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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 541 records · Page 30Linked to original sources
USGS1995

Minnesota wolf dispersal to Wisconsin and Michigan

Records are presented of three wolves that dispersed ≥200 km from northern Minnesota to the Minnesota-Wisconsin border, to southern Wisconsin, and to Michigan. This report documents that wolves cross major highways and other developed areas and that the recently recolonized wolf population in Wisconsin and Michigan could have originated from wolf populations in Minnesota other than those living along the Minnesota-Wisconsin border.

Michigan, Minnesota, Wisconsin↗
USGS1992

Distribution of Yellowstone grizzly bears during the 1980s

Grizzly bear ( Ursus arctos horribilis ) females with young occupied a greater proportion of area east of Yellowstone National Park during 1980-1989 compared to 1973-1979. Occupancy by all bears and females with young was lower in all peripheral areas compared to the Park, but greater east and south compared to north and south of the Park. Observed changes reflect not only a static or slightly increasing population trend, but may also reflect biases in data collection. These biases are discussed and distributions of all observations and females with young are presented. Methodological problems implicit in analyzing changes in distribution of grizzly bears are also discussed.

Idaho, Montana, Wyoming↗
USGS1993

Wolf nipple measurements as indices of age and breeding status

We measured nipple sizes of 29 captive wolves ( Canis lupus ), of known breeding histories, throughout the year and tested distinctions among various known breeding statuses of 20 wild wolves examined in northeastern Minnesota from May through September. For ca. 8 mo of the year only breeders and nonbreeders can be classified. Distinctions between current and former breeders were not reliable.

American Midland Naturalist↗
USGS1994

A single deer stands-off three wolves

The first record of a deer ( Odocoileus virginianus ) standing off three wolves ( Canis lupus ) is documented by an aerial observation in northeastern Minnesota.

American Midland Naturalist↗
USGS1999

Discovery of a new Kittlitz's murrelet nest: Clues to habitat selection and nest-site fidelity

On 13 June 1993, a new Kittlitz's murrelet ( Brachyramphus brevirostris ) nest was discovered near Red Mountain on the Kenai Peninsula, Alaska. The nest was on a 22° slope at about 900 m elevation with a northeast aspect, and contained a 60.2 × 40.6 mm egg that weighed 49.0 g. Downy feathers and weathered fecal material found at the nest indicated re-use from a previous year, suggesting possible nest site fidelity. The nest was located in an area scoured by winds and free of snow during early spring, suggesting that this may be an important mesoscale factor influencing selection of nesting habitat. Proximity to suitable foraging habitat, particularly sheltered bays and glacial river outflows, may affect breeding habitat choice over larger spatial scales.

Alaska↗
USGS1997

Survey and assessment of amphibian populations in Rocky Mountain National Park

We conducted surveys in Rocky Mountain National Park, Colorado for amphibians in 1987-1994. Four species, Ambystoma tigrinum, Bufo boreas, Pseudacris maculata, and Rana sylvatica , were recorded. Pseudacris maculata was the most widely distributed and abundant species in the Park. Two populations of E maculata were estimated to contain 161 and 136 breeding males in 1988. There was no evidence of a decline of A. tigrinum or R. sylvatica , but these species were found at relatively few locations. We did not detect Rana pipiens , which had been known previously from 3 locations in the Park. We found 7 breeding populations of B. boreas , which has declined recently elsewhere in the southern Rocky Mountains, but all but 2 of these populations were small and may not reproduce annually. At least one of these small populations is thought to have been extirpated. Estimated numbers of males in the 2 large populations, which are 6.4 km apart in the same drainage, were stable or increasing slightly from 1992 to 1995, averaging 189 and 239 individuals. Current and known locations of amphibians did not differ in elevation, size, lake type, presence of shallow water or emergent vegetation on the north shore, or presence of trout. Water chemistry at amphibian breeding sites was variable, but pH decreased significantly with increasing elevation. Causes of declines of B. boreas and R. pipiens are not known. Populations of B. boreas in the North Fork of the Big Thompson River are critically important to the conservation of this species in the Rocky Mountains.

Colorado↗
USGS2000

A comparison in Colorado of three methods to monitor breeding amphibians

We surveyed amphibians at 4 montane and 2 plains lentic sites in northern Colorado using 3 techniques: standardized call surveys, automated recording devices (frog-loggers), and intensive surveys including capture-recapture techniques. Amphibians were observed at 5 sites. Species richness varied from 0 to 4 species at each site. Richness scores, the sums of species richness among sites, were similar among methods: 8 for call surveys, 10 for frog-loggers, and 11 for intensive surveys (9 if the non-vocal salamander Ambystoma tigrinum is excluded). The frog-logger at 1 site recorded Spea bombifrons which was not active during the times when call and intensive surveys were conducted. Relative abundance scores from call surveys failed to reflect a relatively large population of Bufo woodhousii at 1 site and only weakly differentiated among different-sized populations of Pseudacris maculata at 3 other sites. For extensive applications, call surveys have the lowest costs and fewest requirements for highly trained personnel. However, for a variety of reasons, call surveys cannot be used with equal effectiveness in all parts of North America.

