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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 559 records · Page 31Linked to original sources
USGS1994

Are cicadas (Diceroprocta apache) both a "keystone" and a "critical-link" species in lower Colorado River riparian communities?

Apache cicada (Homoptera: Cicadidae: Diceroprocta apache Davis) densities were estimated to be 10 individuals/m 2 within a closed-canopy stand of Fremont cottonwood ( Populus fremontii ) and Goodding willow ( Salix gooddingii ) in a revegetated site adjacent to the Colorado River near Parker, Arizona. Coupled with data drawn from the literature, I estimate that up to 1.3 cm (13 1/m 2 ) of water may be added to the upper soil layers annually through the feeding activities of cicada nymphs. This is equivalent to 12% of the annual precipitation received in the study area. Apache cicadas may have significant effects on ecosystem functioning via effects on water transport and thus act as a critical-link species in this southwest desert riverine ecosystem. Cicadas emerged later within the cottonwood-willow stand than in relatively open saltcedar-mesquite stands; this difference in temporal dynamics would affect their availability to several insectivorous bird species and may help explain the birds' recent declines. Resource managers in this region should be sensitive to the multiple and strong effects that Apache cicadas may have on ecosystem structure and functioning.

Southwestern Naturalist↗
USGS1994

Species diversity, selectivity, and habitat associations of small mammals from coastal California

Species diversity and habitat associations were documented for small mammals along 16 transects in a semiarid part of coastal California. Peromyscus were the most abundant, comprising 45.3% of all captures, followed by Dipodomys (21.2%), Neotoma (15.1%), and Perognathus (15.0%). Five additional genera made up the remaining captures (3.4%). Peromyscus truei and Perognathus californicus were both common and widespread, accounting for 42.1% of all captures. Both species were found on all but one transect. Neotoma lepida, the third most common species, was captured on rock transects 96% of the time. Dipodomys elephantinus was the fifth most common species, and was found exclusively in chamise chaparral. Species diversity (H') averaged 1.22 and ranged from 0.33 on a chamise chaparral transect to 1.74 on another chamise chaparral transect which crossed the edge of a burn. Nearly all transects demonstrated this same trend for diversity to vary widely both within and between habitats, indicating that local conditions were more of an influence on diversity than broad habitat types. Selectivity, averaged across the ten most common species, was only 0.06, indicating that habitat selectivity was quite low. The most geographically widespread species, Peromyscus maniculatus, was the least selective (0.03), whereas the two species with the smallest geographic ranges, D. venustus and D. elephantinus, showed the greatest habitat selectivity (0.11 and 0.20, respectively). These values are much lower than those reported from short-term studies and suggest that, like species diversity, brief studies may not accurately reflect community-level interactions.

Southwestern Naturalist↗
USGS1994

An assessment of riparian environmental quality by using butterflies and disturbance susceptibility scores

The butterfly community at a revegetated riparian site on the lower Colorado River near Parker, Arizona, was compared to that found in a reference riparian site. Data indicated that the herbaceous plant community, which was lacking at the revegetated site, was important to several butterfly taxa. An index using butterfly sensitivity to habitat change (species classified into risk groups) and number of taxa was developed to monitor revegetation projects and to determine restoration effectiveness.

Southwestern Naturalist↗
USGS1999

Discovery of a second population of white-collared seedeaters, Sporophila torqueola (Passeriformes: emberizidae) along the Rio Grande of Texas

The range of the white-collared seedeater (Sporophila torqueola), a tropical grassland species, extends from Central America northward along both coasts of Mexico (Eitniear, 1997), including Tamaulipas and Nuevo Leon (Howell and Webb, 1995). White-collared seedeaters historically occurred commonly in extreme southern Texas (Oberholser, 1974; Rappole and Blacklock, 1994). However, since about 1950, white-collared seedeaters have undergone a precipitous decline in south Texas. Studies during 1994-1996 identified only seven to nine breeding pairs in the only population known to occur in Texas, located ca. 55 km downriver of Laredo, Texas, in Zapata Co. (Eitniear, 1997). Outside of the historical range, very few records are documented. Oberholser (1974) reported that three white-collared seed- eater specimens were collected in 1948 in Webb Co., northwest of Laredo, and Arnold (1980) also collected a white-collared seedeater in Webb Co. Vagrants also have been sighted as far afield as Corpus Christi (Blacklock, 1964), ca. 200 km north of the Rio Grande (Fig. 1).

