Jack Ward Thomas

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.

Nutrition-growth relations of elk calves during late summer and fall

We report nutrition-growth relations in juvenile Rocky Mountain elk (Cerous elaphus nelsoni) from mid-August through mid-November. Data were generated from 3, 18-day experimental trials in 1993 with 42 calves, and from general feeding and growth data collected in 1991 with 25 calves. Intake of digestible energy was linearly correlated with growth rate and accounted for 53-89% of the variation in calf growth. Maximum daily digestible energy intake and growth rates were 368 kcal/kg BM 0.75 and 0.70 kg/day in late August and early September and 342 kcal/kg BM 0.75 and 0.33 kg/day in mid-November. Intake-specific growth rates declined after late September, suggesting a seasonal influence on growth-intake relations. We developed a deterministic model of growth to compare body mass dynamics over autumn of calves on an optimum diet (i.e., 3.3-2.95 kcal of digestible energy/g of forage) versus calves on diets available to free-ranging elk (2.66-1.86 kcal/g). Model projections indicated a 21% difference in body mass of the 2 groups by mid-December due to the lower concentration of digestible energy in diets of free-ranging calves. Our results confirm the importance of nutrition in late summer and fall for growth of elk calves, suggest a mechanism linking dietary quality during this time to winter survival, and demonstrate the importance of evaluating forage quality for reliable assessment of habitat quality on elk summer and autumn ranges.

The Reproductive Cycle of Male White-Tailed Deer in Central Texas

A study of 50 male Texas white-tailed deer (Odocoileus virginianus) showed the reproductive cycle occurred in three phases: primary development, full production, and rest. This three-phase cycle had not been described previously. Initiation of antler growth was accompanied by partial stimulation of testicular development during the primary development phase. In the full production phase, the seminiferous tubules were stimulated further by some factor, presumably testosterone, which enabled spermatogenesis to proceed to maturity. These changes coincided with the shedding of the velvet from the antlers. Involution of the seminiferous tubules and abscision of the antlers were followed by a short period of testicular rest and were characteristic of the rest, the third phase. Peak spermatic production occurred in the latter half of November and early December. Fifty male specimens of Texas whitetailed deer from the Edwards Plateau of Texas in Mason, McCulloch, and Sutton counties, were collected to determine the normal reproductive cycle. A description of the reproductive behavior in white-tailed deer of the nearby Llano Basin has been published, but was primarily concerned with herd reproduction as determined by examination of female reproductive tracts and census data (Teer 1964). This study was designed to extend separate observations of the reproductive cycle of male deer in New York (Cheatum and Morton 1946), Massachusetts (Wislocki 1943), and southern Texas (Illige 1951). Our gratitude is expressed for the help and encouragement of Dr. C. H. Bridges, Mrs. Lucille Schultz, and R. Gardner. Additional thanks are expressed to Mrs. Dorthea Robinson for her typing skill and editorial efforts. METHODS Two male deer were collected at biweekly intervals throughout the year from September 1, 1962, to August 31, 1963, in Mason, McCulloch, and Sutton counties in the Edwards Plateau of central Texas. Immediately after collection, the deer were weighed and their ages estimated using the technique described by Severinghaus (1949). A necropsy was performed to observe the gross appearance of all organs and antler development of the deer. The testes were incised and preserved in 10 percent buffered formalin along with representative tissues of other organs. After fixation, the testes and accessory sex glands were dissected free from extraneous material and weighed. Tissue sections were cut from the testes approximately 4 mm from the incised surface, imbedded in paraffin, and sectioned at 6 microns. In the preparation of the sections for microscopic study, hematoxylin and eosin stains were routinely employed. Detailed observations of the sections were recorded and correlated with the gross appearance, testicular weights, and antler development. 1 This is a contribution of a cooperative project between the Texas Parks and Wildlife Department and the Department of Veterinary Pathology, College of Veterinary Medicine, through the Agricultural Experiment Station, Texas A & M University, supported by Pittman-Robertson Project W-90-R.

