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Nieświszcze, Cynomys ludovicianus (Ord, 1817), wystepują licznie na preriach amerykanskich na wschod od Gor Skalistych, od poludniowej Kanady az po Meksyk. Na pastwiskach mogą one konkurowac z bydlem domowym, poniewaz odzywiają sie tymi samymi roślinami. Na 20 dorastających nieświszczach, w ciągu trzech miesiecy wykonano 4 kolejne serie doświadczen zywieniowych, z ktorych kazda trwala 15-18 dni. Zwierzeta trzymano dwojkami w klatkach metabolicznych, karmiono je standardową paszą (Tabela 1), określano dokladnie konsumpcje i fekalia.

On caracterise la vegetation et les sols des Terriers abandonnes de Cynomys ludovicianus et utilises pour nidifier par Athene cunicularia et on les compare avec ceux des terriers non occupes par l'oiseau

daily gains appear to have been limited by the ability of the steers to consume enough forage. Had the available forage been of higher quality, increased rates of gain would undoubtedly have occurred since the forage was available. It appears that intake capacity of this size steer limits live weight gains on a deep hardland range site. For increased live weight gain, additional protein and energy would need to be provided as a supplement to the forage. When supplementation is economically infeasible, these data indicate that only about .45 kg/head daily gain can be expected from yearling steers grazing similar Texas High Plains range. Literature Cited