Southwestern Naturalist↗
USGS2001

Experimental repatriation of boreal toad (Bufo boreas) eggs, metamorphs, and adults in Rocky Mountain National Park

The boreal toad ( Bufo boreas ) is an endangered species in Colorado and is considered a candidate species for federal listing by the United States Fish and Wildlife Service. Boreal toads are absent from many areas of suitable habitat in the Southern Rocky Mountains of Colorado presumably due to a combination of causes. We moved boreal toads from existing populations and from captive rearing facilities to habitat which was historically, but is not currently, occupied by toads to experimentally examine methods of repatriation for this species. Repatriation is defined as the release of individuals into areas currently of historically occupied by that species (Dodd and Seigel, 1991). This effort was in response to one of the criteria for delisting the boreal toad in Colorado stated in the conservation plan and agreement for the management and recovery of the Southern Rocky Mountain population of the boreal toad (Loeffler, 1998:16); "...there must be at least 2 viable breeding populations of boreal toads in each of at least 9 of 11 mountain ranges of its historic distribution." Without moving eggs from established wild populations, or from captivity to historical localities, it is doubtful whether the recovery team will attain this ambitions goal.

Colorado↗
USGS2001

Implications of seed size for seedling survival in Carnegiea gigantea and Ferocactus wislizeni (Cactaceae)

Larger seeds have been shown to convey benefits for seedling survival but the mechanisms of this process are not well understood. In this study, seed size and seedling survival were compared for 2 sympatric cactus species, Carnegiea gigantea (Engelm.) Britt. & Rose and Ferocactus wislizeni (Engelm.) Britt. & Rose, in laboratory and field experiments in the northern Sonoran Desert. Both species have small seeds, but Ferocactus seeds are nearly twice as long and 3 times as heavy as those of Carnegiea . The difference in size is perpetuated after germination: new Ferocactus seedlings have 4 times the estimated volume of new Carnegiea seedlings. In an outdoor experiment, annual survivorship of both species was low but was 6 times higher for Ferocactus (6 seedlings, 8.1%) than Carnegiea (1 seedling, 1.4%). The pattern of seedling mortality in relation to temperature and rain suggests that, after the initial flush of seed and seedling predation, drought and heat took a greater toll on Carnegiea than Ferocactus seedlings, probably because the larger seedling volume of Ferocactus conferred greater drought tolerance. In addition, F. wislizeni could become established without benefit of nurse plants whereas C. gigantea could not; this might reflect differential tolerance to high soil temperatures.

Arizona↗
USGS2001

Influence of changes in sagebrush on Gunnison sage grouse in Southwestern Colorado

The decline in abundance of the newly recognized Gunnison sage grouse ( Centrocercus minimus ) in southwestern Colorado is thought to be linked to loss and fragmentation of its habitat, sagebrush ( Artemisia ) vegetation. We documented changes in sagebrush-dominated areas between the 1950s and 1990s by comparing low level aerial photographs taken in these time periods. We documented a loss of 20% or 155,673 ha of sagebrush-dominated areas in southwestern Colorado between 1958 and 1993. The amount of sagebrush-dominated area was much higher and loss rates were much lower in the Gunnison Basin. We also found that 37% of plots sampled underwent substantial fragmentation of sagebrush vegetation. If current trends of habitat loss and fragmentation continue, Gunnison sage grouse (and perhaps other sagebrush-steppe obligates) may become extinct. Protecting the remaining habitat from further loss and fragmentation is paramount to the survival of this species.

