Denning chronology of black bears in eastern Rocky Mountain National Park, Colorado

Understanding factors influencing the timing of den entrance and emergence of black bears ( Ursus americanus ) provides insight for bear management. We determined den entrance and emergence dates for bears in Rocky Mountain National Park (RMNP) and related these dates to vegetative productivity, weather, habitat, and demographic factors to assess the influence of these factors on denning chronology. Date of den entrance was most strongly influenced by age class, precipitation, and proportion of human-use areas in annual home ranges. Den entrance was typically later for adult bears during wetter years and when annual home ranges contained a greater proportion of human-use areas. Sex and presence of human-use areas were most strongly related to den emergence. Male bears typically emerged from dens before females, and bears emerged from dens earlier when human-use areas composed a greater proportion of annual home ranges. Collectively, our results suggest that denning behavior of black bears in RMNP was strongly influenced by presence of human-use areas, likely because of foods associated with such areas. Managers of black bears in RMNP can use precipitation to predict relative dates of den entrance, thereby allowing for more efficient strategies to combat potentially negative human–black bear encounters.     

Soil properties associated with vegetation patches in a Pinus ponderosa —bunchgrass mosaic

Since Euro-American settlement, fire exclusion and other factors have dramatically altered interior western coniferous forests. Once open and parklike, present-day structure in many southwestern Pinus ponderosa forests consists of dense stands of young, small-diameter trees, with small patches of larger, old trees, and relict open bunchgrass areas. Our objectives were to assess differences in soil properties associated with these different vegetation patches. We examined soil morphological characteristics, pH, organic C concentration, total N concentration, C:N ratio, and phytolith concentration from profiles within 6 transects (18 soil pedons) crossing patches of dense stands of small diameter trees, patches of old-growth trees, and open grassy areas. Results indicate that old-growth plots had significantly lower A horizon pH and thicker O horizons than grass plots. In general, we found vegetation patches had statistically similar C and N concentrations and C:N ratios for A and B horizons; however, C in the A horizon was positively correlated with O horizon accumulation ( r 2 = 0.79). Greater accumulation of organic C in the A horizon of forested areas contrasts with commonly reported results from mesic, mid-continental prairie-forest ecosystems but is typical for many arid, semiarid, and humid savanna ecosystems. Phytolith concentration was similar among old-growth pine, dense younger pine, and open grassy plots; the lack of a spatial pattern in phytolith distribution could indicate that grass cover was more spatially continuous in the past. Additionally, this interpretation is consistent with current theories regarding historical vegetation change in these forests.     

Habitat features and predictive habitat modeling for the Colorado chipmunk in southern New Mexico

Two subspecies of Colorado chipmunk (state threatened and federal species of concern) occur in southern New MeXico: Tamias quadrivittatus australis in the Organ Mountains and T. q. oscuraensis in the Oscura Mountains. We developed a GIS model of potentially suitable habitat based on vegetation and elevation features, evaluated site classifications of the GIS model, and determined vegetation and terrain features associated with chipmunk occurrence. We compared GIS model classifications with actual vegetation and elevation features measured at 37 sites. At 60 sites we measured 18 habitat variables regarding slope, aspect, tree species, shrub species, and ground cover. We used logistic regression to analyze habitat variables associated with chipmunk presence/absence. All (100%) 37 sample sites (28 predicted suitable, 9 predicted unsuitable) were classified correctly by the GIS model regarding elevation and vegetation. For 28 sites predicted suitable by the GIS model, 18 sites (64%) appeared visually suitable based on habitat variables selected from logistic regression analyses, of which 10 sites (36%) were specifically predicted as suitable habitat via logistic regression. We detected chipmunks at 70% of sites deemed suitable via the logistic regression models. Shrub cover, tree density, plant proximity, presence of logs, and presence of rock outcrop were retained in the logistic model for the Oscura Mountains; litter, shrub cover, and grass cover were retained in the logistic model for the Organ Mountains. Evaluation of predictive models illustrates the need for multi-stage analyses to best judge performance. Microhabitat analyses indicate prospective needs for different management strategies between the subspecies. Sensitivities of each population of the Colorado chipmunk to natural and prescribed fire suggest that partial burnings of areas inhabited by Colorado chipmunks in southern New Mexico may be beneficial. These partial burnings may later help avoid a fire that could substantially reduce habitat of chipmunks over a mountain range.     

