James H. Noyes

Effects of bull age on conception dates and pregnancy rates of cow elk

Productivity of cows in many Rocky Mountain elk (Cervus elaphus nelsoni) populations of northeast Oregon has declined over the last 30 years. Numbers of mature bulls declined concurrently, suggesting a potential link that accounts for declining productivity. We evaluated the influence of bull age on conception dates and pregnancy rates of cow elk within a 78-km 2 enclosure on the Starkey Experimental Forest and Range in northeast Oregon from 1989 to 1993. We allowed a single cohort of bulls to mature from 1 1/2 to 5 1/2 years and function as principal herd sires. Subsequent male offspring were reduced in numbers through hunting and trapping. We estimated conception dates, pregnancy rates, body condition, age, and lactation status of cows killed in December. Conception dates occurred earlier as bull age increased (P = 0.0001) and were significantly different between bulls ≤ 2 years and ≥ years of age. The rut became more synchronous and shortened from 71 days (n = 26) when breeding was by yearling bulls to 41 days (n = 33) when 5-year-old bulls were the principal sires. Pregnancy rates increased from 89 to 97% as bull age increased, but not significantly (P = 0.62). Cow body condition was highest (P = 0.004) in 1989 when breeding was by yearling bulls. To enhance herd productivity we recommend that elk hunting seasons be designed so that older bulls ( ≥ 3 yr) are retained in the population.

Effects of Male Age and Female Nutritional Condition on Elk Reproduction

Spring calf:cow ratios in some Rocky Mountain elk (Cervus elaphus) populations of northeast Oregon have declined by almost 80% over the last 40 years. Studies have identified the age of breeding males and the nutritional condition of females as potentially contributing factors. We conducted a study in 2 trials, from 1989 to 1993 and from 1995 to 1999, to assess the effects of male age on conception dates and pregnancy rates of female elk in northeast Oregon. Results of the first trial, reported previously, showed a significant influence of male age on conception dates but not on pregnancy rates. The second trial, reported here, was intended to validate findings of the first. trial and to evaluate the interaction of male age and female nutritional condition. We managed an elk population within a 78-km2 enclosure to allow a single cohort of males to function as herd sires as they matured from 1.5 to 5.5 years of age. From animals killed in December, we estimated pregnancy rates, age, nutritional condition (kidney fat index, [MFI]), and lactation status of females and the conception dates of their fetuses. Mean conception dates occurred 1 week earlier as male age increased and were related to KFI in females. Nutritional condition of female elk was 67% higher in 1995 when breeding was by yearling males than in years when breeding was by 4-year-old or 5-year-old males. Pregnancy rates did not differ among ages of males. We used analysis of covariance with female nutritional condition as the covariate to evaluate the interactive effects of male age and female nutritional condition on conception dates of females bred by males of different ages across 2 trials. Mean conception dates (adjusted for female nutritional condition) pooled by age of males decreased from 4 October with yearling male sires to 21 September with 5-year-old male sires. Mean KFI of pregnant, lactating female elk was 118 during the validation and 148 during the initial trial. Pregnancy rates did not differ by male age between trials. We stress the importance of understanding the interactions between age of males and nutritional condition of females prior to interpreting the results of management strategies designed to retain older males because of the many factors that affect calf elk survival.

Diet and Nutrition of Breeding Female Redhead and Canvasback Ducks in Nevada

Diet, nutrition, and foraging strategies of breeding female canvasback (Aythya valisineria) and redhead ducks (A. americana) were studied by collecting foraging birds in 1980 and 1981 at Ruby Lake National Wildlife Refuge (Ruby Lake NWR). Female canvasbacks consumed a small number of food items, most of which were not abundant in the marsh. The diet of redheads changed with each stage of the reproductive cycle; they usually foraged on the most abundant foods in the marsh. Nutrient and energy content of the diet of canvasbacks varied little from laying through brooding, but both were quite variable in the diet of female redheads. Female canvasbacks retained large lipid reserves during formation of the clutch but used 68% from late laying to the incubation stage. Redheads expended 46% of their lipid reserves during formation of the clutch and 30% from late laying to incubation. J. WILDL. MANAGE. 49(1):203-211 Food habits and changes in body reserves of breeding waterfowl have received much attention, especially for dabbling ducks (Anas spp.) (Krapu 1974, 1981; Swanson et al. 1974b; Serie and Swanson 1976), wood ducks (Aix sponsa) (Drobney and Fredrickson 1979), and geese (Chen, Branta) (Harwood 1977; Ankney and MacInnes 1978; Raveling 1979). Generally, lipid reserves are accumulated before laying as a result of consumption of plant foods high in carbohydrates. During laying, females feed on foods high in protein (invertebrates by ducks, sprouting grasses by geese) to supply the protein necessary for egg production, and begin to utilize their lipid reserves. Restriction of food intake during incubation results in rapid depletion of lipid reserves. By the end of the incubation period, females have nearly exhausted their lipid reserves. The diet and nutrient cycles of breeding diving ducks (Aythya spp.), which feed to a greater extent on animal foods throughout the year than do dabbling ducks (Cottam 1939, Martin et al. 1951), have not been reported. W investigated the relationship between diet and body reserves of two closely related species of diving ducks, the redhead and the canvasback. These two species occur together over much of their range and have similar habitat r quirements during the breeding season (Weller 1959). However, they pursue different nesting strategies: the redhead is semiparasitic, whereas the canvasback is not (Weller 1959). Thus, their foods and nutrient cycles during the br eding season might be expected to be different, even when both species occur in the same marsh. The objectives of this study were to: (1) determine the foods consumed, preference for foods, and nutrient content of the diet of female canvasbacks and redheads; (2) determine changes in body weight and body reserves durIPresent address: 6132 SW 46th Ave., Portland, OR 97221. This content downloaded from 157.55.39.120 on Mon, 05 Sep 2016 06:18:07 UTC All use subject to http://about.jstor.org/terms 204 REDHEAD AND CANVASBACK DIETS * Noyes and Jarvis J. Wildl. Manage. 49(1):1985 ing reproduction; and (3) relate diet and changes in body reserves to their respective nesting

