Ursus (mammal)

Ursus; Temporal range: Pliocene–Holocene, 5.333–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	From top to bottom: brown bear, American black bear, polar bear, Asian black bear
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Family:	Ursidae
Subfamily:	Ursinae
Tribe:	Ursini
Genus:	Ursus ; Linnaeus, 1758
Type species
	Ursus arctos ; Linnaeus, 1758
Species
	Ursus arctos ; Ursus americanus ; Ursus maritimus ; Ursus thibetanus ; † Ursus spelaeus ;
Synonyms
	ArcticonusPocock, 1917; DanisJ. E. Gray, 1825; EuarctosGray, 1864; MamursusHerrara, 1899; MelanarctosHeude, 1898; MylarctosLonney, 1923; MyrmarctosGray, 1864; SelenarctosHeude, 1901; SpelearctosGeoffrey, 1833; ThalassarctosJ. E. Gray, 1825; ThalassiarchusKobolt, 1896; UrsarctosHeude, 1898; UrsulusKretzoi, 1954; VetularctosMerriam, 1918;

Last updated July 26, 2024

Ursus is a genus in the family Ursidae (bears) that includes the widely distributed brown bear,^[3] the polar bear,^[4] the American black bear, and the Asian black bear. The name is derived from the Latin ursus, meaning bear.^[5]^[6]

Taxonomy and systematics

Extant species

Genus **Ursus** – Linnaeus, 1758 – four species
Common name	Scientific name and subspecies	Range	Size and ecology	IUCN status and estimated population
American black bear	Ursus americanus Pallas, 1780 16 subspecies U. a. altifrontalis – Olympic black bear U. a. amblyceps – New Mexico black bear U. a. americanus – Eastern black bear U. a. californiensis – California black bear U. a. carlottae – Haida Gwaii black bear or Queen Charlotte Islands black bear U. a. cinnamomum – cinnamon bear U. a. emmonsii – glacier bear U. a. eremicus – East Mexican black bear^[7] U. a. floridanus – Florida black bear U. a. hamiltoni – Newfoundland black bear U. a. kermodei – Kermode bear or spirit bear U. a. luteolus – Louisiana black bear U. a. machetes – West Mexican black bear^[8] U. a. perniger – Kenai black bear U. a. pugnax – Dall Island black bear U. a. vancouveri – Vancouver Island black bear	American Southwest and Mexico	Size: Habitat: Diet:	LC
Brown bear	Ursus arctos Linnaeus, 1758 15 subspecies U. a. arctos – Eurasian brown bear U. a. collaris – East Siberian brown bear U. a. beringianus – Kamchatkan brown bear †U. a. californicus - California grizzly bear (extinct) †U. a. crowtheri – Atlas bear (extinct) †U. a. dalli – Dall Island brown bear^[9] (extinct) U. a. gyas - Alaska Peninsula brown bear U. a. horribilis – grizzly bear U. a. isabellinus – Himalayan brown bear U. a. lasiotus – Ussuri brown bear U. a. middendorffi – Kodiak bear †U. a. nelsoni – Mexican grizzly bear (extinct) U. a. pruinosus – Tibetan blue bear U. a. sitkensis – Sitka brown bear U. a. stikeenensis - Stikine brown bear U. a. syriacus – Syrian brown bear	Russia, Central Asia, China, Canada, the United States (mostly Alaska), Scandinavia, and the Carpathian region (especially Romania), Anatolia, and Caucasus	Size: Habitat: Diet:	LC
Polar bear	Ursus maritimus Phipps, 1774 2 subspecies U. m. maritimus modern polar bear † U. m. tyrannus Pleistocene polar bear (possibly a brown bear)	Arctic Circle and adjacent land masses as far south as Newfoundland.	Size: Habitat: Diet:	VU
Asian black bear	Ursus thibetanus G. Cuvier, 1823 7 subspecies U. t. formosanus - Formosan black bear, U. t. gedrosianus – Balochistan black bear or Pakistan black bear U. t. japonicus – Japanese black bear U. t. laniger – Himalayan black bear U. t. mupinensis – Indochinese black bear U. t. thibetanus – Tibetan black bear U. t. ussuricus – Ussuri black bear	Indian subcontinent, Korea, northeastern China, the Russian Far East, the Honshū and Shikoku islands of Japan, and Taiwan	Size: Habitat: Diet:	VU

A hybrid between grizzly bears and polar bears has also been recorded. Known commonly as a pizzly, prizzly, or grolar bear, the official name is simply "grizzly–polar bear hybrid".

