◽

David N. Koons ◽

...

Keyword(s):

National Park ◽

Ursus Arctos ◽

Ursus Maritimus ◽

Polar Bears ◽

Nest Predators

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Trichinella and polar bears: a limited risk for humans

Journal of Helminthology ◽

10.1017/s0022149x17000219 ◽

2017 ◽

Vol 91 (4) ◽

pp. 440-446 ◽

Cited By ~ 4

Author(s):

J. Dupouy-Camet ◽

P. Bourée ◽

H. Yera

Keyword(s):

World War Ii ◽

Polar Bear ◽

Ursus Maritimus ◽

The Arctic ◽

Polar Bears ◽

World War ◽

Protected Species ◽

Brown Bears ◽

Limited Access ◽

Human Trichinellosis

AbstractIn this review, we identified 63 cases reported since World War II of human trichinellosis linked to the consumption of parasitized polar bear (Ursus maritimus) meat. This low number contrasts to the numerous cases of human trichinellosis related to consumption of the meat of black (U. americanus) or brown bears (U. arctos). The prevalence of Trichinella infection is high in bears, but larval muscular burden is usually lower in polar bears compared to other bear species. Polar bears, therefore, seem to play a limited role in the transmission of trichinellosis to humans, as native residents living in the Arctic traditionally consume well-cooked bear meat, and travellers and foreign hunters have only limited access to this protected species due to the declining polar bear population.

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Interspecific and intraspecific mitochondrial DNA variation in North American bears (Ursus)

Canadian Journal of Zoology ◽

10.1139/z91-421 ◽

1991 ◽

Vol 69 (12) ◽

pp. 2985-2992 ◽

Cited By ~ 60

Author(s):

Matthew A. Cronin ◽

Steven C. Amstrup ◽

Gerald W. Garner ◽

Ernest R. Vyse

Keyword(s):

Mitochondrial Dna ◽

North American ◽

Ursus Arctos ◽

Phylogenetic Analyses ◽

Sequence Divergence ◽

Black Bears ◽

Polar Bears ◽

Brown Bears ◽

Dna Variation ◽

Base Substitutions

We assessed mitochondrial DNA variation in North American black bears (Ursus americanus), brown bears (Ursus arctos), and polar bears (Ursus maritimus). Divergent mitochondrial DNA haplotypes (0.05 base substitutions per nucleotide) were identified in populations of black bears from Montana and Oregon. In contrast, very similar haplotypes occur in black bears across North America. This discordance of haplotype phylogeny and geographic distribution indicates that there has been maintenance of polymorphism and considerable gene flow throughout the history of the species. Intraspecific mitochondrial DNA sequence divergence in brown bears and polar bears is lower than in black bears. The two morphological forms of U. arctos, grizzly and coastal brown bears, are not in distinct mtDNA lineages. Interspecific comparisons indicate that brown bears and polar bears share similar mitochondrial DNA (0.023 base substitutions per nucleotide) which is quite divergent (0.078 base substitutions per nucleotide) from that of black bears. High mitochondrial DNA divergence within black bears and paraphyletic relationships of brown and polar bear mitochondrial DNA indicate that intraspecific variation across species' ranges should be considered in phylogenetic analyses of mitochondrial DNA.

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Sarcocystis arctosi sp. nov. (Apicomplexa, Sarcocystidae) from the brown bear (Ursus arctos), and its genetic similarity to schizonts of Sarcocystis canis-like parasite associated with fatal hepatitis in polar bears (Ursus maritimus)

Acta Parasitologica ◽

10.2478/s11686-007-0048-6 ◽

2007 ◽

Vol 52 (4) ◽

Cited By ~ 8

Author(s):

J. Dubey ◽

Benjamin Rosenthal ◽

Natarajan Sundar ◽

G. Velmurugan ◽

Kimberlee Beckmen

Keyword(s):

Ursus Arctos ◽

Brown Bear ◽

Ursus Maritimus ◽

Small Subunit ◽

Vacuolar Membrane ◽

Ground Substance ◽

Polar Bears ◽

Thin Walls ◽

Small Subunit Rdna ◽

A New Species

AbstractThe tissues of herbivores are commonly infected with cysts of parasites belonging to the apicomplexan genus Sarcocystis, but such sarcocysts are rare in bears. Here, we describe a new species, Sarcocystis arctosi, based on the mature sarcocysts identified in two brown bears (Ursus arctos) from Alaska, USA. Microscopic sarcocysts (37–75 × 20–42 μm) had thin walls (<1 μm). The outer layer of the sarcocyst, the parasitophorous vacuolar membrane (pvm), was wavy in outline and had minute undulations that did not invaginate towards the sarcocyst interior; these undulations occurred at irregular intervals and measured up to 100 nm in length and up to 60 nm width. The ground substance layer beneath the pvm was smooth and lacked microtubules. Longitudinally cut bradyzoites measured 5.6–6.8 × 0.7–1.8 μm. A major portion of nuclear small subunit rDNA sequence obtained from these sarcocysts was similar to that previously obtained from the hepatic schizonts of a S. canis-like parasite from polar bears (Ursus maritimus).