Foods of canvasbacks and redheads in Nevada: paired males and ducklings

The diets of canvasback (Aythya valisineria) and redhead (A. americana) paired males and ducklings were the same as those of their mates and hens, respectively, during 1980-81 on Ruby Lake National Wildlife Refuge (RLNWR), Nevada. Diets of canvasback ducklings were high in protein and energy, but those of redhead ducklings were low. J. WILDL. MANAGE. 50(2):199-203 Paired male ducks and ducklings may have different food requirements than accompanying females. Paired males during the prelaying and laying period engage in defense of the female and a feeding territory (Dwyer 1974, Ashcroft 1976) and presumably should require high energy foods. Female ducks consume foods high in energy prior to nesting for deposition of energy reserves (Krapu 1974, 1981; Serie and Swanson 1976; Drobney 1980, 1982) and during the postlaying period to replace lipid stores exhausted during egg laying and incubation (Krapu 1974, Drobney 1982). Foods high in protein content are consumed during laying to meet the needs for egg formation (Krapu 1974, Drobney 1982). Thus, at least during the laying period, paired males and females may have different food requirements. Likewise, ducklings, which require foods high in protein for growth (Marshall 1951, Krapu and Swanson 1978), may need to consume different foods than brooding females that need foods high in energy, at least early in the brooding period. Molting for adult females may begin in the late stages of the brooding period, requiring foods high in protein content (Krapu and Swanson 1978). As part of a study on diet and nutrition of breeding canvasbacks and redheads (Noyes 1983, Noyes and Jarvis 1985), we determined if paired males and ducklings consumed diets different from associated adult females in response to differing nutritional requirements. This study was funded by the U.S. Fish and Wildl. Serv. through the North. Prairie Wildl. Res. Cent. and conducted under the auspices of the Oreg. Coop. Wildl. Res. Unit. We thank S. H. Bouffard, T. J. Bowser, F. W. Cameron, R. W. Carmichael, D. L. Eisele, P. A. Frazier, and C. L. Noyes for field and laboratory assistance. Other helpful assistance was provided by K. W. Cummins, L. R. D. Johnston, and R. L. Post for plant and invertebrate identification; E. R. Beals and C. L. Noyes for computer and statistical analyses; and J. R. Serie for helpful comments duri g the study. J. A. Crawford, D. S. Gilmer, G. L. Krapu, and D. E. Sharp reviewed early drafts of the manuscript. This is Oreg. Agric. Exp. Stn. Tech. Pap. 7425.

Reproduction in North American elk Cervus elaphus: paternity of calves sired by males of mixed age classes

Our objective was to examine effects of groups of mixed numbers and ages of male North American elk Cervus elaphus on the reproductive performance of females. We conducted research at the Starkey Experimental Forest and Range in northeastern Oregon, USA, during 1993-2000. Each spring in late March, we released 40 female elk, eight yearling (9-month old) male elk and 2-8 branch-antlered elk (i.e. ≥ 2 years of age during rut the following autumn) into a 622-ha fenced pasture. Elk were gathered during autumn and early winter, and were brought to winter feeding grounds where blood samples were drawn to determine pregnancy status. The following spring, females were released into an 80-ha pasture prior to parturition. We searched for and captured newborn calves and obtained ear-punch samples for genetic analysis. We used 18 microsatellite loci to establish paternity of each calf. We varied the ratio of mature males (i.e. ≥ 3 years old) to female ratio from 0.03 to 0.21. As expected, mature males (older and heavier) were more successful in siring calves than were younger males. Within age classes, however, body mass in spring did not accurately predict mating success in autumn. Reproductive rates were not affected by season of grazing by cattle, yearling male to female ratio or mature male to female ratio. Sire age had no effect on mean dates of calf births or on calf weights. Neither sire age nor season of grazing by cattle had significant effects on calf weights; however, mean date of birth was significantly earlier when cattle grazing occurred during the previous autumn than when cattle grazed during the preceding spring. Furthermore, the number of calves sired by yearling males was greater when cattle grazing occurred during autumn, than when grazing occurred during spring. In the years with disruptive cattle grazing during rut, females mated not only with yearling males, in general, but often with those who were lighter in body mass during the previous spring than others in the same cohort. The extent to which those yearling males are untested in combat with older, dominant herd bulls may have genetic consequences leading to differences in fitness and subsequent reductions in calf survival. Please note that the supplementary information, including Appendix SI mentioned in this article, is available in the online version of this article, which can be viewed at www.wildlifebiology.com