Fossils

† Ursus deningeri Richenau, 1904
† Ursus dolinensis (Garcia & Arsuaga, 2001)
† Ursus etruscus Cuvier, 1823
† Ursus ingressus Rabeder, Hofreiter, Nagel & Withalm 2004
† Ursus kudarensis Baryshnikov, 1985
† Ursus minimus (Devèze & Bouillet, 1827)
† Ursus pyrenaicus (Depéret, 1892)
† Ursus rossicus Borissiak, 1930
† Ursus savini (Andrews, 1922)
† Ursus sackdillingensis Heller, 1955
† Ursus spelaeus Rosenmüller, 1794
† Ursus vitabilis ? Gidley, 1913

Mating system ecology

The mating systems within the genus Ursus are primarily classified as polygynous, polyandrous and promiscuous.^[10] Both males and females mate with more than one partner and use various strategies to increase their reproductive success.^[10] Since bears are sexually dimorphic, sexual conflict is a primary driving force behind sexual selection influencing intra-sexual and inter-sexual competition.^[10] Unlike more social species bears, being solitary mammals, have wide-ranging habitats to locate potential mates.^[11] Due to the asynchrony of oestrous phases and lengthy parental care by females, bear populations are usually male-biased, meaning that females are more choosy and males are more competitive.^[12] Intra-sexual selection is then characterized by male-male competitions influenced by female mate choice.^[10]

Mating seasons fluctuate based on species dependent on geographical location.^[12]^[13] American black bears (Ursus amercanus), brown bears (Ursus arctos) and polar bears (Ursus maritimus) all have mating seasons occurring within a three-month duration during the spring and summer months (approximately May – July), with delayed implantation occurring in late fall (November), and cubs born within the den during early winter (January).^[12]^[13] Females, on average, mate with three to four males during a mating season and mating males have more variation, mating with one to eight females during a mating season.^[10] Since reproductive success is positively correlated with age and size in bear populations, there are also males that do not mate at all until they are able to compete with larger males.^[10] There is a very loose dominance hierarchy within bear mating systems due to their solitary nature.^[10] Majority of dominance hierarchies are found at food congregations in which population density is high and individuals are ranked based on size, mass, aggressiveness and willingness to fight.^[10] Overall, dominance hierarchies have lower adaptive strategies in solitary species and dominance is established based on encounters during the breeding season.^[11]

The mating system is generally characterised by two main components, the search phase and the encounter phase.^[13] During the breeding season, both males and females expand their home ranges to help increase the likelihood of finding potential mates.^[12]^[14] Males, especially, adapt a roaming strategy, covering a large geographic range to find receptive females and tracking them via chemoreceptors.^[12] Male bears are not considered to be territorial, but they do have large home ranges that may overlap with female home ranges, giving them access to a range of 3–15 females.^[14]

Male-male competition

Males compete for females using contest competition, scramble competition and sperm competition as mechanisms for sexual selection.^[12] The pre-copulatory mechanisms, including contest and scramble competition, are conditional mating tactics that are used based on an individual's phenotype.^[11] Males that are larger in size compete more in physical contests to access potential mates, while males that are smaller or medium-sized use scramble competition as a strategy by increasing their ranges to encounter potential mates.^[11] Age and size are positively correlated and as males mature, they grow in size and experience, monopolizing receptive females.^[11] Observations of broken canines, cuts, wounds and scars demonstrate the costs associated with contests and the importance of physical intra-sexual conflict within polygamous mating systems.^[12]