Comparison of two roadside survey procedures for dwarf mistletoes on the Sawtooth National Forest, Idaho

Two roadside surveys were conducted for dwarf mistletoes parasitizing lodgepole pine and Douglas-fir on the Sawtooth National Forest, Idaho. One survey used variable-radius plots located less than 150 m from roads. The 2nd survey used variable-radius plots established at 200-m intervals along 1600-m transects run perpendicular to the same roads. Estimates of the incidence (percentage of trees infected and percentage of plots infested) and severity (average dwarf mistletoe rating) for both lodgepole pine and Douglas-fir dwarf mistletoes were not significantly different for the 2 survey methods. These findings are further evidence that roadside-plot surveys and transect-plot surveys conducted away from roads provide similar estimates of the incidence of dwarf mistletoes for large forested areas.     

Exercise conditioning decreases downstream movement of pond-reared razorback suckers released into a stream environment

Despite augmentation stocking efforts, wild populations of razorback suckers ( Xyrauchen texanus ) continue to decline. Endangered razorback suckers are commonly raised in off-channel ponds until maturity (approximately 300 mm TL) and then stocked into the Colorado River or its tributaries. After fish are stocked, they commonly move large distances downstream. We conducted an experiment to determine if downstream dispersal could be reduced through exercise conditioning. Two groups of razorback suckers, exercised and nonexercised, were released into Fossil Creek, Arizona. Prior to release, a subsample from each treatment group was tested in a laboratory flow chamber. Razorback suckers that had been exercise conditioned were able to maintain a position in the flow chamber 2 times longer and at velocities 25 cm · s –1 higher than nonexercised fish. Although the intended method of field data collection via passive-integrated-transponder (PIT) antennas and a remote communication station failed because river otters ( Lontra canadensis ) preyed upon the released razorback suckers, implanted PIT tags were retained in otter scat. Recovered PIT tags enabled distributional analysis, which indicated that exercised razorback suckers did not move as far downstream from the point of release as nonexercised razorbacks. Exercise conditioning may increase overall fitness of pond-reared razorback suckers, and, consequently, increase the effectiveness of augmentation stocking. A pesar de los esfuerzos de repoblación, las poblaciones silvestres del matalote jorobado ( Xyrauchen texanus ) siguen en declive. Los matalotes jorobados, que están en peligro de extinción, se crían en estanques fuera del cauce hasta la etapa adulta (~300 mm) y después son liberados en el Río Colorado o uno de sus afluentes. Los peces suelen desplazarse largas distancias río abajo después de su introducción al río. Llevamos a cabo un experimento para determinar si la dispersión río abajo se podía reducir mediante el acondicionamiento por ejercicio. Dos grupos de matalotes fueron liberados en Fossil Creek, Arizona, uno que había sido acondicionado y otro que no. Antes de liberarlos, examinamos una submuestra de cada grupo en una cámara de flujo en el laboratorio. Los matalotes que habían sido acondicionados por ejercicio pudieron mantener sus posición en la cámara de flujo dos veces más tiempo y a velocidades de 25 cm · s –1 más altas que los peces no acondicionados. Aunque falló el método de colecta de datos mediante antenas de sistema PIT (passive integrated transponder) y una estación remota de comunicación, los matalotes liberados fueron depredados por nutrias de río ( Lontra canadensis ) y las marcas PIT implantadas se quedaron en las heces de las nutrias. La recuperación de estas etiquetas PIT permitió un análisis de distribución que indicó que los matalotes acondicionados no se desplazaron río abajo tan lejos del punto de liberación como los matalotes no acondicionados. El acondicionamiento por ejercicio podría mejorar la condición física de los matalotes jorobados criados en cautiverio y así aumentar la eficacia de la reintroducción.     