The botanical composition of herbage consumed by domestic sheep, mule deer, domestic cattle and elk from critical big game winter ranges in southcentral Colorado was studied using the fecal analysis technique. The food habits of domestic sheep grazed during the late spring overlapped those of mule deer by 15%, elk 46%, and domestic cattle by 53%. Mule deer diets were 10% similar to cattle and 30% to elk. Elk and cattle diets averaged 39% identical on the study area. The low similarity in diet between domestic stock and mule elk suggests that livestock grazing in the study area could be made compatible with the winter range needs of mule deer, but the potential competition between elk and domestic stock needs additional study. Late spring grazing by domestic sheep (i Cook et al. 1962; Van Dyne and Meyer 1964; Wilson et al. 1971; and Olsen and Hansen 1977). However, perusal of the literature over the past three decades clearly indicates that much more is known about the food habits of big game animals on Colorado rangelands than is known about domestic animal food habits on the same lands. The purpose of this paper is to provide information about domestic sheep diets in relation to those of mule deer, domestic cattle (Bos taurus) and elk (Cervus canadensis) on big game winter ranges which may be critical to the successful overwintering of mule deer and elk. An objective was to estimate whether the recent past use of the study areas was resulting in excessive dietary overlaps. Study Area and Procedures The study area was located on the big game winter range of the Alamosa District, Rio Grande National Forest in the San Juan mountains of southcentral Colorado. The study area extends approximately 8 kilometers west of the forest boundary and the mean elevation is 2,833 m ranging from 2,589 m to 3,000 m. The vegetation pattern was uniform throughout the area and three basic plant communities could be distinguished. On the more xeric sites a mixture of shrub steppe and pinyon-juniper vegetation types were found. The major plant species of the shrub steppe were rubber rabbitbrush (Chrysothamnus nauseosus), big sagebrush Authors are graduate research assistant and professor, respectively, Range Science Department, Colorado State University, Fort Collins 80523. We would like to thank J.E. Sazama for his help in organizing the study and T.M. Foppe who performed the analysis of fecal samples. This study was supported in part by the U.S. Forest Service Wildlife Internship Program. 242 (Artemisia tridentata), broom snakeweed (Gutierrezia sarothrae), fringed sagewort (Artemisia frigida), blue grama (Bouteloua gracilis), western wheatgrass (Agropyron smithii), bluegrass (Poa spp.), Arizona fescue (Festuca arizonica), carices (Carex spp.) and needleandthread grass (Stipa comata). The pinyon-juniper type contained pinyon pine (Pinus eduhs), juniper (Juniperus spp.), true mountainmahogany (Cercocarpus montanus), currant (Ribes spp.), fringed sagewort, blue grama, and carices. The major plant species found on mesic sites were ponderosa pine (Pinus ponderosa), douglas fir (Pseudotsuga menziesii), quaking aspen (Populus tremuloides), rose (Rosa spp.), currants, thurber fescue (Festuca thurberi), Arizona fescue, brome (Bromus spp.), prairie junegrass (Koeleria cristata), bluegrass, and carices. Plant names follow those recommended by Beetle (1970). Domestic sheep were released on the study areas in late spring and were herded to higher elevations as the snow melted. Domestic cattle use was heaviest in early summer and progressively decreased as the summer advanced and by late summer most of the cattle had moved to higher elevation ranges. Mule deer and elk typically arrived on the study area in late fall and early winter and remained until late March. In winters with more than average snowfall, they may remain until April or early May. The botanical composition of sheep, cattle, deer, and elk feces was determined by microhistological examination as described by Sparks and Malecheck (1968). Fecal samples were collected from two areas on the winter range during the summer after domestic stock had used the aeas. Each area was approximately one square kilometer in size and was located along the common border of a sheep and cattle allotment. Samples for each herbivore species were derived from 50 single defecations located at random throughout the area. Each subsample was about one cubic centimeter of fecal material. Five microscope slides were made from each sample and 20 fields were examined per microscope slide at 100X magnification. Diet similarity between species of herbivores was calculated using Kulcyznski’s similarity index (Oosting 1956). Results and Discussion The major components of the diet selected by sheep were grasses and sedges (Table 1). Western wheatgrass, blue grama, carices, and Table 1. (Mean &SD) percent relative density of plant fragments in fecal samples of four ungulates in southcentral Colorado from low elevation winter range of big-game. Plant species* Sheep Cattle Deer Elk Agropyron smithii 36 f 5 29 f 27 If 1 14fll Bouteloua gracilis 18f 2 5f 6 If 1 Carex spp. 15f7 4Of35 3f 1 17f 2 Koeleria cristata 9f3 9f 1 2f 2 8f 1 Festuca spp. If1 6f 2 2f 1 14f 17 Artemisia spp. 7f3 1 f 1 16f 2 23f 12 Cercocarpus montanus 12f 2 If 1 Juniperus spp. 10f 6 Pinus edulis 28 f 14 Psuedotsuga menziesii 13f 9 6f 3 *Other taxa in the diets were Aristida, Blepharoneuron, Muhlenbergia. Oryropsis, Pea. Sitanion. Stipa, Ceratoides, Berberis. Chrysothamnus, Descurainia, Eriogonum. Fragaria, Lupinus. Penstemon, Picea. Purshia, Ribes, Rosa, Sheperdia. Sphaeralcea, Symphoricarpos. Yucca and Potentilla in small (

Highlight: Spring population densities of black-tailed jackrabbits, white-tailed jackrabbits, and desert cottontail rabbits were estimated on pastures under four different grazing treatments by cattle on the shortgrass prairie of northeastern Colorado. Black-tailed jackrabbits were most abundant on pastures with light-summer and moderate-summer grazing treatments. White-tailed jackrabbits showed no strict preference for any grazing treatments but preferred all upland pastures. Desert cottontail rabbits were most abundant in pastures under moderate-summer and moderate-winter grazing treatment. The ratio of abundance between the three species of leporids is, in part, a function of the different levels of grazing intensity. A ny future long-term changes in vegetational management in the area could be expected to affect populational ratios.