There is also post-copulatory male-male competition that has been documented in species within the genus Ursus. The presence of dual paternity within a litter implies that sperm competition may take place after copulation.^[11]^[14]

Another male strategy observed by male bears is sexually selected infanticide.^[13] This results in males killing the offspring of other males to directly and indirectly improve their own reproductive success.^[13] This can directly influence their success by mating with the female when she re-enters oestrus or indirectly by lowering intra-sexual competition with other males and resources.^[10]

Female mate choice

Female choice is based on the cost of searching for a mate and the quality of a mate.^[13] Since females are induced ovulators, studies suggest that they may have control over the paternity of their offspring.^[13] This may be done through pre- and post-copulatory counter-strategies that involve cryptic female choice and sexually selected infanticide.^[13] The hypothesis of sexually selected infanticide is a female counterstrategy that can directly and indirectly improve their fitness.^[10] This is done by selecting for infanticidal males to enforce mate and offspring recognition and indirectly by mating with multiple males in order to have multiple paternity.^[10]^[11]^[14]

Within Ursus, there may be a high variation within the mating strategies observed by both females and males, demonstrating overall plasticity depending on external factors.^[10]^[11] This demonstrates the conditional mating tactics that male bears may consider based on their age and size,^[11] as well as the counter-strategies of females, including sexually selected infanticide and cryptic female choice.^[10]

Related Research Articles

Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout most of the Northern Hemisphere and partially in the Southern Hemisphere. Bears are found on the continents of North America, South America, and Eurasia. Common characteristics of modern bears include large bodies with stocky legs, long snouts, small rounded ears, shaggy hair, plantigrade paws with five nonretractile claws, and short tails.

<span class="mw-page-title-main">Brown bear</span> Large bear native to Eurasia and North America

The brown bear is a large bear native to Eurasia and North America. It is one of the largest land carnivorans, rivaled in size only by its closest relative, the polar bear, which is much less variable in size and slightly bigger on average. The brown bear is a sexually dimorphic species, as adult males are larger and more compactly build than females. Its pelage ranges from reddish to yellowish-brown, and dark brown to cream in color. It is the only extant bear with a hump formed entirely of muscle on its shoulders. The paws are large and allow the bear to effectively dig through dirt. Its teeth are similar to those of other bears and reflect its dietary plasticity.

Polygynandry is a mating system in which both males and females have multiple mating partners during a breeding season. In sexually reproducing diploid animals, different mating strategies are employed by males and females, because the cost of gamete production is lower for males than it is for females. The different mating tactics employed by males and females are thought to be the outcome of stochastic reproductive conflicts both ecologically and socially.

A harem is an animal group consisting of one or two males, a number of females, and their offspring. The dominant male drives off other males and maintains the unity of the group. If present, the second male is subservient to the dominant male. As juvenile males grow, they leave the group and roam as solitary individuals or join bachelor herds. Females in the group may be inter-related. The dominant male mates with the females as they become sexually active and drives off competitors, until he is displaced by another male. In some species, incoming males that achieve dominant status may commit infanticide.

An ursid hybrid is an animal with parents from two different species or subspecies of the bear family (Ursidae). Species and subspecies of bear known to have produced offspring with another bear species or subspecies include American black bears, grizzly bears, and polar bears, all of which are members of the genus Ursus. Bears not included in Ursus, such as the giant panda, are expected to be unable to produce hybrids with other bears. The giant panda bear belongs to the genus Ailuropoda.

<span class="mw-page-title-main">Grizzly–polar bear hybrid</span> Cross between grizzly and polar bear

A grizzly-polar-bear-hybrid is a rare ursid hybrid that has occurred both in captivity and in the wild. In 2006, the occurrence of this hybrid in nature was confirmed by testing the DNA of a unique-looking bear who had been shot near Sachs Harbour, Northwest Territories, on Banks Island in the Canadian Arctic. The number of confirmed hybrids has since risen to eight, all of them descending from the same female polar bear.

Monogamous pairing in animals refers to the natural history of mating systems in which species pair bond to raise offspring. This is associated, usually implicitly, with sexual monogamy.

