Yellowstone bison fetal development and phenology of parturition

Journal of Wildlife Management
By: , and 



Knowledge of Yellowstone bison (Bison bison) parturition patterns allows managers to refine risk assessments and manage to reduce the potential for transmission of brucellosis between bison and cattle. We used historical (1941) and contemporary (1989–2002) weights and morphometric measurements of Yellowstone bison fetuses to describe fetal growth and to predict timing and synchrony of parturition. Our method was supported by agreement between our predicted parturition pattern and observed birth dates for bison that were taken in to captivity while pregnant. The distribution of parturition dates in Yellowstone bison is generally right-skewed with a majority of births in April and May and few births in the following months. Predicted timing of parturition was consistently earlier for bison of Yellowstone's northern herd than central herd. The predicted median parturition date for northern herd bison in the historical period was 3 to 12 days earlier than for 2 years in the contemporary period, respectively. Median predicted birth dates and birthing synchrony differed within herds and years in the contemporary period. For a single year of paired data, the predicted median birth date for northern herd bison was 14 days earlier than for central herd bison. This difference is coincident with an earlier onset of spring plant growth on the northern range. Our findings permit refinement of the timing of separation between Yellowstone bison and cattle intended to reduce the probability of transmission of brucellosis from bison to cattle.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Yellowstone bison fetal development and phenology of parturition
Series title Journal of Wildlife Management
DOI 10.2193/0022-541X(2005)69[1716:YBFDAP]2.0.CO;2
Volume 69
Issue 4
Year Published 2005
Language English
Publisher Wildlife Society
Publisher location Washington
Contributing office(s) Northern Rocky Mountain Science Center
Description 15 p.
First page 1716
Last page 1730
Country United States
State Idaho, Montana, Wyoming
Other Geospatial Yellowstone National Park
Online Only (Y/N) N
Additional Online Files (Y/N) N