Agr., Bur. Plant Ind. Bull. 74. 46 p. Griffiths, D. 1912. The thornless prickly pears. U.S. Dep. Agr., Farmers Bull. 483. 20 p. Healy, W. B. 1973. Nutritional aspects of soil ingestion by grazing animals. p. 567-588. In: G. W. Butler and R. W. Baily (Ed.). Chemistry and biochemistry of herbage. Vol. 1. Academic Press, New York. Hoffman, G. D., and R. A. Darrow. 1955. Pricklypear, good or bad? Texas Agr. Exp. Sta. Bull. 806. 12 p. Karns, W. J. 1952. Cowboys with blowtorches. Compressed Air Magazine 57:190-193. Maynard, L. A., and J. K. Loosli. 1969. Animal nutrition. 6th ed. McGrawHill Book Company, New York. 613 p. National Research Council (NRC). 1970. Nutrient requirements of domestic animals. No. 4 Nutrient requirements of beef cattle. 4th revised ed. Nat. Res. Counc., Washington, D.C. 55 p. Pinney, D. O., D. F. Stephens, and L. S. Pope. 1972. Lifetime effects of winter supplemental feed level and age at first parturition on range beef cows. J. Anim. Sci. 34:1067-1074. Shoop, M. C., and D. N. Hyder. 1976. Growth of replacement heifers on shortgrass ranges of Colorado. J. Range Manage. 29:4-8. Tflley, J. M. A., and R. A. Terry. 1963. A two-stage technique for in vitro digestion of forage crops. J. Brit. Grassland Soc. 18:104-111. Van Dyne, G. M. 1962. Micro-methods for nutritive evaluation of range forages. J. Range Manage. 15:303-313. Van Soest, P. J. 1965. Use of detergents in analysis of fibrous feeds. III. Study of effects of heating and drying on yield of fiber and lignin in forages. J. Ass. Offic. Chem. 48:785-790. Van Soest, P. J. 1967. Development of a comprehensive system of feed analyses and its application to forages. J. Anim. Sci. 26:119-127. Van Soest, P. J., and R. H. Wine. 1967. Use of detergents in the analysis of fibrous feeds. IV. Determination of plant cell wall constituents. J. Ass. Offic. Agr. Chem. 50:50-55. Wiltbank, J. N. 1972. Management of heifer replacements and the brood cow herd through the calving and breeding periods, p. 150-187. In: C. C. O'Mary and I. H. Dyer (Ed.), Commercial beef cattle production. Lea and Febiger, Philadelphia, Pa. Woodward, T. E., W. F. Turner, and D. Griffiths. 1915. Pricklypearas feed for dairy cows. J. Agr. Res. 4:405-450.

Vegetation, small rodents, and birds were sampled during the growing seasons of 2 years on prairie dog (Cynomys ludovicianus) colonies and adjacent mixed-grass prairie in western South Dakota. Prairie dog grazing decreased mulch cover, maximum height of vegetation, plant species richness, and tended to decrease live plant canopy cover compared to that on ungrazed mixed-grass prairie. Buffalograss @~~&educry~of&s) was the dominant plant on prairie dog towns and western wheatgrass (Agropyron smithii) and blue grama (Boutelouugrucilis) were most common on mixedgrass prairie sites. Prairie dog towns supported greater densities of small rodents but significantly fewer species compared to undisturbed mixed-grass sites. Deer mice (Peromyscus maniculatus) and northern grasshopper mice (Onychomys leucogaster) were more abundant on prairie dog towns than on undisturbed mixedgrass sites. Density and species richness of birds were significantly greater on prairie dog towns. Horned larks (Eremophila a&es&i@ were most common on prairie dog towns, whereas western meadowhuks (Sturneihz neglecta) were most common on mixed-grass prairie.

The number of free-roaming horses has been increasing in the West in recent years (Cook, 1975). Wherever there is a need to manage horses on National Resource Lands it is necessary to determine their food habits to prevent the destruction of plant cover and to maintain maximum herbage production. The objective of this paper was to report the seasonal foods of a group of free-roaming horses which lived on the White Sands Missile Range in southern New Mexico.

Highlight: The trophic relations among blacktail prairie dogs, desert cottontails, and cattle were determined among three dogtowns at the Central Plains Experimental Range near Nunn, Colo. Sedges were the most important food of prairie dogs and cottontails and the second most important food of cattle on an annual basis. There was a high percentage similarity in the diets of the three herbivores studied; and they cDnsumed large percentages of sedges and grass. The amount of aboveground herbage eaten and made unavailable because of soil disturbances by prairie dogs and cottontails was about 24% of the total potential annual production.