<span class="mw-page-title-main">Sexual conflict</span> Term in evolutionary biology

Sexual conflict or sexual antagonism occurs when the two sexes have conflicting optimal fitness strategies concerning reproduction, particularly over the mode and frequency of mating, potentially leading to an evolutionary arms race between males and females. In one example, males may benefit from multiple matings, while multiple matings may harm or endanger females, due to the anatomical differences of that species. Sexual conflict underlies the evolutionary distinction between male and female.

<span class="mw-page-title-main">Sexual cannibalism</span> Practice of animals eating their own mating partners

Sexual cannibalism is when an animal, usually the female, cannibalizes its mate prior to, during, or after copulation. It is a trait observed in many arachnid orders, several insect and crustacean clades, gastropods, and some snake species. Several hypotheses to explain this seemingly paradoxical behavior have been proposed. The adaptive foraging hypothesis, aggressive spillover hypothesis and mistaken identity hypothesis are among the proposed hypotheses to explain how sexual cannibalism evolved. This behavior is believed to have evolved as a manifestation of sexual conflict, occurring when the reproductive interests of males and females differ. In many species that exhibit sexual cannibalism, the female consumes the male upon detection. Females of cannibalistic species are generally hostile and unwilling to mate; thus many males of these species have developed adaptive behaviors to counteract female aggression.

Sexual dimorphism describes the morphological, physiological, and behavioral differences between males and females of the same species. Most primates are sexually dimorphic for different biological characteristics, such as body size, canine tooth size, craniofacial structure, skeletal dimensions, pelage color and markings, and vocalization. However, such sex differences are primarily limited to the anthropoid primates; most of the strepsirrhine primates and tarsiers are monomorphic.

Female copulatory vocalizations, also called female copulation calls or coital vocalizations, are produced by female primates, including human females, and female non-primates. Copulatory vocalizations usually occur during copulation and are hence related to sexual activity. Vocalizations that occur before intercourse, for the purpose of attracting mates, are known as mating calls.

Sexual swelling, sexual skin, or anogenital tumescence refers to localized engorgement of the anus and vulva region of some female primates that vary in size over the course of the menstrual cycle. Thought to be an honest signal of fertility, male primates are attracted to these swellings; preferring, and competing for, females with the largest swellings.

Sexual selection in birds concerns how birds have evolved a variety of mating behaviors, with the peacock tail being perhaps the most famous example of sexual selection and the Fisherian runaway. Commonly occurring sexual dimorphisms such as size and color differences are energetically costly attributes that signal competitive breeding situations. Many types of avian sexual selection have been identified; intersexual selection, also known as female choice; and intrasexual competition, where individuals of the more abundant sex compete with each other for the privilege to mate. Sexually selected traits often evolve to become more pronounced in competitive breeding situations until the trait begins to limit the individual's fitness. Conflicts between an individual fitness and signaling adaptations ensure that sexually selected ornaments such as plumage coloration and courtship behavior are "honest" traits. Signals must be costly to ensure that only good-quality individuals can present these exaggerated sexual ornaments and behaviors.

Sexual selection in mammals is a process the study of which started with Charles Darwin's observations concerning sexual selection, including sexual selection in humans, and in other mammals, consisting of male–male competition and mate choice that mold the development of future phenotypes in a population for a given species.

Sexual coercion among animals is the use of violence, threats, harassment, and other tactics to help them forcefully copulate. Such behavior has been compared to sexual assault, including rape, among humans.

In behavioral ecology, polyandry is a class of mating system where one female mates with several males in a breeding season. Polyandry is often compared to the polygyny system based on the cost and benefits incurred by members of each sex. Polygyny is where one male mates with several females in a breeding season . A common example of polyandrous mating can be found in the field cricket of the invertebrate order Orthoptera. Polyandrous behavior is also prominent in many other insect species, including the red flour beetle, the adzuki bean weevil, and the species of spider Stegodyphus lineatus. Polyandry also occurs in some primates such as marmosets, mammal groups, the marsupial genus' Antechinus and bandicoots, around 1% of all bird species, such as jacanas and dunnocks, insects such as honeybees, and fish such as pipefish.

