Winter Pregnancy Rates and Subsequent Fall Cow/Calf Ratios in Elk

Abstract

Free-ranging elk (Cervus canadensis) wintering at the Hardware Ranch Game Management Unit near Logan, Utah were diagnosed for pregnancy by rectal palpation. Anatomical changes in gravid and nongravid uteri of cattle were found directly applicable to elk. Correlations between winter pregnancy rates and subsequent fall cow/calf ratios indicated that pregnancy checks would give wildlife managers a sixto eight-month forecast of an elk herd's productivity, assuming preand postpuberal losses remained constant. J. WILDL. MANAGE. 38(4):789-791 Intensified elk management programs require detailed reproductive information to provide a knowledgeable basis for herd manipulations. Available information on various species demonstrates that reproductive processes vary from one population to another, as variables such as climate, weather, and forage change. Rectal palpation generally is accepted to be the most reliable method of detecting pregnancies in bovine, particularly in the early and midgestational periods (Arthur 1964). Greer and Hawkins (1967) first reported the rectal approach for pregnancy determinations in elk. Fig. 1 shows the close correlation between fetal sizes of elk and cattle. It indicates similar fetal growth curves for these two species. METHODS AND MATERIALS The Cache elk herd and the Hardware Ranch Game Management Unit near Logan, Utah provide excellent opportunities to study reproductive parameters. In cooperation with the Utah Division of Wildlife Resources, free-ranging elk were trapped on the winter feed grounds at the Ranch and cows aged as mature or yearling (Hancock and Low 1956) were examined for pregnancy by rectal palpation during the 196970, 1970-71, and 1971-72 winters. A plastic arm-length glove was used to protect the hand and arm. After the elk were properly restrained in a Powder River squeeze chute, the gloved hand was lubricated and inserted into the rectum. Internal organs were contacted; the genitalia palpated, and the animal's reproductive status recorded. Similarities between cattle and elk uterine and ovarian locations and structure, as well as the senior author's previous experience with cattle, increased the efficiency of elk palpation. RESULTS AND CONCLUSIONS Nineteen adult and 5 yearling elk were trapped and rectally palpated during the 1969-70 winter, 60 adults and 23 yearlings in 1970-71, and 39 adults and 13 yearlings in 1971-72 (Table 1). There were no significant differences between the pregnancy rates observed during the 3-year study when statistically tested by chi-square. It is assumed that representative samples were taken and no preor postpuberal losses 1 A contribution of the Utah Cooperative Wildlife Research Unit, Utah State University, Utah Division of Wildlife Resources, U. S. Fish and Wildlife Service, and the Wildlife Management Institute, cooperating. 2 Present address: Ralston Purina Company, Checkerboard Square, St. Louis, Missouri 63199. J. Wildl. Manage. 38 (4):1974 789 This content downloaded from 157.55.39.149 on Sat, 09 Jul 2016 06:59:36 UTC All use subject to http://about.jstor.org/terms 790 WINTER PREGNANCY RATES IN ELK o Follis and Spillett