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GRIZZLY BEAR

IDENTIFICATION: A huge bear (7–10 feet tall) with dark brown, golden, cream, or black fur. DISTRIBUTION: Northern North America, Europe, central Asia, Middle East, north Africa. HABITAT: Tundra, forests. STUDY AREA: Yellowstone National Park, Wyoming; subspecies U.a. horribilis.

BLACK BEAR

IDENTIFICATION: A smaller bear (4–6 feet) with coat color ranging from black to gray, brown, and even white. DISTRIBUTION: Canada and northern, eastern, and southwestern United States. HABITAT: Forest. STUDY AREA: Jasper National Park, Alberta; Prince Albert National Park, Saskatchewan, Canada; subspecies U.a. altifrontalis.

Social Organization

Grizzly Bears and Black Bears are largely solitary animals. Some Grizzly populations, however, tend to aggregate around abundant food sources such as salmon, marine mammals (stranded onshore), garbage dumps, and even insect swarms; fairly complex social interactions may develop in these contexts. The heterosexual mating system is polygamous, as both males and females generally mate with multiple partners; males do not contribute to parenting.

Description

Behavioral Expression: Female Grizzly Bears sometimes bond with each other and raise their young together as a single family unit. The two mothers become inseparable companions, traveling and feeding together throughout the summer and fall seasons as they share in the parenting of their cubs. Female companions have not been observed interacting sexually with one another, however. A bonded pair jointly defends their food (such as Elk or Bison carcasses), and the two females also protect one another and their offspring (including defending them against attacks by Grizzly males). The cubs regard both females as their parents, following and responding to either mother equally; bonded females occasionally also nurse each other’s cubs. If one female dies, her companion usually adopts her cubs and looks after them along with her own.

As winter approaches and Grizzlies prepare for hibernation, female coparents often continue to associate with one another. Foraging together late into the fall, they are apparently reluctant to end their relationship and may even delay the onset of their own sleep. Although paired females do not hibernate together, they frequently visit each other (with their cubs) prior to hibernation, staying nearby while their partner prepares her den. They also sleep together outside their denning sites during this final preparatory period and only retreat to their separate dens once the snow gets too deep. Most Grizzlies seek solitude prior to hibernating and locate their winter dens miles away from each other (and with rugged terrain separating them), but bonded females often hibernate relatively close to one another. Such females have even been known to abandon their traditional denning locations to be nearer to their coparent. One female, for example, moved her usual den site more than 14 miles to be closer to her companion. Pair-bonds are not usually resumed after hibernation, although one female may adopt her companion’s yearling offspring the following season. The average age of a bonded female is about 11 years, although Grizzlies as young as 5 and as old as 19 have formed bonds with other females. Companions may be of the same age, or one female might be several years older than the other. Sometimes more than two females are involved: three Grizzlies may form a strongly bonded “triumvirate,” and groups of four or five females have even been known to associate (sometimes also forming pair- or trio-bonds within such a group).

Younger male Black Bears (adolescents and cubs) sometimes mount their siblings, both male and female. One male approaches another with his ears in a CRESCENT configuration (facing forward and perpendicular from the head), then rears up on his hind legs in a STANDING OVER position, in which he places his front paws on the other male’s back. This develops into sexual mounting as he clasps his partner and gently bites the loose skin on his shoulder, sometimes making pelvic thrusts. The other male often rolls over and begins play-fighting with the mounting male, pawing and biting at him.

A two-mother family: bonded female Grizzly Bears in Wyoming with their four cubs

Intersexual or hermaphrodite Black and Grizzly Bears occur in some populations. These individuals are genetically female and have female internal reproductive organs, combined with various degrees of external male genitalia. In some cases, they have a penislike organ (complete with a penis bone or BACULUM) that is not connected to the internal reproductive organs, while in others the penis is more fully developed, serving as both a genital orifice connected to the womb as well as a urinary organ. Most transgendered Bears are mothers, mating with males and bearing offspring. Some individuals actually copulate and give birth through their “penis”: their male partner inserts his organ into the tip of the intersexual Bear’s phallus, and the resulting offspring emerge through the penis as well.

Frequency: Female bonding and coparenting among Grizzly Bears occur sporadically. In a 12-year study of one population, for example, bonds between females were observed during 4 of those years (a third of the study period), with roughly 20 percent of all females participating in same-sex bonding and coparenting at some point in their life (usually 1–2 years out of an adult life span of 7–12 years). About 9 percent of all Grizzly cubs are raised in families headed by two (or more) pair-bonded mothers (constituting about 4 percent of all families). Sexual activity between younger male Black Bears occurs only occasionally, comprising perhaps less than 2 percent of their play. The incidence of intersexual Bears is probably sporadic as well, although some populations appear to have fairly high proportions: in Alberta, for example, researchers found that 4 out of 38 Black Bears (11 percent) and 1 of 4 Grizzlies were transgendered.

Orientation: Extended heterosexual pair-bonding and parenting by male-female couples do not occur among Grizzly Bears; however, only a subset of females bond with each other and coparent their young. Thus, some individuals are probably more inclined to form same-sex attachments than others, and these females may even develop same-sex bonds on more than one occasion. Although such females mate with males (and may not bond with females in other years), their primary social relationship during the time they are bonded is with their female companion (and their young). Male Black Bears participate in homosexual mounting only as youngsters and adolescents; most probably go on to mate heterosexually as adults.