North-central Colorado Research Articles

Elevated and Floating Nest Structures for Canada Geese

Two types of goose nesting structures have been designed by the Colorado Division of Game, Fish and Parks. These structures are being used successfully by a resident flock of Canada geese (Branta canadensis) in north-central Colorado, primarily Larimer County. The two types of structures are: (1) an elevated single-pole structure which consists of a nest box mounted on a 9-ft post, and (2) a floating canoe-like platform which supports a nest box. The materials, construction, and suggestions for erecting both types of structures are discussed. The Colorado Division of Game, Fish and Parks became active in Canada goose propagation in 1957. Between 1957 and 1962, a total of 34 adult Canada geese, and 381 goslings obtained primarily from the Denver metropolitan flock, were released in Larimer County, north-central Colorado, in an attempt to establish a resident breeding population (Will 1969:5). By 1962, the resident flock was considered well established and in need of no additional introductions (Grieb 1963). At the end of the production season of 1968, the Larimer County flock totaled approximately 1,555 (Will 1969:126). Both the Denver and Larimer County flocks contain primarily giant Canada geese (Branta canadensis maxima) (Hanson 1965). Although Larimer County includes a great number of water areas, natural nesting sites for Canada geese are extremely limited. The success and growth of the resident population in recent years has been attributed to the availability of a large number and variety of nesting structures. Of the 440 goose nests established in 1967 and 1968, 59 percent were on man-made sites which included a variety of elevated, ground, and floating structures. In 1967, 59 percent of the 186 available nesting structures were used by nesting geese. In 1968, 68 percent 1Present address: Idaho Cooperative Wildlife Research Unit, University of Idaho, Moscow. of the 201 available structures were used. Nesting success on all types of structures uring the 2-year period was 76 percent, while nests on natural sites were only 51 percent successful. Of the 22 nests destroyed by predators during the 2 years, 18 (82 percent) were located on the ground while only 4 (18 percent) were located on nesting structures. Nest desertion appeared to be no greater on man-made sites than on natural sites. Two improved types of nesting structures are being used extensively in Larimer County and are far superior in construction, maintenance, and acceptability by Canada geese, to other types that have been tried. The two types are: (1) an elevated single-pole structure which consists of a nest box mounted on a single pole, and (2) a floating canoe-like platform which supports a nest box. G. I. Crawford is credited with the design of both types of nesting structures. Details on materials, dimensions, and suggestions for construction are available upon request. SINGLE-POLE NEST STRUCTURE The single-pole structure consists of a 6-inch x 9-ft post treated with pentachlorophenol, which supports a 19-X 32-inch nest box (Fig. la). One continuous piece of snow fence, with 21/4 inches between laths, is nailed to a top and bottom frame to

Effect of Snow Depth on Mule Deer in Middle Park, Colorado

Effect of Snow Depth on Mule Deer in Middle Park, Colorado

Some Comparisons of the Feeding Ecology of Four Owls in North-Central Colorado

Four species of owls (Great Homed Owl, Bubo virginianus; Long- eared Owl, Asio otus; Burrowing Owl, Speotyto cunicularia and Barn Owl, Tyto alba) which inhabit the same grassland habitats in northcentral Colorado were investigated to determine differences and similarities in feeding ecology. Consider- able overlap in prey species was found in the four owls. However, the average estimated prey weight was significantly different for each owl species. Differences in activity periods, foraging methods and predator-prey size relationships may all function in reducing interspecific competition among these owls. During 1967 observations were made on the feeding ecology of the Great Horned Owl (Bubo virginianus), Long-eared Owl (Asio otus), Burrowing Owl (Speotyto cunicularia) and Barn Owl (Tyto alba) on short-grass prairie or interspersed prairie and farmland in the eastern one-fifth of Larimer County, Colorado. Rock outcroppings, canyons and eroded ditches, all abundant in this area, provide nesting sites for Great Horned and Barn Owls. Small groups of trees along water- courses, wind breaks and orchards are utilized for nesting and roosting by Long-eared and Great Horned Owls. Both occupied and abandoned prairie dog towns attract Burrowing Owls during the nesting season. Blue grama (Bouteloua gracilis) and buffalo grass (Buchloe dacty- loides) are dominant grasses. On rocky soils where rock outcroppings appear, mountain mahogany (Cerocarpus montanus) is abundant. Cottonwoods (Populus spp.) are the most abundant trees and occur mostly along watercourses. Only a small percentage of the land at most of the areas studied was under cultivation. Very little published literature exists on the food habits of these owls in north-central Colorado. Reed (1957) examined Barn Owl pellets from Larimer County and Hamilton (1941) made observations on the food habits of Burrowing Owls in Denver County. Nothing, apparently, has been published on the food habits of the Great Horned and Long- eared Owls for this locality.

