James A. Bailey

CAPABILITY OF MULE DEER TO UTILIZE FIBROUS ALFALFA DIETS

Two 14-day feeding trials were conducted to compare abilities of mule deer (Odocoileus he- mionus), domestic sheep (Ovis sp.), and goats (Capra sp.) to digest a poor-quality, high-fiber alfalfa diet fed in pelleted and cubed forms. Six of eight deer fed pelleted alfalfa and five of eight fed cubed alfalfa experienced digestive problems. Four domestic sheep and four goats fed these rations did not evidence any problems. Two of the deer fed pellets and four of the deer fed cubes experienced severe digestive upsets and were sacrificed when near death. Necropsy revealed extensive hemorrhagic ulcera- tions within the abomasa and small intestines of all deer. Two of the deer, both fed cubes, also had greatly distended omasa due to food impaction. Food particles in stomach contents from deer that experienced digestive problems were significantly larger than particles in stomach contents from sheep, goats, or deer that did not evidence digestive problems. Comparison of stomachs among deer, sheep, and goats indicates major size differences. Related to body size, deer have smaller rumen- reticula, omasa, and abomasa than either sheep or goats. The smaller digestive organs in deer suggest they require more nutritious, easily digested forages than do sheep or goats.

Experiments on Starvation and Recovery of Mule Deer Does

We attempted to test the hypothesis that mule deer (Odocoileus hemionus) subjected to a short period of starvation would exhibit better survival after feeding than deer starved presumably nearly to death. But, no starved deer died after feeding resumed. We were unable to synchronize condition of starving deer to produce a group close to death at resumption of feeding. Free-ranging deer starving in winter probably also lack synchrony of declining physical condition. We therefore postulate that supplemental feeding can save a portion of the herd not already close to death. Comparison of blood parameters for nonstarved deer, starved deer, and deer dying of starvation for two trials indicated that: (1) deer catabolize stored fat and muscle protein during starvation, and (2) increased catabolism of muscle protein as fat stores are depleted results in impaired gluconeogenesis and deer in this hypoglycemic state succumb to starvation. J. WILDL. MANAGE. 41(1):81-86 Studies involving feeding of starved penned mule deer (deCalesta et al. 1974, 1975) did not confirm three hypotheses concerning failure of winter feeding to prevent losses. These were: (1) rumen microorganisms of starving deer are lost, die, or lose the ability to digest feeds; (2) chemical composition of feed fed to starving deer influences survival; and (3) deer become irreversibly moribund when starved longer than a certain period and cannot be saved by feeding. Our data suggested that starved deer dying after new food was offered were already dying when feeding commenced and had not died as a result of feeding. Success of feeding starving deer probably depends on the degree to which metabolic changes progressed prior to feeding. The purpose of this research was to test the hypothesis that deer subjected to a short period of starvation would exhibit better survival after feeding than deer subjected to starvation of sufficient duration to render them close to death. We thank R. W. Phillips, Department of Physiology and Biophysics, Colorado State University, for his advice and the use of his laboratory, and V. Athanasiou, T. Bahti, G. Collins, A. Jones, M. Loftsgard, D. Reeder, D. Roy, G. Schoonveld, W. Vassar, and L. Young for assistance with laboratory analysis and animal handling. Financial aid and pen space were provided by the Colorado Division of Wildlife Resources (P-R Proje t W-38-R-24) in cooperation with the U.S. Fish and Wildlife Service.

Exploratory study of nutrition of young cottontails.

Domestic grasses and legumes, and wild forbs were tested in feeding and digestion trials with young cottontails (Sylvilagus floridanus) during spring, summer, and autumn. Grasses were the poorest foods in all seasons and were particularly indigestible during summer. Legumes were generally better foods than grasses, but their nutritive value likewise declined as the plants matured in summer. Among eight species of wild forbs, four were excellent foods during at least one of the three seasons. It is concluded that young cottontails require highly digestible food which can be provided by palatable plants in vigorous growth stages. In habitats managed for cottontails, adequate nutrition of young rabbits can be assured by establishing polytypic stands of wild forbs, the variety of species in such stands providing some plants in a stage of vigorous growth throughout the growing season. The objective of this research was to measure the nutritive values of certain grasses, legumes, and wild forbs to young cottontails during spring, summer, and au-