A Die-off in White-Tailed Deer of the Central Mineral Region of Texas

A die-off of 20,000-31,000 white-tailed deer (Odocoileus virginianus) occurred during January-August, 1962, on a 350,000-acre study area in the Central Mineral Region of Texas. This loss was indicated by both deer census data and carcass counts. From the fall of 1957 to the fall of 1961, deer populations increased from 16.9 ? 2.7 deer per 100 acres to 26.1 ? 3.7. The 1962 census, following the die-off, was 14.6 ? 2.1 deer per 100 acres-a reduction of approximately 44 percent, of which some 30,000 were lost in the die-off. The deer herd responded to lowered population pressures with a higher reproductive rate, and the 1963 deer census showed a population of 26.7 ? 3.7 deer per 100 acres. Searches of 30, 128-acre plots (3,840 acres) for carcasses revealed a loss of 7.3 1.7 deer per 100 acres (20,000-31,000 deer). This agreed closely with mortality losses estimated from census counts. Deer harvests, though the highest reported for North America, were inadequate. Deer lost in this die-off approximated the legal kill during the preceding three seasons combined. Antlerless deer harvest was reduced following the die-off. Since population recovery occurred in 1 year, hunting pressure on antlerless deer should have been maintained in the face of natural herd, reduction to hold deer populations at an acceptable level. Die-offs have played an important role in the management and production of most established North American deer herds. The causes of reported die-offs have varied, with the primary cause usually suspected to be overpopulation resulting in malnutrition with its various side effects. Detailed reports of the causes and extent of these die-offs are rare in the literature. This paper reports a die-off following heavy overpopulation and range abuse. Deer mortality checks were supervised by Jerry L. Butler and H. M. Otto. Albert W. Jackson performed much of the statistical treatment of the data, supervised the remainder, and encouraged the preparation of the paper for publication. The manuscript was carefully edited by Dan W. Lay and Drs. R. B. Davis, R. M. Robinson, and James G. Teer. We gratefully acknowledge these contributions. REVIEW OF LITERATURE North America excluding Texas Die-offs of black-tailed deer and mule deer (Odocoileus hemionus) due to overpopulation and malnutrition have been reported (Klein and Olson 1960, Dasmann 1956, Rasmussen 1941). State and federal records indicate that approximately 50 major white-tailed deer die-offs have occurred in the southeastern United States from 1890 to 1958 (Hayes et al. 1958). Whitlock and Eberhardt (1956:560) reported a loss of about 32,500 deer in Michigan to starvation, crippling loss, and illegal doe and fawn shooting during the winter of 1954-55. Sudden, significant deer losses attributed to epizootics have been reported in Michigan (Fay et al. 1956), in New Jersey (Shope et al. 1955, 1960) and in North Carolina (Ruff 1960). Migratory white-tailed deer herds in New York have been reported to live on 70 square miles during the summer and congregate on 8-14 square miles in the 1 This study is a contribution of Texas PittmanRobertson Project W-62-R.

PRONGHORN DIE-OFF IN TRANS-PECOS TEXAS'

Pronghorn antelope (Antilocapra americana) numbers on the Marfa Flat, comprising 75,000 acres in Presidio County, Texas, declined from 484 in June, 1964, to 148 in June, 1965. Nearly 60 percent (274) of the original number died from causes other than hunting. Pronghorns were confined on this area by net-wire fences. Three years of below-average rainfall combined with heavy stocking of cattle, horses, and pronghorns caused severe range depletion and forced pronghorns to rely almost entirely on browse species for sustenance. Only tarbush (Flourensia cernua), creosotebush (Larrea divaricata), and snakeweed (Amphiachyris dracunculoides) were readily available. Twelve pronghorns were observed to be utilizing a diet composed almost entirely of tarbush during the winter and spring period. Lesions characteristic of tarbush toxicity were found in 83 percent of the animals examined. Resorbing embryos were found in three of four females that had conceived. Malnutrition coupled with tarbush toxicity was considered to be the cause of the losses. Reproductive rates were reduced from 52 fawns per 100 does in June, 1964, to 17 fawns per 100 does in June, 1965. Pronghorns on ranches with a variety of more desirable browse species suffered only minor losses. Adjustment of stocking rates to forage available, construction of fences allowing pronghorn movement during periods of food shortage, and the possibility of limited, temporary supplemental feeding are management practices that might prevent the recurrence of such losses.

Fecal nitrogen and dietary quality relationships in juvenile elk

Dietary quality influences growth and condition of juvenile ruminants. Fecal nitrogen potentially provides a noninvasive measure of dietary quality, but fecal nitrogen-dietary relationships in juvenile ruminants are unknown. We used 6 hand-reared juvenile elk (Cervus elaphus) to investigate relationships between fecal nitrogen and milk intake, solid food intake, and nutrient content of solid food during the first 6 months of life. Fecal nitrogen declined from 4.2%, before consumption of solid food began, to 2.2% when solid food made up 80% of total daily intake in late summer. Fecal nitrogen was not related (P > 0.05) to milk consumption in calves consuming only milk

FROM MANAGING A DEER HERD TO MOVING A MOUNTAIN-ONE PILGRIM'S PROGRESS

The profession of wildlife management has developed rapidly, philosophically and technically, from attention to the study and management of select game species to leadership in such ventures as ecosystem management. The story of important milestones along this journey is told through the personal story of one

INFLUENCE OF FORESTLAND CHARACTERISTICS ON SPATIAL DISTRIBUTION OF HUNTERS

To determine the effects of 17 access, cover, relief, and game variables, we interviewed hunters as they left a 9,500-ha area of national forest and private land in West Virginia. Hunters were classed as hunting for deer (Odocoileus virginianus), turkeys (Meleagris gallopavo), or squirrels (Sciurus carolinen- sis, S. niger). The area was divided into 166 blocks of 64.8 ha or less, and each block was rated on the 17 variables. The number of hunters that visited a block decreased with distance from a trail, camping or parking site, road, or wildlife clearing, and with decreases in length of public land boundary and amount of game seen. In regressions of data from 3 years, all variables accounted for 33 to 44 percent of the variation in visits to the blocks and the 6 most important variables accounted for 26 to 30 percent. These were trails (all hunters), camping or parking sites (deer and turkey), wildlife clearings (turkey), pub- lic boundary, roads, and game seen (squirrel hunters). Proximity of trails accounted for much more vari- ation in hunter visits than cover type did, but game distribution related more to cover type than to trails. Hunter-game contact could be increased least expensively by trail management. The findings suggest limits of the effectiveness of management alternatives, and that hunters were influenced by factors other than site characteristics and game-seeking efficiency.