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Results for “Southwestern Naturalist”

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At least 91 records · Page 5Linked to original sources
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↗
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↗