Inadequate data have existed concerning cattle preferences for fourwing saltbush [Atriplex canescens (Pursh) Nutt.] on ranges where it is dominant, and concerning composition of cattle diets on the central shortgrass plains. In this study, food habits of cattle were estimated from fecal analyses on winter and summer pastures containing either abundant or sparse fourwing saltbush (saltbush). The abundant saltbush was on overflow and/or sandy plains range sites; sparse saltbush was on loamy plains range sites. Saltbush was a major constituent of cattle diets where abundant. The proportion of saltbush in winter diets peaked during March (55%) and declined during April. Saltbush was absent from summer diets during July, peaked during August (42%), and declined abruptly during September. Where abundant, saltbush was also the primary constituent of the forb-shrub component of diets during both winter (X=72%) and summer (X=44%). Deleting saltbush from the data, cattle foods consumed on pastures with sparse and abundant saltbush were correlated (0.84) during summer, but were not correlated (0.25) during winter. Relative to species frequencies in pastures, cattle diets on loamy plains range sites (sparse saltbush) contained notably larger portions of sedges (Carex spp. L.), goosefoots (Chenopodium spp. L.), and fringed sagewort (Artemisia frigida Willd.), during winter and goosefoots and scarlet globemallow [Sphaeralcea coccinea (Nutt.) Rydb.] during summer, than diets on sandy plains and overflow sites (abundant saltbush). Saltbush is a preferred and valuable forage for cattle on the central shortgrass plains, and it should be managed to maintain or improves its productivity. Fourwing saltbush [Atriplex canescens (Pursh) Nutt.] is one of the most widely distributed, highly palatable, and nutritious browse species in the western United States (Bidwell and Wooten 1925, Plummer et al. 1966, Pieper and Donart 1978). However, little quantitative data exist pertaining to cattle diets in areas where fourwing saltbush (saltbush) is abundant. Cattle dietary habits are complex, and are affected primarily by relative availability and palatability of foods. Traditionally, cattle have been classified as general grazers, primarily ingesting grasses while utilizing forbs and browse only occasionally or in stress situations (Cook et al. 1967, Lesperance et al. 1970, Allison et al. 1977). A number of cattle dietary studies have emphasized the importance and potential of certain forb and browse species as cattle foods (Cully 1937, Herbel and Nelson 1966, Thetford et. al. 1971, Rosiere et al. 1975, Vavra et al. 1977). Saltbush provides relatively large amounts of essential nutrients, including protein, phosphorus, calcium, and carotene, even during winter months (Bidwell and Wooten 1925, Watkins 1943, Cook and Harris 1968, Pieper et al. 1959, Sims and Taylor 1973, Cordova and Wallace 1975, Cook et al. 1977). The digestibility of saltbush often compares favorably with that of grasses, forbs, and At the time of research, Shoop and Laycock were range scientists, USDA, ARS, Forage, Range, and Livestock Management Investigations, Crops Research Laboratory, Colorado State University, Fort Collins 80523; Clark and Hansen were research associate and professor, respectively, Department of Range Science, Colorado State University, Fort Collins 80523. The current address of Clark is 532 University Ave., Boulder, Colo. 80302. This article is the result of cooperative investigations of the USDA, Agricultural Research Service, and Colorado State University. Experiment Station. Colorado State University Scientific Series Paper No. 2870. Manuscript accepted January 28, 1985. other shrubs (Pieper et al. 1959, Cook and Harris 1968, Sims and Taylor 1973, Cordova and Wallace 1975), but its digestibility during dormancy may not compare well with that of grasses under some situations (Sims and Taylor 1973). On ranges where abundant, saltbush should ameliorate forage shortages, e.g., during droughts and snow covers (Foster et al. 1921, Plummer et al. 1966, Pieper and Donart 1978). By adding species diversity, saltbush should improve the quality of cattle diets (Herbel and Nelson 1966, Plummer et al. 1966, Cook and Harris 1968, Pieper and Donart 1978). Saltbush has other noteworthy attributes. It provides a microenvironment where other species can produce more herbage and protein and can become established and survive more successfully than in its absence (Monsen 1980, Rumbaugh et al. 1982, Laycock and Shoop unpublished data). Fairchild and Brotherson (1980) reported greater levels of some minerals beneath saltbush plants than between them. Saltbush has been reported as a secondary or facultative selenium accumulator (Fleming 1920), and perhaps it could accumulate toxic levels of selenium from depths below roots of associated species (Foster et al. 1921). Data are lacking or inadequate for cattle dietary preferences on shortgrass range in the Central Plains relative to winter-use, sandy plains or overflow range sites, summerlong grazing, or moderately grazed pastures. The most comprehensive of the earlier studies reported esophageal and fecal data collected during June through August of 2 years and December of 1 year from heavily and lightly grazed summer pastures at the Central Plains Experimental Range (CPER) (Rice and Vavra 1970, Vavra et al. 1977, Vavra et al. 1978). These studies were conducted in pastures primarily on a loamy plains site, but that included a small, plains swale site that produced considerable western wheatgrass (See Table 1 for Latin names of species). Kautz and Van Dyne (1978) used the foregoing studies and a limited amount of associated data to report mean percentage consumption of each species detected in diet samples. Hansen and Gold (1977) reported mean seasonal dietary composition of a limited number of species at CPER as determined from fecal samples collected intermittently from various range sites, some of which included revegetated abandoned cropland. Quinton (1972) reported 2 years of data for 6 plant species and categories on 2 pastures on a loamy plains range site near Akron, Colo. The primary objective of this study was to determine the importance of saltbush relative to other forages in the diets of cattle on winter and summer pastures on the central shortgrass plains. A secondary objective was to help characterize cattle diets on the shortgrass range of northcentral Colorado, especially for winter pastures and summer pastures on sandy plains range sites.