Canyon grassland vegetation changes following fire in northern Idaho

Native and nonnative vegetation mosaics are common in western rangelands. If land managers could better predict changes in the abundance of native and nonnative species following disturbances, maintenance of native plant cover and diversity may be improved. In August 2000, during suppression of a wildfire near Lewiston, Idaho, a backing fire burned canyon grassland plots. A previous study had recorded species composition and cover prior to the fire, so we were able to evaluate changes in species composition and abundance on established plots before and after the fire. Overall, summer burning had little effect on the grassland communities. Pseudoroegneria spicata recovered to prefire coverage by the third postfire year. In the third postfire year, cover of native and nonnative annual species was significantly greater on burned than unburned sites ( P Bromus tectorum cover increased, as expected, on burned plots. Prefire and postfire cover values for Centaurea solstitialis were nearly equal, and there were no significant cover differences between burned and unburned plots in any year. As part of this study, we also evaluated changes in the cover of dominant native and nonnative species with respect to their prefire seral stage on burned and unburned plots. Because our sample sizes were small, we only report community-level trends but suggest that this type of community analysis could make for an interesting future study. Los mosaicos de vegetación nativa y no nativa son comunes en los pastizales del occidente de Norteamérica. Si los administradores de tierras pudieran predecir mejor los cambios en la abundancia de especies nativas y no nativas después de las perturbaciones, se podría mejorar el mantenimiento de la cobertura y diversidad de las plantas nativas. En agosto de 2000, los remanentes de un incendio quemaron terrenos de pradera de cañón durante la supresión de un incendio cerca de Lewiston, Idaho. Un estudio previo registró la composición y cobertura de especies antes del incendio, por lo que pudimos evaluar los cambios en la composición y abundancia de especies en determinados terrenos antes y después del incendio. En general, las quemas de verano no afectaron mucho a las comunidades de pradera. Para el tercer año después del incendio, Pseudoroegneria spicata se había repuesto al nivel de cobertura que tuvo antes del incendio y la cobertura de especies anuales nativas y no nativas fue significativamente mayor ( P Bromus tectorum aumentó en los terrenos quemados. Los niveles de cobertura de Centaurea solstitialis antes y después del incendio fueron casi iguales, y no hubo ninguna diferencia significativa en la cobertura de los terrenos quemados y la de los no quemados en ninguno de estos años. Como parte de este estudio, también evaluamos los cambios en la cobertura de especies dominantes nativas y no nativas con respecto a su estado sucesional previo al incendio en terrenos quemados y no quemados. Debido a que tuvimos un reducido tamaño de muestra, sólo reportamos tendencias a nivel de comunidad, pero sugerimos que esta clase de análisis de comunidades podrían servir como modelo para estudios interesantes en el futuro.     

Rabbit abundance relative to rainfall and plant production in northern Chihuahuan Desert grassland and shrubland habitats

