Ecology of a prairie mule deer population

The ecology of a mule deer (Odocoileus hemionus) population inhabiting an eastern Montana prairie, was studied during 1975-1986, using periodic aerial surveys and radioed and neckbanded deer.Spring population size increased by 29%/year from 1976 to 1983, stabilized at approximately 1,080 deer during 1983-1984, and declined 61% during 1984-1986.An average of 42% of the adult females successfully weaned > 1 fawn, resulting in autumn, winter, and spring fawn:doe ratios averaging 56:100, 55:100, and 35:100, respectively.Annual mortality rates for fawns, adult females, and adult males averaged 70%, 23%, and 63%, respectively; harvest rates averaged 3%, 19%, and 59%, respectively.Deer distribution was highly aggregated across the area.Mixed groups of males and females were uncommon, though distributions of males and females overlapped significantly.Individual females exhibited 1 of 3 movement patterns: yearlong residency, spring and autumn migration, or late summer and late autumn migration.Annual home ranges averaged 4.4 km2.Females and mature, males demonstrated a high degree of fidelity to traditional herd ranges,, but yearling males did not.Areas of topographic diversity in winter, and mesic sites in summer were preferred.Interspersion of habitat complexes influenced both distribution and home range size.Environmental variability caused specific responses by mule deer, and was reflected in variable fawn recruitment rates.Population regulation seemed to be influenced by the limited availability of high,quality forage during late summer.Spring population size of white-tailed deer (0. virginianus) peaked at 335 deer.Population dynamics of both species were similar, except during 1984, when 60% of the female whitetails were harvested.Significant interspecific overlap occurred, and the 2 species demonstrated no intrinsic avoidance mechanisms.Whitetailed deer preferred areas with overhead cover adjacent to agricultural fields, used larger annual home ranges (9.98 km2) and showed much less home range fidelity than mule deer.Pronghorn antelope (Antilocapra americana) occurred on the area at densities similar to white-tailed deer, used open habitats, and had little impact on the mule deer population.