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Genetic relationships of North American bears (Ursus) inferred from amplified fragment length polymorphisms and mitochondrial DNA sequences

Canadian Journal of Zoology ◽

10.1139/cjz-2013-0078 ◽

2013 ◽

Vol 91 (9) ◽

pp. 626-634 ◽

Cited By ~ 12

Author(s):

M.A. Cronin ◽

M.M. McDonough ◽

H.M. Huynh ◽

R.J. Baker

Keyword(s):

Mitochondrial Dna ◽

Fragment Length ◽

Genetic Relationships ◽

Black Bears ◽

Gene Pools ◽

Polar Bears ◽

Brown Bears ◽

Southeast Alaska ◽

Length Polymorphisms ◽

Amplified Fragment Length Polymorphisms

The three species of bears in North America, polar bears (Ursus maritimus Phipps, 1774), brown bears (Ursus arctos L., 1758), and black bears (Ursus americanus Pallas, 1780), have differentiated morphologies and nuclear and mitochondrial genomes. An exception is a paraphyletic mitochondrial DNA relationship and some nuclear gene lineages common to polar bears and a population of brown bears from islands in southeast Alaska. In this study, we quantified the genetic relationships of extant brown bears and black bears from Alaska and Montana, and polar bears from Alaska, with amplified fragment length polymorphisms (AFLP) and mtDNA cytochrome-b sequences. Bayesian cluster analyses of the AFLP data show each species is distinct. All brown bears, including those from the islands in southeast Alaska, cluster separately from polar bears, and black bears cluster separately from brown bears and polar bears. The mtDNA of polar bears and southeast Alaska island brown bears is paraphyletic as reported previously, but the species have different haplotypes. These data indicate that extant populations of brown bears and polar bears have separate nuclear and mitochondrial gene pools and are supported as species under the genetic species concept.

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Molecular Phylogeny and SNP Variation of Polar Bears (Ursus maritimus), Brown Bears (U. arctos), and Black Bears (U. americanus) Derived from Genome Sequences

Journal of Heredity ◽

10.1093/jhered/est133 ◽

2014 ◽

Vol 105 (3) ◽

pp. 312-323 ◽

Cited By ~ 14

Author(s):

Matthew A. Cronin ◽

Gonzalo Rincon ◽

Robert W. Meredith ◽

Michael D. MacNeil ◽

Alma Islas-Trejo ◽

...

Keyword(s):

Molecular Phylogeny ◽

Ursus Maritimus ◽

Black Bears ◽

Polar Bears ◽

Genome Sequences ◽

Brown Bears

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Insights into bear evolution from a Pleistocene polar bear genome

10.1101/2021.12.11.472228 ◽

2021 ◽

Author(s):

Tianying Lan ◽

Kalle Leppala ◽

Crystal Tomlin ◽

Sandra L Talbot ◽

George K Sage ◽

...

Keyword(s):

Climate Change ◽

Polar Bear ◽

Ursus Arctos ◽

Genetic Erosion ◽

Brown Bear ◽

Population History ◽

Polar Bears ◽

Effective Population ◽

Brown Bears ◽

Svalbard Archipelago

The polar bear (Ursus maritimus) has become a symbol of the threat to biodiversity from climate change. Understanding polar bear evolutionary history may provide insights into apex carnivore responses and prospects during periods of extreme environmental perturbations. In recent years, genomic studies have examined bear speciation and population history, including evidence for ancient admixture between polar bears and brown bears (Ursus arctos). Here, we extend our earlier studies of a 130,000-115,000-year-old polar bear from the Svalbard Archipelago using 10X coverage genome sequence and ten new genomes of polar and brown bears from contemporary zones of overlap in northern Alaska. We demonstrate a dramatic decline in effective population size for this ancient polar bear's lineage, followed by a modest increase just before its demise. A slightly higher genetic diversity in the ancient polar bear suggests a severe genetic erosion over a prolonged bottleneck in modern polar bears. Statistical fitting of data to alternative admixture graph scenarios favors at least one ancient introgression event from brown bears into the ancestor of polar bears, possibly dating back over 150,000 years. Gene flow was likely bidirectional, but allelic transfer from brown into polar bear is the strongest detected signal, which contrasts with other published works. These findings have implications for our understanding of climate change impacts: polar bears, a specialist Arctic lineage, may not only have undergone severe genetic bottlenecks, but also been the recipient of generalist, boreal genetic variants from brown bear during critical phases of Northern Hemisphere glacial oscillations.

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Genomic evidence of globally widespread admixture from polar bears into brown bears during the last ice age

10.1101/154773 ◽

2017 ◽

Author(s):

James A. Cahill ◽

Peter D. Heintzman ◽

Kelley Harris ◽

Matthew Teasdale ◽

Joshua Kapp ◽

...

Keyword(s):

Climate Change ◽

Polar Bear ◽

Ursus Arctos ◽

Brown Bear ◽

Ice Age ◽

Evolutionary Significance ◽

Polar Bears ◽

Brown Bears ◽

Last Ice Age ◽

Genomic Introgression

AbstractRecent genomic analyses have provided substantial evidence for past periods of gene flow from polar bears (Ursus maritimus) into Alaskan brown bears (Ursus arctos), with some analyses suggesting a link between climate change and genomic introgression. However, because it has only been possible to sample bears from the present day, the timing, frequency, and evolutionary significance of this admixture remains unknown. Here, we analyze genomic DNA from three additional and geographically distinct brown bear populations, including two that lived temporally close to the peak of the last ice age. We find evidence of admixture in all three populations, suggesting that admixture between these species has been common in their recent evolutionary history. In addition, analyses of ten fossil bears from the now-extinct Irish population indicate that admixture peaked during the last ice age, when brown bear and polar bear ranges overlapped. Following this peak, the proportion of polar bear ancestry in Irish brown bears declined rapidly until their extinction. Our results support a model in which ice age climate change created geographically widespread conditions conducive to admixture between polar bears and brown bears, as is again occurring today. We postulate that this model will be informative for many admixing species pairs impacted by climate change. Our results highlight the power of paleogenomes to reveal patterns of evolutionary change that are otherwise masked with only contemporary data.

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