Abstract - Mother-Daughter Interactions in American Bison (Bison bison): Factors Associated with Individual Variation
Green, Wendy Carroll Hortenstine. 1987. Mother-daughter interactions in American bison (Bison bison): Factors associated with individual variation. Ph.D. Dissertation. City University of New York. 202+ p.
To describe developmental changes and individual variation in bison mother-daughter relations, I observed 13 dyads from birth to 1.5 years and collected supplementary data on the first five years for 48 daughters at Wind Cave National Park.
Pre-weaning spatial relations change minimally; mothers and calves follow each other infrequently and are often far apart. Bison appear to be neither hiders nor followers, but incorporate aspects of both strategies. Old and young mothers invest differently in offspring; while older cows provide more nursing care, young mothers contact calves more often. Maternal experience mitigates disruptive effects of tending by bulls on mother-calf relations.
Weaning occurs gradually, with little conflict. The end of weaning varies with the mother's subsequent reproductive status: pregnant cows stop nursing at 9-12 months; barren cows at 17-21. After weaning and the birth of the mother's next calf, daughters spend less time near mothers, but proximity-maintenance behaviors change little. While post-weaning associations with mothers vary in longevity, most continue at least until sexual maturity. Where bonds endure, mothers' efforts at proximity-maintenance are largely responsible.
Younger mothers and later-born calves behave as if to compensate for social and physical disadvantages. Late-born calves and their mothers synchronize movements more than other dyads. Young mothers have closer, longer-lasting relations with daughters. Larger daughters are born earlier, retain natal coats longer, achieve higher rank, and may calve earlier than smaller daughters; they are also more independent of mothers. Prolonged care by barren mothers enhances offspring size and, possibly, reproduction.