Trap Responses of Wild Cottontails

Effects of weather, season, sex, and age upon the trap responses of wild cottontails (Sylvilagus floridanus) were evaluated using data obtained from September through March in two trapping seasons. Except for adult males, rabbits became more trappable during weather conditions prevailing when barometric pressure was high. Adult males became more trappable during weather including precipitation. Overall, 13 percent of the variation in trap success was associated with weather factors. Although female rabbits were more trappable than males, the difference was not statistically significant. Rabbits were most trappable at the age of 4-5 months and thereafter became less trappable, especially as adults. A uniform probability of capture did not exist among individuals within sex-age classes. The animals were most trappable during October through December, less trappable during September and January, still less trappable during February, and least trappable during March. Statistical models including sex, age, and month accounted for about 20 percent of the variation among trap responses. Trap success cannot be a sensitive index to population density and sex-age structures of trapped samples will usually be biased toward overestimation of the proportions of juveniles and females in rabbit populations. Studies of wild populations of cottontails often include periodic trapping with box traps. Analyzing the resulting data usually involves the questionable assumptions that trapped animals are randomly drawn from the population and that success in trapping can be used as an index to population density. Geis (1955) demonstrated that individuals within rabbit populations were not 1A contribution from Federal Aid Project W-66-R, the Illinois Department of Conservation, the U. S. Bureau of Sport Fisheries and Wildlife, and the Illinois Natural History Survey, cooperating. 2 Present address: School of Forestry, University of Montana, Missoula, 59801. equally trappable, and the aggregate of several other studies, mentioned below, has suggested that variation among trap responses of rabbits is associated with weather, season, the sexes and ages of the animals, habitat, the density of the rabbit population, and the number and distribution of traps. Effects of the first three fact rs upon trap responses of cottontails are

Quantity of soft pellets produced by caged cottontails.

Production of the soft pellets that cottontails (Sylvilagus floridanus) normally reingest was measured with caged adults on commercial rabbit food. Soft pellets amounted to 30.4 percent of the total weight of both hard and soft pellets, a result similar to those reported for domestic rabbits (Orycto!agus cuniculus ). Production of soft food pellets (as opposed to hard fecal pellets) by caged adult cottontails on a diet of commercial rabbit food and water was measured during March 27-31 and June 20-23, 1967. All animals had been captive indoors in individual 16x 24x 13-inch wire cages for at least 18 weeks before the tests began. Production of food pellets was measured for six rabbits during each period. However, three animals were involved in both tests. Thus, nine animals were involved in the 12 determinations of food-pellet production. The animals were fitted with cardboard collars, 10 inches in diameter, which prohibited reingestion of soft pellets. Hard and soft pellets were collected from under the cages three times each day, beginning on the day after the collars had been fitted. Soft pellets were identified by their shape and their glutinous, textureless appearance. All pellets were dried at 65 C and weighed. Production of soft pellets was expressed as a percent of the total weight of both hard and soft pellets. Averages of production of soft food pellets by six cottontails during the March and June tests were 29.3 and 31.5 percent of total pellets, respectively. Since these averages were not significantly different, data for the two tests were combined; the aver1 A contribution from Illinois Federal Aid Project W-66-R, the Illinois Department of Conservation, the U. S. Bureau of Sport Fisheries and Wildlife, and the Illinois Natural History Survey, cooperating. The suggestions of G. C. Sanderson, W. R. Edwards, and Helen C. Schultz are acknowledged. 2 Present address: School of Forestry, University of Montana, Missoula, 59801. age production of food pellets for 12 determinations was 30.4 percent, with confidence limits between 26.2 and 34.6 percent (P < 0.05). In similar studies with domestic rabbits, Kulwich et al. (1953) and Huang et al. (1954) determined that 26.4 percent and 26.8 percent of the total pellets were food pellets, respectively. These averages are within the confidence limits mentioned above for cottontails. Six of these cottontails also participated in digestion trials during January, 1967, wherein the average digestibility of dry matter in Purina Rabbit Chow was 67 percent (range = 6271 percent). This was comparable to a coefficient of 68 percent obtained with domestic rabbits (Voris et al. 1940). Reingestion provides for a more complete digestion of the rabbits food. Using the above digestion coefficient for cottontails and the information that food pellets amount to 30 percent of total pellets, it is calculated that with reingestion prohibited, the digestibility of Rabbit Chow would have been 53 rather than 67 percent.