Northwestern Naturalist↗
USGS1989

Leopard frog and wood frog reproduction in Colorado and Wyoming

Between 1978 and 1988, we recorded reproductive information from populations of ranid frogs in Colorado and Wyoming. Egg masses from five plains and montane populations of northern leopard frogs ( Rana pipiens ) contained 645-6272 eggs (x̄ = 3045, N = 68 egg masses). In two montane populations of wood frogs ( Rana sylvatica ) numbers of eggs per egg mass varied from 711-1248 (x̄ = 876, N = 15) and probably were equal to total clutch size. Mean hatching success was 90% in egg masses from one R. sylvatica population and ranged from 70% to 99% in R. pipiens egg masses. Rana pipiens egg masses from one location were assigned to three overlapping size distributions, which we believe reflects the underlying age structure of female frogs.

Colorado;Wyoming↗
USGS1969

Wind training in some prairie trees

Asymmetry in tree crowns has been established for some time. Lawrence (Ecol. Monogr. 9:217-257, 1939) studied wind training, one cause of asymmetry, in the Columbia River Gorge. He and Boyce (Ecol. Monogr. 24: 29-67, 1954) cite the intensity and direction of wind during the growing season as the causative agents. In their study of trunk asymmetry, Potter and Green (Cology 45: 10-23, 1964) mention crown deformity in the open stands of trees. Prairie trees are typically found in open stands, and to our knowledge no quantitative studies have been done on their crown asymmetry. The present study on the nature of this asymmetry, is an attempt to fill the void.

Southwestern Naturalist↗
USGS1976

Fat content in migratory central Arizona Brazilian free-tailed bats, Tadarida brasiliensis (Molossidae)

Fat content of migratory Tadarida brasiliensis was determined during the spring, summer and fall of 1972 in the Verde Valley of Arizona. Fat indices were highest in March arrivals, generally declined throughout the summer, and were lowest in September. In both 1972 and 1973 bats had arrived at the study area by mid-March. In 1971 bats were last noted at the area in mid-October while in 1972 they had disappeared by late September. On the basis on physiological calculations it is estimated that bats collected in March 1972 possessed sufficient fat reserves to carry them a mean distance of 716 km north of the study area while September bats had only enough reserves to fly 386 km southward, about 160 km short of the nearest known Sonora wintering locality. It is suggested that in spring the bats may have a more rigidly timed migration and so put on excess fat to counter an uncertain environment to the north. The fall migration may be triggered by more unpredictable events, such as the passage of cold fronts, and less fat reserves may be required for movements into more favorable southern locales.

Arizona↗
USGS1984

Spawning by Rhinichthys osculus (Cyprinidae), in the San Francisco River, New Mexico

The speckles dace Rhinichthys osculus [Girard] is the most widely distributed and ubiquitous fish in the western United States (Moyle, Inland Fishes of California, 1976). Although common, very little information is available concerning thje reproductive behavior of speckled dace or the environmental cues which trigger spawning activity. Several hundred speckled dace were observed spawning in the San Francisco River, 4.8 km upstream from Reserve, Catron County, New Mexico, on June 2-3, 1981. Spawning was in an area of disturbed substrate at a time when other reaches of the streambed were overgrown with diatoms, filamentous algae, and macrophytes. This note described the spawning site and reproductive behavior and proposes that physical disturbance is a major cue for reproductive activity in the species.

New Mexico↗
USGS1989

Growth and fat-body cycles in feral populations of the African clawed frog, Xenopus laevis (Pipidae), in California with comments on reproduction

Feral populations of the African clawed frog ( Xenopus laevis ) exist in several areas of southern California. By following the first cohort of progeny produced by African clawed frogs at a recently colonized site, data on the growth rates and age at first maturity were obtained in field conditions. Females reached maturity at an earlier age than males, grew faster than males, and attained body lengths up to 25% larger than males. Larger females were capable of producing larger numbers of eggs than small females and, therefore, had greater reproductive potential. The relatively stable ambient temperatures of southern California contributed to the possibility of reproduction of clawed frogs during all but the coolest periods of the year. Cycles detected in the mass of fatbodies suggested that nutrients were mobilized from fat prior to and during ovulation. The amount of fat in females varies widely, but fat in males tended to accumulate as the males grew during the study period.

California↗