The botanical composition of the diets of domestic cattle and mule deer (Odocoileus hemionus) was estimated by microscopically examining fecal samples collected on deer winter ranges heavily used by cattle. Diet overlap ranged from 1 to 22% (‘x = 12%) on the nine areas studied. When cattle are forced from a grass dominated diet to browse forage on overgrazed ranges, diet overlap and therefore forage competition increases between deer and cattle. The effects of excessive livestock use on the winter range of mule deer continues to be controversial in the Rocky Mountain Region, especially since less than 50% as many deer are harvested now as were 20 years ago. Recent literature suggests that diet overlap of domestic cattle and mule deer in northwestern Colorao was about 4% in 1975 (Hubbard and Hansen 1976; Hansen and Clark 1977; Hansen et al. 1977). Many wildlife biologists believe dietary overlap between mule deer and cattle should be much higher and some literature published 20 to 40 years ago supports this contention (Robinson 1931, 1973; Interstate Deer Herd Committee 1947). An objective of this study was to select mule deer wintering sites which appeared to have been continuously abused by livestock for many years, and to determine early winter foods selected by mule deer and cattle on these same sites. We hypothesized that in these extreme cases, diet overlap would be higher than on ranges in better condition.

Although there have been several reports on the food h-abits of domestic herbivores in various semiarid regions of the world, there has been no previous report on the partitioning of forage resources by camels (Camelus dromedarius) and sheep (Ovis aries,), goats (Capra hircus) and cattle (Bos indicus) using a common rainge. In the semiarid region of northern Kenya, the seasonal exploitation by these herbivores resulting from herding by the nomadic Rendille pastoralists makes the system for management of these rangelands very complex. Information on the food habits of inimals utilizing a common range is important in offering a biasis for assessing the usefulness of the range components to the animals. Consequently, food habits information becomes an important tool in making management decisions. Camels were predominantly browsers while cattle were predominantly grazers. Sheep aind goats were intermediate feeders. Cattle browsed most during the! 'green' season when the browse shoots were most abundant and easiest for their large mouth parts to harvest. Camels grazed most duiring the very dry season when most trees and shrubs had shed their leaves. The observed variations in food habits among the 4 herbivores suggest that they may require different management to obtain optimum production.