Sperm competition is a form of post-copulatory sexual selection whereby male sperm simultaneously physically compete to fertilize a single ovum. Sperm competition occurs between sperm from two or more rival males when they make an attempt to fertilize a female within a sufficiently short period of time. This results primarily as a consequence of polyandrous mating systems, or due to extra-pair copulations of females, which increases the chance of cuckoldry, in which the male mate raises a child that is not genetically related to him. Sperm competition among males has resulted in numerous physiological and psychological adaptations, including the relative size of testes, the size of the sperm midpiece, prudent sperm allocation, and behaviors relating to sexual coercion, however this is not without consequences: the production of large amounts of sperm is costly and therefore, researchers have predicted that males will produce larger amounts of semen when there is a perceived or known increase in sperm competition risk.

Infanticide in non-human primates occurs when an individual kills its own or another individual's dependent young. Five hypotheses have been proposed to explain infanticide in non-human primates: exploitation, resource competition, parental manipulation, sexual selection, and social pathology.

Primate sociality is an area of primatology that aims to study the interactions between three main elements of a primate social network: the social organisation, the social structure and the mating system. The intersection of these three structures describe the socially complex behaviours and relationships occurring among adult males and females of a particular species. Cohesion and stability of groups are maintained through a confluence of factors, including: kinship, willingness to cooperate, frequency of agonistic behaviour, or varying intensities of dominance structures.

Formerly or currently considered subspecies or populations of brown bears have been listed as follows:

References

↑ "ADW: Ursus: CLASSIFICATION". animaldiversity.ummz.umich.edu. Retrieved 4 April 2018.
↑ Wilson, D. E.; Reeder, D. M., eds. (2005). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. ISBN 978-0-8018-8221-0. OCLC 62265494.
↑ "Brown Bear Fact Sheet". library.sandiegozoo.org. Archived from the original on 16 February 2018. Retrieved 4 April 2018.
↑ "Polar Bear Fact Sheet". library.sandiegozoo.org. Archived from the original on 24 April 2016. Retrieved 4 April 2018.
↑ "Definition of URSUS". www.merriam-webster.com. Retrieved 4 April 2018.
↑ "Ursus | Define Ursus at Dictionary.com". Archived from the original on 2012-04-25. Retrieved 2014-03-17.
↑ "Mexican black bear – Bear Conservation". www.bearconservation.org.uk. Retrieved 2018-01-29.
↑ "West Mexico black bear – Bear Conservation" . Retrieved 2018-01-29.
↑ Seton, Ernest Thompson (2015-07-30). Wahb: The Biography of a Grizzly. University of Oklahoma Press. ISBN 9780806152325.
1 2 3 4 5 6 7 8 9 10 11 12 13 STEYAERT, Sam M. J. G.; ENDRESTØL, Anders; HACKLÄNDER, Klaus; SWENSON, Jon E; ZEDROSSER, Andreas (2012-01-01). "The mating system of the brown bear Ursus arctos". Mammal Review. 42 (#1): 12–34. doi:10.1111/j.1365-2907.2011.00184.x. ISSN 1365-2907.
1 2 3 4 5 6 7 8 9 Kovach, Adrienne I; Powell, Roger A (2003-07-01). "Effects of body size on male mating tactics and paternity in black bears, Ursus americanus". Canadian Journal of Zoology. 81 (#7): 1257–1268. doi:10.1139/z03-111. ISSN 0008-4301.
1 2 3 4 5 6 7 Derocher, Andrew E.; Andersen, Magnus; Wiig, Øystein; Aars, Jon (2010-05-01). "Sexual dimorphism and the mating ecology of polar bears (Ursus maritimus) at Svalbard". Behavioral Ecology and Sociobiology. 64 (#6): 939–946. doi:10.1007/s00265-010-0909-0. ISSN 0340-5443. S2CID 36614970.
1 2 3 4 5 6 7 8 Bellemain, Eva; Zedrosser, Andreas; Manel, Stéphanie; Waits, Lisette P.; Taberlet, Pierre; Swenson, Jon E. (2006-02-07). "The dilemma of female mate selection in the brown bear, a species with sexually selected infanticide". Proceedings of the Royal Society of London B: Biological Sciences. 273 (#1584): 283–291. doi:10.1098/rspb.2005.3331. ISSN 0962-8452. PMC 1560043 . PMID 16543170.
1 2 3 4 Schenk, Anita; Kovacs, Kit M. (1995). "Multiple mating between black bears revealed by DNA fingerprinting". Animal Behaviour. 50 (#6): 1483–1490. doi:10.1016/0003-3472(95)80005-0. S2CID 54316843.

