They are currently found in disjunct populations in protected areas throughout western North America. American bison inhabit the grasslands, boreal regions, scrublands of North America. Abstract Prepubertal testicular development was evaluated in young North American bison Bison bison bulls over a 12 months period, by following various parameters of semen quality intended to measure sexual maturity level. Chapter 12 White Mans Caress. Questions and comments may be addressed to library sandiegozoo. Although San Diego Zoo Global makes every attempt to provide accurate information, some of the facts may become outdated or replaced by new research findings.
Subadults and young adults formed a much larger part of the Wood Buffalo National Park samples Fuller ; aged animals formed more of the Yellowstone sample. Sexual maturation also may be later in the Yellowstone population of this study compared with herds elsewhere. Temperatures and snowfall are for the park interior. Adult male bison may be "biologically expendable" according to Etkin , who states that sexual dimorphism termed aggressive potential in bison interferes with male survival. Size Male Female Height: Conservation Status in the Wild: Figure 24 shows population trends based on actual counts post-reduction, precalving from through for the entire park, as well as for the wintering subunits of Lamar, Pelican, and Mary Mountain.
The onset of puberty in North American bison (Bison bison) bulls - ScienceDirect
More were trapped during the severe winter of than in Incidence of pregnancy by age class for two Yellowstone studies 25 years apart are compared in Table 10 as an indication of sexual maturity in the female population. Later increases were apparently offset by reductions Lamar , or by reductions in combination with periodically severe environmental conditions Pelican, Mary Mountain. The temporary effect of even small reductions on low population levels was apparent, but some increase with recruitment of more breeding females into the population expected by did not occur. There were significant increases with age in individual progressive motility, gross motility, concentration, density, and volume but not in the percent of live sperm.
Description: Wood Buffalo National Park, compared with Yellowstone, is colder, but has less snow and fewer periods of crusting conditions during the winter. Variation in subadult mortality rates probably occurs, but cannot be judged from the limited data. Traditionally, American bison were split into two subspecies, the Wood and Plains bison. Bison population trends from population counts, The reduction in the Mary Mountain area may have started the downward trend shown between the counts of and