Local meteorological conditions appear to influence the periodicity of Townsend ground squirrels ( Citellus townsendii ). On June 5, 1951, young Townsend ground squirrels from Stansbury Island, Great Salt Lake, Utah, were found to be almost adult in size. Those on the surrounding mainland at this time were smaller sized and appeared to be younger. On April 22, 1952, young Townsend ground squirrels …

Three hybrid short-tailed ground squirrels have been reported from Western United States. The first was identified as a cross between Citellus annatus and Citellus beldingi (Davis, W. B., the recent mammals of idaho, Caxton Printers, Caldwell, Idaho, 1939: 169). The other two were identified as … “hybrids or may be intergrades” … between Citellus armatus and Citellus richardsoni (Hall, Amer. Midl. Nat., 29: 378, 1943). The studies of Durrant and Hansen (Systematic Zool., 3: 82–85, 1954) on competition between species of short-tailed ground squirrels (Subgenus Citellus ) show that animals of different species never hybridize. Moreover, at the zone of contact between colonies of any two species, the competition is extreme; the burrows and feeding areas of the animals of one species being in some instances but a few feet from those of the other species. I have collected a number of specimens from areas where the ranges of C. armatus overlap those of C. richardsoni and C. beldingi and have found no indication of interbreeding. In addition, I studied several hundred museum specimens of these species and found no indications of interbreeding. This prompted me to re-study the “supposed” hybrids that had been previously reported. Plate 1 X-ray photograph of the dentary bones and extra incisor of a varying lemming that died when 69 days old. I thank Dr. S. D. Durrant, Museum of Zoology, University of Utah, Salt Lake City, Utah, for his supervision and suggestions during the course of this study, and for allowing me to examine the specimens in the University of Utah collection.I also thank Dr. Seth B. Benson, Museum of Vertebrate Zoology, University of California, Berkeley, California, for examining the field notes and museum records pertaining to the specimens suspected to be hybrids, and …

In Utah, precise data are lacking concerning population fluctuations of most members of the genus Citellus . In the years preceding 1936, Townsend ground squirrels ( Citellus townsendii ) were common throughout central Utah and the West Desert. They were particularly abundant south and west of Utah Lake, Cedar Valley, Rush Valley, Tintic Valley and Nephi Valley. They were the most conspicuous mammal observed while traveling the uncultivated part of the West Desert. During the early part of the summer of 1936, these animals were as numerous as the preceding years. In mid-summer, there occurred an epizootic. The …

Many kinds of mammals reach their distributional limits in Utah. This is especially true of rodents restricted to montane or desert habitats. The diverse topography has been instrumental in developing many isolated or semi-isolated populations that have subsequently evolved into recognizable kinds. The central mountain ranges, beginning in northern and northeastern Utah, extend in a southern and southwestern direction. These mountains separate the deserts of the Lake Bonneville Basin from those of the Colorado Drainages of southern, southeastern and eastern Utah. Correspondingly, the desert areas in which antelope ground squirrels occur are also separated. In eastern and southeastern Utah, the Green and Colorado rivers, and their tributaries, with their deeply entrenched canyons, are also barriers that restrict gene flow between populations of antelope ground squirrels. In attempting to re-evaluate the effects of river systems and mountain barriers on the evolution and subspeciation of antelope ground squirrels in Utah, two populations were found that were beyond the range of variation found in the already known subspecies. These are here described as new subspecies. Acknowledgements .—I wish to thank Dr. Stephen D. Durrant of the University of Utah for his supervision and helpful suggestions; the United States Public Health Service, Microbiological Institute for financial aid during the course of this study; the following persons and institutions for the loan of specimens: John Aldrich and Viola S. Schantz, U. S. National Museum, Washington D. C.; J. Kenneth Doutt and Caroline A. Heppenstall, Carnegie Museum, Pittsburgh, Pennsylvania; Seth B. Benson, Museum of Vertebrate Zoology, University of California, Berkeley, California; Vasco M. Tanner and C. Lynn Hayward, Brigham Young University, Provo, Utah; Howard Knight, Weber Junior College, Ogden, Utah. Methods .—Comparisons are of adult specimens unless otherwise indicated. Color comparisons are of summer pelage unless otherwise stated. Capitalized color terms are those of Ridgway (color …