Rabbit abundance patterns in the North American Southwest are poorly known, particularly relative to the potentially important influences of rainfall and plant production. We conducted a 10-year study on the comparative densities of black-tailed jackrabbits ( Lepus californicus ) and desert cottontail rabbits ( Sylvilagus audubonii ) in relation to annual rainfall and plant production in both black grama ( Bouteloua eriopoda ) grassland and creosotebush ( Larrea tridentata ) shrubland habitats in the northern Chihuahuan Desert. We found that both species of rabbits were more abundant in black grama grassland than in creosotebush shrubland and that plant production was positively correlated with rainfall at both habitats. However, rabbit densities were not positively correlated with rainfall or plant production in either habitat. In fact, both species of rabbits exhibited gradual, multiyear changes in abundance rather than the patterns of high annual variation observed in desert rodent communities. Our findings of no significant relationship between plant production and rabbit densities indicate that rabbit abundance in the northern Chihuahuan Desert may not be strongly regulated by short-term, bottom-up effects of annual variation in plant production. Long-term trends indicate that other factors such as disease or predation may be equally or more important. We suggest that future research evaluate both top-down and bottom-up influences to elucidate the temporal dynamics of Chihuahuan Desert rabbit abundance. Se conoce poco sobre los patrones de abundancia de conejos desérticos en el suroeste de Norte America, particularmente en relación con las influencias potencialmente importantes de la precipitación y la producción de plantas. Llevamos a cabo una investigación de diez años sobre la densidad relativa de la liebre de California ( Lepus californicus ) y el conejo cola de algodón ( Sylvilagus audubonii ) en los hábitats tanto de pradera de grama negra ( Bouteloua eriopoda ) como de matorral de gobernadora ( Larrea tridentata ) en el norte del Desierto Chihuahuense, en relación con la precipitación y la producción anuales. Encontramos que ambas especies de conejo fueron más abundantes en la pradera de grama negra que en el matorral de gobernadora, y que la producción de plantas estuvo correlacionada positivamente con la precipitación en ambos hábitats. Sin embargo, las densidades de conejos no estuvieron correlacionadas positivamente con la precipitación o con la producción de plantas en ninguno de los dos hábitats. De hecho, en cuanto a la fluctuación de su abundancia, las dos especies de conejo exhibieron tendencias graduales a lo largo de varios años, en comparación con los patrones de gran variación anual que se han observado en comunidades de roedores desérticos. La falta de una relación significativa entre la producción de plantas y la abundancia de conejos, indica que la abundancia de conejos en el norte del Desierto Chihuahuense no está fuertemente regulada por los efectos ascendentes a corto plazo de la variación anual en la producción de plantas. Los cambios reflejados en las tendencias a largo plazo indican que otros factores como las enfermedades o la depredación pueden ser de igual o mayor importancia, y sugerimos que investigaciones futuras deberán evaluar tanto las influencias ascendentes como las descendentes para entender las dinámicas temporales en la abundancia de conejos del Desierto Chihuahuense.     

The anatomy and taxonomy of Vanclevea (Asteraceae)

Wood, leaf, and floral anatomy of Vanclevea stylosa is compared with that of several possibly related species in the genera Acamptopappus, Eastwoodia, Grindelia, Haplopappus, and Petradoria. Although V. stylosa was originally described as a Grindelia, it is clearly distinct from that genus. Of the taxa studied, it is most closely allied to Haplopappus salincinus and H. scopulorum. The taxonomy, morphology, and distribution of the monotypic Vanclevea are detailed, and known exsiccatae are listed.     

Nest of Formica propinqua (Hymenoptera: Formicidae)

The nest of the ant Formica propinqua W. M. Wheeler is reported from Washoe Co., Nevada.     

Habitat use of leatherside chub ( Gila copei ) in the presence of predatory brown trout ( Salmo trutta )

The objectives of this study were to (1) examine distribution and habitat use of leatherside chub ( Gila copei ) in a creek with high densities of predatory brown trout ( Salmo trutta ), and (2) compare study results with published accounts of leatherside chub habitat use in streams with few or no brown trout. A 14-km section of Diamond Fork Creek, Utah, was point-shocked to determine macrohabitat (main channel and lateral habitat) and microhabitat (current, depth, substrate, and cover) use of leatherside chug. At the macrohabitat level, leatherside chub were most common in lower reaches of Diamond Fork Creek where the channel was braided and lateral habitats (cutoff pools and backwaters) were abundant. Only a single leatherside chub was found in the main channel of Diamond Fork. Investigations in other systems lacking brown trout indicated that leatherside chub occupy main channel habitats. At the microhabitat level, we found significant positive associations between presence of leatherside chub and both habitat depth and silt. In addition, we found a significant negative association between presence of leatherside chub and number of brown trout. Our results suggest predation by brown trout may limit leatherside chub to lateral habitats that could provide refugia against predation. The introduction of brown trout to systems with little lateral habitat could have serious effects on persistence of resident leatherside chub populations.