Ursus (mammal)

Ursus is a genus in the family Ursidae (bears) that includes the widely distributed brown bear, the polar bear, the American black bear, and the

Asian black bear. The name is derived from the Latin ursus, meaning bear.

Taxonomy and systematics

Extant species

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".

Fossil species

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

Mating system ecology

The mating systems within the genus Ursus are primarily classified as polygynous, polyandrous and promiscuous. Both males and females mate with more than one partner and use various strategies to increase their reproductive success. 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. Intra-sexual selection is then characterized by male-male competitions influenced by female mate choice. 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). Males, especially, adapt a roaming strategy, covering a large geographic range to find receptive females and tracking them via chemoreceptors.