Ecological Distribution of Hydracarina in North Central Colorado

Ninety-nine species of Hydracarina were collected in an extensive survey of streams, lakes, ponds, and hot springs of north central Colorado during 1965, 1966, and 1967; 72 are new for Colorado and three are new for continental North America. The faunas of lentic and lotic habitats are distinct, with only four species contributing appreciably to both faunas. The stream fauna is composed of 44 species. When the 29 most common stream species are analyzed on the basis of their altitudinal distributions and their habitat ranges for bound carbonates, ash content, organic content, and temperature, four groups are evident: euryzonaleuryokous species, with wide altitudinal and habitat ranges; euryzonalstenokous species, with wide altitudinal but narrow habitat ranges; altitudinally restricted-euryokous species; and altitudinally restrictedstenokous species. The ecological basis for these groups is the variable adaptability of the water mites coupled with the physical-chemical characters of Rocky Mountain streams. The effects of substrate, stream velocity, and pollution on the distribution of Hydracarina were found to be significant, but highly localized; aquatic plants exert a negligible influence. The maximum number of species was found between 2450 and 2700 m, where faunas from higher and lower elevations overlap and where numerous small streams provide a great diversity of habitats. Zoogeographic affinities of stream species are with faunas to the north and west, suggesting colonization of this region by northern species. The fauna of hot springs consists of only two species: Thermacarus nevadensis, a species common in hot springs; and Tyrrellia circularis, not previously reported from hot springs. Lakes and ponds yielded 66 species; their low frequencies and low abundance reflect their haphazard passive dispersal and their sensitivity to environmental factors. The common lentic species also form four distinct groups: plains species, tolerant of high concentrations of dissolved salts and high temperatures; relatively stenokous montane species; alpine species, largely high-altitude stream forms that have invaded lakes; and euryzonal species, which are highly euryokous. Aquatic plants play a significant but highly localized role in the distribution of lentic Hydracarina. The greatest number of species occurs in nonalkaline plains lakes where a great variety of habitats are available and montane and plains faunas slightly overlap. Most species of lentic Hydracarina have a wide Holarctic and Nearctic distribution; there is a considerable overlap of eastern and western faunas, and a close affinity with the northwestern fauna in some genera. A comparison of lotic and lentic faunas indicates that their major differences are the product of the divergent nature of the two types of habitat, while similarities reflect characters common to the Hydracarina as a group. INTRODUCTION Though the Hydracarina live in a wide variety of aquatic habitats throughout the world, we know few details of their ecological distribu1 Contribution No. 52, Limnology Laboratory, University of, Colorado. 2 Present Address: Biology Department, Southwest Texas State College, San Marcos, Texas 78666.

Efficient Sectioning of Incisors for Estimating Ages of Mule Deer

Efficient Sectioning of Incisors for Estimating Ages of Mule Deer

EVOLUTIONARY STATUS OF THE ROCKY MOUNTAIN POPULATION OF WOOD FROGS.