External links

Data related to ursus at Wikispecies
Media related to Ursus (genus) at Wikimedia Commons

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[1] "ADW: Ursus: CLASSIFICATION". animaldiversity.ummz.umich.edu. Retrieved 4 April 2018.

[2] Wilson, D. E.; Reeder, D. M., eds. (2005). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. ISBN 978-0-8018-8221-0. OCLC 62265494.

[3] "Brown Bear Fact Sheet". library.sandiegozoo.org. Archived from the original on 16 February 2018. Retrieved 4 April 2018.

[4] "Polar Bear Fact Sheet". library.sandiegozoo.org. Archived from the original on 24 April 2016. Retrieved 4 April 2018.

[5] "Definition of URSUS". www.merriam-webster.com. Retrieved 4 April 2018.

[6] "Ursus | Define Ursus at Dictionary.com". Archived from the original on 2012-04-25. Retrieved 2014-03-17.

[7] "Mexican black bear – Bear Conservation". www.bearconservation.org.uk. Retrieved 2018-01-29.

[8] "West Mexico black bear – Bear Conservation" . Retrieved 2018-01-29.

[9] Seton, Ernest Thompson (2015-07-30). Wahb: The Biography of a Grizzly. University of Oklahoma Press. ISBN 9780806152325.

[:0-10] 1 2 3 4 5 6 7 8 9 10 11 12 13 STEYAERT, Sam M. J. G.; ENDRESTØL, Anders; HACKLÄNDER, Klaus; SWENSON, Jon E; ZEDROSSER, Andreas (2012-01-01). "The mating system of the brown bear Ursus arctos". Mammal Review. 42 (#1): 12–34. doi:10.1111/j.1365-2907.2011.00184.x. ISSN 1365-2907.

[:1-11] 1 2 3 4 5 6 7 8 9 Kovach, Adrienne I; Powell, Roger A (2003-07-01). "Effects of body size on male mating tactics and paternity in black bears, Ursus americanus". Canadian Journal of Zoology. 81 (#7): 1257–1268. doi:10.1139/z03-111. ISSN 0008-4301.

[:2-12] 1 2 3 4 5 6 7 Derocher, Andrew E.; Andersen, Magnus; Wiig, Øystein; Aars, Jon (2010-05-01). "Sexual dimorphism and the mating ecology of polar bears (Ursus maritimus) at Svalbard". Behavioral Ecology and Sociobiology. 64 (#6): 939–946. doi:10.1007/s00265-010-0909-0. ISSN 0340-5443. S2CID 36614970.

[:3-13] 1 2 3 4 5 6 7 8 Bellemain, Eva; Zedrosser, Andreas; Manel, Stéphanie; Waits, Lisette P.; Taberlet, Pierre; Swenson, Jon E. (2006-02-07). "The dilemma of female mate selection in the brown bear, a species with sexually selected infanticide". Proceedings of the Royal Society of London B: Biological Sciences. 273 (#1584): 283–291. doi:10.1098/rspb.2005.3331. ISSN 0962-8452. PMC 1560043 . PMID 16543170.

[:4-14] 1 2 3 4 Schenk, Anita; Kovacs, Kit M. (1995). "Multiple mating between black bears revealed by DNA fingerprinting". Animal Behaviour. 50 (#6): 1483–1490. doi:10.1016/0003-3472(95)80005-0. S2CID 54316843.

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