Most authors agree that a female deer mouse with a young litter does not tolerate the presence of other adults in the same nest with her young (Dice, Jour. Mamm., 10: 116–124, 1929; Svihla, Misc. Publ. Mus. Zool. Univ. Mich., 24, 1932; Blair, Jour. Mamm., 22: 378–383, 1941). It is therefore worthy to record the finding of two females and eleven young occupying the same nest under natural conditions. On May 8, 1956, at the Seyfang Ranch, …

The importance of lemmings in the arctic and subarctic regions has long been recognized, but there is little known about their ecology. The cause of cyclic populations in these animals remains unknown. In all of the studies so far recorded, the die-off has been in the winter or early spring following a population peak. At this time (in late winter) the length of daylight begins to increase, and it has been postulated that the increased light stimulates most mammals into sexual activity (Christian, 1950). This has not been demonstrated in the varying lemming, and furthermore, these animals are reproductively active at all periods of the year (Degerbol and Mohl-Hansen, 1943; Manning, 1954; Ross, 1835; Sutton and Hamilton, 1932). Elton (1942) indicated that intraspecific factors may be the primary causes of population fluctuations. Errington (1946) included “fighting” as one of the intraspecific mechanisms which he believed basically determined population levels. Chitty (1952) puts forth the hypothesis that fighting produces physiological changes in parents which give rise to abnormalities in the young. Clark (1953) showed the effects of fighting on the adrenals, thymus and spleen of the vole Microtus agrestis , and stated that it produced a “weakened” condition in voles. Since fighting is a part (or result) of activity, it was deemed desirable to study the activity of varying lemmings, Dicrostonyx groenlandicus rubricatus (Richardson), in relation to increased daylengths. Moreover, most intraspecific interactions are the result of activity and/or activity patterns. Methods and materials .—A litter of varying lemmings was collected at Umiat, Alaska, and transported to Fort Collins, Colorado. They survived to breed and establish a laboratory colony, on which this study is based. Four animals (2 males, 2 females) were housed in separate cages. Each cage was approximately 23.5 cm. wide by 28.5 cm. long …

One of the most frequently mentioned characteristics of the varying lemming ( Dicrostonyx ) is the growth of enlarged claws on the 3rd and 4th digits during the winter. Hinton (monograph of the voles and lemmings [microtinae] living and extinct. London, p. 139, 1926) pointed out that in summer the claws do not differ greatly from those of other lemmings; but in winter “they are very large, sometimes exceeding half an inch in length, and have the appearance of being double, each of the two fingers seeming to bear two enormous claws, one on top of the other, which are separated at their tips by a more or less deep notch.” It was formerly believed that the growth of bifid claws was a characteristic of only the “old lemmings in winter pelage.” However, Degerbol and Mohl-Hansen (Med. Om. Gronl. 131.) : 14, 1943) have pointed out that young born during the winter also develop bifid claws. In a captive colony of varying lemmings, D. groenlandicus rubricates (Richardson), stemming from Umiat, Alaska, I find that adults, as …

Reports on the occurrence of extra teeth in rodents are comparatively rare, and so far as I am aware have dealt with extra cheek teeth. While examining the skulls of varying lemmings ( Dicrostonyx groenlandicus rubricatus (Richardson)) that had died in captivity, I found one skull in which there were two incisors in the left dentary bone. Upon examination of the other dentary, it was found that it too had once possessed …