The Wood frog, Rana sylvatica Le Conte, has an extensive distribution which ranges from Alaska south and eastward through much of Canada and the northeastern United States; a population assigned to R. s. cantabrigensis by Maslin (1947) occurs in the mountains of northcentral Colorado and southeastern Wyoming. Martof and Humphries (1959) studied the geographical variation in morphology of this species and concluded that no subspecific taxon was warranted. These workers noted, however, that the Mountain type, represented in their study by 12 specimens from southeastern Wyoming, 16 from northcentral Colorado, and two questionable ones from Yellowstone County, Montana, was most obviously different from the others. They assumed that Rana sylvatica is also distributed in the intervening areas of the Bitterroots and Rockies and, on their various maps, the Mountain type extends from Montana to northern Colorado and is continuous with the populations in Canada. No locality data were given to support such a distribution, nor are any specimens known from the area between the Medicine Bow Mountains in southeastern Wyoming to the northern tip of Idaho (see Figure 1 for known localities in Colorado and Wyoming). On the basis of habitat distribution alone, the Rocky Mountain population is certainly relict and isolated by a considerable distance from its kind in the north. This southern disjunct population undoubtedly reflects a southward displacement in the Wisconsin and subsequent return northward of these cold-adapted frogs after the close of the Wisconsin. Given sufficient time, speciation as a result of geographical isolation seems inevitable, but scanty data are ava.ilable bearing on ages of species or rates of divergence of sister populations. In a previous study of the Dakota Toad (Porter, 1968), I found that a measureable amount of divergence has occurred between the relict population in Wyoming and its kind in the Dakotas and Manitoba, but breeding experiments indicated the genetic divergence has not been sufficient to affect fertility rates or viability of progeny from interpopulational crosses. Presumably, the southern relict populations of Dakota Toads and Wood Frogs have been separated from their parental populations for about the same length of time. Thus, the purpose of the present study was to use both morphological and nonmorphological approaches to compare the Colorado-Wyoming Wood frogs with those in southern Canada, to determine the stage of speciation of this relict population, and to compare the results with those from the toad study.

Effect of Post-Emergence Weed Control on Grass Establishment in North-Central Colorado

Winter-fallowing, planting grass into a clean seedbed, and controlling weeds during the seedling year, has been a particularly successful range-improvement practice in north-central Colorado. During the S-year period (19641966), season-long hand weeding and spraying with 2,4-D when weeds were 6 to 12 inches high produced good stands in a year of average precipitation. However, neither spray ing at later dates nor mowing the weeds at any date reduced competition from weeds sufficiently to produce a satisfactory grass stand. In a wet year, weed control in the seedling stand was not beneficial. In a year of extreme drouth, satisfactory stands were not obtained with any level of weed control. It was concluded that a technique of planting into a clean seedbed and spraying to control broadleaf weeds during the seedling year of the grasses offers the best chance for a successful seeding if wind erosion does not become a serious problem.

DIPLOID AND AUTOTETRAPLOID PHYSARIA VITULIFERA (CRUCIFERAE)

Physaria vitulifera, a species endemic to the mountains of northcentral Colorado, is composed of diploid (2n = 8) and tetraploid (2n = 16) races that occupy distinct geographical areas. Morphological, cytological, and other experimental evidence suggests that the tetraploid plants arose as an autotetraploid race directly from the diploid race.

Food Habits of the Northern Pocket Gopher on Shortgrass Prairie

The food habits of Thomomys talpoides were studied in shortgrass prairie in north central Colorado. The following six plants comprised 88% of the yearly diet: Opuntia polyacantha (49.9% ), Stipa comata (12.1%), Sphaeralcea coccinea (10.3%), Agropyron smithii (10.1%) Bouteloua gracilis (3%), Atriplex canescens (2.5%). The yearly diet consisted of approximately 67% forbs, 30% grasses, and 3% shrubs; approximately 70% of the material eaten was aboveground parts of plants (stems and leaves). Opuntia was by far the most impor- tant food. It was eaten in all seasons, but was utilized most heavily in midwinter, when it comprised 79% of the diet and probably served most importantly as a source of water. In laboratory experiments T. talpoides thrived, using Opuntia as the only source of water. Certain ecological relationships resulting from the dependence on Opuntia by pocket gophers are discussed.