Colorado↗
USGS2000

Abiotic factors affecting summer distribution and movement of male paddlefish, Polyodon spathula, in a prairie reservoir

Six male paddlefish, Polyodon spathula , were implanted with ultrasonic temperature-sensing transmitters and tracked during June through August 1997 to quantify effects of physicochemical conditions on their distribution and movement in Keystone Reservoir, Oklahoma. Paddlefish moved about twice as much during night than day. Movement rate of paddlefish was related to reservoir water level, inflow, and discharge from the reservoir at night; however, none of these variables was significant during the day. Location in the reservoir (distance from the dam) was negatively related to water level and positively related to inflow during day and night periods. Location in the reservoir was negatively related to discharge during the day. Paddlefish avoided the highest available water temperatures, but did not always avoid low dissolved oxygen concentrations. Paddlefish avoided the Cimarron River arm of the reservoir in summer, possibly because of high salinity. Our study demonstrates that distribution of paddlefish during summer and movement in Keystone Reservoir was influenced by physicochemical and hydrologic conditions in the system. However, biotic factors (e.g., food availability) not measured in this study may have been influenced by abiotic conditions in the reservoir.

Oklahoma↗
USGS2000

The swift fox in rangeland and cropland in western Kansas: Relative abundance, mortality, and body size

We assessed suitability of cropland and shortgrass rangeland for swift foxes ( Vulpes velox ) in western Kansas. Relative abundance and survival were similar for foxes in rangeland and cropland. Mortality resulting from non-traumatic causes, coyotes, and motor vehicles differed significantly between habitats. Predation by coyotes, motor vehicles, and non-traumatic causes were responsible for 45%, 36%, and 18%, respectively, of 11 deaths in rangeland and 20%, 10%, and 70%, respectively, of 10 deaths in cropland. Swift foxes in rangeland were larger and in better condition than those in cropland. Males were larger than females based on mass, standardized mass (mass/body length), body length, hindfoot length, and ear length.

Kansas↗
USGS2002

Taxonomic assessment of the black bear (Ursus americanus) in the eastern United States

The subspecific status of the Louisiana black bear ( Ursus americanus luteolus ) and Florida black bear ( U. a. floridanus ) were assessed using morphologic features to determine their distinctness in relation to one another and to the black bear ( U. a. americanus ). Forty-four dimensions were recorded from skulls of 125 male and 127 female adult (4.5 years or older) bears. Results showed skulls of U. a. luteolus, U. a. floridanus , and U. a. americanus to be similar in morphology. However, features of U. a. luteolus , and U. a. floridanus tended, in general, to be larger and shaped differently than those of U. a. americanus . Differences between measurements of U. a. luteolus and U. a. floridanus were less apparent than those between either of these taxa and U. a. americanus . For U. a. luteolus and U. a. floridanus , means of most characters differed only slightly, and ranges of all measurements overlapped to some degree. Yet, small numbers of characters that reflected molar tooth measurements or features relating to dentition, height of frontal region, and skull length and width appeared to correctly classify these taxa in most cases. Results were interpreted to support the subspecific recognition of U. a. luteolus, U. a. floridanus , and U. a. americanus .

Southwestern Naturalist↗
USGS2000

Predation on Corynorhinus townsendii by Rattus rattus

Corynorhinus townsendii (Townsend's big- eared bat) is a rare and declining species. Ex- tensive surveys for the coastal subspecies, C. t. townsendii, in California indicate that only 50% of historic maternity colonies are occu- pied currently (Pierson and Rainey, 1996). Three of the largest maternity colonies occur in Marin Co. Two of these have been moni- tored with evening exit counts on a regular basis since their discovery (1987-Randall House; 1990-Jerrys) through 1996. From 1987 through 1993, the Randall House colony slowly increased from 123 to 215 bats as the colony was afforded greater protection from disturbance once the bats were discovered. Since 1990, both colonies have been com- posed of ca. 200 adult bats in the spring, and ca. 300 adults and young through the summer and early fall.

Southwestern Naturalist↗
USGS2000

Status of translocated sea otters at San Nicolas Island, California

In the 1970s about 1,650 southern sea otters (Enhydra lutris nereis) were restricted to the central California coast (Riedman and Estes, 1990), and a high volume of oil was being shipped through the region. Because of the vulnerability of sea otters to contamination from oil (Costa and Kooyman, 1982; Williams and Davis, 1995) that would likely spread wide- ly along the shore after a large spill (Van- Blaricom and Jameson, 1982), the subspecies was listed as threatened in 1977 under the United States Endangered Species Act.

Southwestern Naturalist↗