Jurassic and Triassic of Wyoming and Southern Rockies: ABSTRACT

Correlations of continental Triassic and marine Jurassic rocks in Wyoming, northwestern Colorado, and northeastern Utah are based on 150 measured sections. In central Wyoming, these rocks are about 1,000 ft thick and consist, from bottom to top, of the following formations: Crow Mountain and Popo Agie (Triassic), Nugget (Triassic? and Jurassic?), and Gypsum Spring and Sundance (Jurassic). The lower part of the Nugget has been named. South and east of the Wind River basin, rocks equivalent to the Crow Mountain are called the Jelm Formation. In northwestern Colorado and northeastern Utah, Jurassic and Triassic rocks discussed here are about 1,500 ft thick and consist, from bottom to top, of the following formations: Chinle (Triassic), Glen Canyon (Triassic and Jurassic), an Carmel and Curtis (Jurassic). These formations thin southeast toward central Colorado. Near Boulder they are represented by End_Page 1904------------------------------ only a 35-ft-thick equivalent of the Sundance. Particularly useful in correlation are purple and ocher analcime-rich rocks of the Popo Agie; the various units of the Redwater Shale Member and underlying member of the Sundance; and unconformities at the top of the Popo Agie, and at the base, in the middle, and near the top of the Sundance. The unconformity at the base of the Sundance is of Middle Jurassic age and is characterized by chert pebbles which occur in an area extending from the northeastern corner of Wyoming to Zuni, New Mexico (700 mi), and from the San Rafael Swell, Utah, to Boulder, Colorado (300 mi). The Jelm extends from Wyoming about 50 mi into north-central Colorado. The Popo Agie and the lower and upper parts of the Nugget of central Wyoming correlate with the lower and upper parts of the Chinle, and with the Glen Canyon of the Uintas, respectively. The Gypsum Spring as defined at the type section is represented by the unconformity beneath the chert-pebble zone at Manila, Utah, on the north flank of the Uintas. The Sundance correlates with the Curtis and Entrada, and possibly with part of the Carmel of Manila, Utah. End_of_Article - Last_Page 1905------------

Some Comparisons of the Black-tailed and White-tailed Prairie Dogs in North-Central Colorado

Black-tailed and white-tailed prairie dogs in north- auditory communications. The species differed markedly in the type, number, and construction me.thods of the burrow entrances. The black- tailed prairie. dogs altered their above-ground environment behaviorally, but the white-tailed did not. Both were diurnal, with two periods of maximum surface activity durin, the summer. Black-tailed prairie dogs generally confined their daily activities to definite boundaries; the white- tailed did not. Pups of both species spent considerable time in play. Pups of the black-tailed species displayed much care-soliciting behavior directed at the adults; pups of the white-tailed species did not. Black- tailed prairie dogs remained active above ground throughout the year, but with less total activity during winter than summer. White-tailed prairie dogs completely terminated surface activity during winter; adult males were the first to appear above ground in early spring and the first to become inactive in early summer; adult females appeared a little later and remained active slightly longer; pups remained active above ground until fall. Food habits varied with the time of year and the availability of vegetation. The black-tailed species ate mostly forbs and grasses, the white-tailed mostly grasses and sedges. The black-tailed prairie dogs consumed many roots; the white-tailed never ate roots. The density of burrow entrances and animals was greater for the black- tailed than for the white-tailed prairie dogs. The black-tailed species bred during late February; births occurred in late March and April, and the pups appeared above ground in early May. The white-tailed species bred in late March; births occurred in early May, and the pups appeared above ground in early June. There was no evidence to indi- cate yearlings were less successful breeders than adults with either spe- cies. There appeared to be no mortality between the time of conception and the initial appearance of the pups above ground for the black-tailed species, but almost 40% of the embryos were lost in this interval with the white-tailed species. Immigration and emigration played little part in the dynamics of the black-tailed species, but were more important for the white-tailed species. Badgers were the principal predators for both species and drowning contributed to mortality at both study sites. The black-tailed prairie dogs were longer than the white-tailed species, mostly because their tails were longer. Females of both species were similar in weight, but male white-tailed prairie dogs were heavier than the black-tailed of either sex.

Factors Influencing the Accumulation of Fallout 137Cs in Colorado Mule Deer

Concentrations of 137Cs were measured by gamma-ray spectrometry in mule deer muscle tissues, air, precipitation, soils, and twelve forage species which were sampled over a 3-y period in north-central Colorado. Maximum levels of 137Cs in air, vegetation and deer occurred in 1963. Spring peaks were noted for both air concentrations and deposition of 137Cs. Maximal deposition of 137Cs occurred when both precipitation and air concentrations were high, and fallout levels in soil generally increased with elevation and precipitation averages. Vegetation collected above 8500 ft was generally higher in 137Cs than vegetation collected at lower elevations. Plant species varied significantly in radiocesium burdens. Leaves were generally higher than stems in 137Cs content. Deer collected above 8500 ft were significantly higher in muscle 137Cs concentrations than deer collected at lower elevations. Levels of 137Cs in deer were highly correlated with the mean levels in vegetation collected during common time periods. Neither age nor sex produced statistically significant variations in muscle 137Cs concentrations. Inhalation, the drinking of surface waters, and the ingestion of snow were minor sources of 137Cs intake by deer in comparison to the ingestion of forage.

Density Studies of Mule Deer Body Fat

This paper reports on density measurements at temperatures ranging from 10–35°C of internal, subcutaneous and bone-marrow fat sampled from north-central Colorado mule deer. Density measurements were made on the ether extracts using the method of pycnometry. Regression equations for fat density as a function of temperature were estimated as 1/ D = (1.4813 × 10−3) T + 1.0385 for internal fat, 1/ D = (1.4075 × 10−3) T + 1.0461 for subcutaneous fat and 1/ D = (1.4878 × 10−3) T + 1.0371 for bone-marrow fat. Application of the density measurements to the quantitative estimation of body fat for mule deer is discussed.

Endogone--Food for Mice

Analysis of the contents of the digestive tracts of 450 mice trapped from 1955 to 1961 in a number of localities in northwestern Wyoming and north-central Colorado revealed 38% of the animals eating a hypogeous phycomycete, Endogone . The frequency of utilization was essentially the same for all species studied: Peromyscus maniculatus, Microtus longicaudus, Clethrionomys gapperi, Phenacomys intermedius and Zapus princeps . Consumption of the fungus appeared to be influenced by the season, the character and condition of the habitat and the availability of other foods. A comparison of data from stomach and cecal analyses suggests that stomach analyses alone provide a too conservative estimate of the frequency of utilization, but no dependable volumetric estimates of the amount of Endogone consumed can be made solely from cecal analyses.

The Lichen Flora of the Dakota Sandstone in North-Central Colorado

The Lichen Flora of the Dakota Sandstone in North-Central Colorado

The Lichen Flora of the Dakota Sandstone in North-Central Colorado

The Lichen Flora of the Dakota Sandstone in North-Central Colorado

Regional lake typology in northern Colorado, U.S.A.

Northcentral Colorado contains more than 400 lakes featured by an exceptionally wide range of limnological conditions. Four altitudinal limnological zones are characterized: the plains zone, which ...

Waterfowl Production during Wet and Dry Years in North-Central Colorado

quently during wet periods, when precipitation is maximum, resulting in the filling and relative maintenance of levels in land depressions. During the period of 1947-1955, precipitation reached annual highs and lows of wide diversity in north-central Colorado, as it did over much of the high-plains region. As a result, water levels here were high through 1949 and reached near-record lows in 1954 and 1955.

Annual Cycle of Net Plankton in a Fluctuating North‐Central Colorado Reservoir

Annual Cycle of Net Plankton in a Fluctuating North‐Central Colorado Reservoir

January Breeding of Peromyscus in North Central Colorado

Warren (the mammals of colorado, 1942) reported the breeding season of Peromyscus maniculatus in Colorado as “spring and summer” with occasional records in April and late September. Beidleman (Jour. Mamm., 35: 118, 1954) recorded October, 1952, breeding in Colorado Peromyscus as evidenced by one pregnant and nine lactating females, and two males with descended testes. Fourteen Peromyscus maniculatus were trapped January 2, 1954, in the foothills of northern Larimer County, Colorado at an elevation of 5700 feet. Two of the six females were pregnant; one contained five embryos five mm. crown-rump length and the other had six embryos of one mm. each. The testes of two males were scrotal in position. Testes length of all eight males varied from six to 11.0 mm. Beidleman (ibid.) and Brown (Ecology, 26: 308–309, 1945) associated late breeding with above-average temperatures and subnormal precipitation. Manville (Jour. Mamm., 33: 389, 1952) felt no...