Pinyon-juniper (Pinus monophylla–Juniperus osteosperma) woodlands are expanding into shrubsteppe ecosystems in western portions of the Great Basin. Often, highly competitive trees displace the understory, and prescribed fire is increasingly used as a restoration tool. To inform management decisions about post-fire recovery, we examined immediate and long-term (i.e., 2 growing seasons) responses of the germinable seed bank to a spring prescribed fire. One week before and 1 week after a May 2002 prescribed burn, soil samples were taken under P. monophylla trees, under Artemisia tridentata ssp. vaseyana shrubs, and from interspace microsites. Two growing seasons after the prescribed burn, soil samples were taken from the same microsites and from similar microsites in an adjacent unburned area. Prior to the burn, the germinable seed bank under shrubs contained the highest seed density and the highest species richness followed by interspace and tree microsites. Shrub litter was consumed by the burn, causing complete loss of the seed bank from that microsite and depleting the A. tridentata seed bank. Interestingly, the density of germinable seeds in soil under P. monophylla trees increased immediately following the burn; 70% of that increase originated from the annual forb Descurainia pinnata. Two growing seasons following the prescribed burn, no overall differences in germinable seed density between burned and unburned plots were observed, but seed bank species composition differed, with seed banks in the prescribed burn having a greater abundance of Eriogonum elatum, E. microthecum, and Gayophytum diffusum compared to unburned plots, which had a greater abundance of A. tridentata, Lappula occidentalis, and Descurainia pinnata. Our results indicate that rapid restoration to prefire vegetation cannot rely upon the soil seed bank. To ensure rapid recovery, land managers should select sites for prescribed burns that have fire-tolerant perennial vegetation.

Nomenclature: USDA, NRCS. 2006. The PLANTS Database [cited 13 November 2006]. National Plant Data Center, Baton Rouge, LA 70874–4490. Available from:  http://plants.usda.gov

We tested for changes in forest structural classes from 1860 to 1940 in 26 dry Pinus ponderosa–Pseudotsuga menziesii stands of northeastern Washington. In 1860 historical fire regimes and associated forest structure remained mostly intact; aerial photos of national forest lands in eastern Washington were taken 70–80 years later and used as historic reference points in regional resource assessments. We determined changes in stand age, tree density, and number of age cohorts per stand between 1860 and 1940. Also, we evaluated whether stand age-class structure in 1860 was in agreement with fire-scar analysis estimates of the historical fire regime. We developed a forest structure classification based on age cohorts and found that forest structural classes varied significantly (P < 0.001) from 1860 to 1940. From 1860 to 1940, average stand age increased by 26% and number of age cohorts per stand increased by 18%. Stands in stand initiation structural classes declined from 27% to 4%; stands in old forest structural classes increased from 23% to 49%. We suggest the 1940 photo record, previously used to assess historical conditions, may provide a false metric of structural complexity for historical dry fir-pine forests in eastern Washington. Competing interpretations of stand age-class structure in 1860 prevented the conclusive verification of historical fire regimes.

Livestock grazing is one of the most common forms of land use in the western United States, yet scientists struggle to accurately predict grazing impacts. This study examined the initial response of desert horned lizards (Phrynosoma platyrhinos) to cattle introduction at a site in northwestern Utah. We sampled 21 grazed and 7 ungrazed study plots before grazing (2001), after grazing (2002), and 1 year after the cessation of grazing (2003). We were specifically interested in whether grazing influenced lizards through biotic or abiotic pathways. Lizard response (based on scat counts) to the initial impact of grazing (<6 months after cattle introduction) suggests that lizards abandoned areas protected from grazing (i.e., ungrazed exclosures) presumably in favor of grazed areas. Avoidance of ungrazed plots by lizards coincided with a decline in shrub and grass cover on grazed plots and with no significant change in relative abundance or richness of prey (ants) on grazed plots. In 2003, one year after cattle had been removed from the site, prey species richness declined on ungrazed plots, and percent bare ground increased on previously grazed plots; however, we detected no response of lizards to these changes. Overall, these results add to a growing consensus that responses by small vertebrates to grazing are largely the result of changes to habitat structure (i.e., vegetation cover), rather than to changes in prey availability. Importantly, results from our relatively unique evaluation of initial grazing impacts corroborate results from more classic grazing studies conducted sometime after grazing has commenced and suggest that responses of small vertebrates to changes in habitat structure may be generalizable.

We compared pellet, burrow, visual, and camera surveys to identify a method with high efficiency for detecting current pygmy rabbit (Brachylagus idahoensis) presence at a site in summer. We used 20 known occupied sites in 4 regions of northern Nevada and eastern California for the comparison. All leporid species that occurred in the region were distinguishable in photographs, and camera surveys had a 95% detection efficiency for pygmy rabbits. Burrows were detected at 85% of total sites; however, burrows that appeared active were found at only 55% of total sites. Pygmy rabbit pellets were found at all sites, but fresh pellets were observed at only 70% of the sites. Sighting surveys detected pygmy rabbits 30% of the time. Only camera and visual surveys provided conclusive evidence of current presence. Of these methods, camera surveys were more efficient because they allowed for a longer period of detection. We also evaluated the use of road transects to detect and determine relative abundances of rabbit species in an area. Road transects detected pygmy rabbit presence in 6 of 10 transects. Relative abundance among species was biased against pygmy rabbits because of the dense vegetation they prefer to live in, their limited home ranges, and other behavioral characteristics.

We compared the life cycles of Claassenia sabulosa (Banks 1900) and Hesperoperla pacifica (Banks 1900) (Plecoptera: Perlidae) in allopatry and sympatry by studying 4 populations in 3 streams of the South Platte River Watershed, Colorado. We estimated 2-year life cycles for both C. sabulosa and H. pacifica in allopatry and sympatry. Evidence of egg diapausing and extended larval recruitment was noted for both species in allopatry and sympatry. There were no apparent differences in larval growth, larval recruitment, or adult emergence periodicity between allopatric and sympatric populations of C. sabulosa. In contrast, allopatric and sympatric H. pacifica populations exhibited differences in the timing of larval growth, larval recruitment, and adult emergence. We feel that the differences in the life cycles of these populations were likely related to water temperature because a substantial water temperature difference (degree days of 1761 and 2563) occurred between study reaches. In sympatry, H. pacifica adults began emerging 2 weeks earlier than C. sabulosa, when water temperature reached 9°C. The emergence of H. pacifica was synchronous and male biased. The emergence of C. sabulosa was protandrous and male biased and began when water temperature reached 17°C. Claassenia sabulosa emergence was extended and lasted for 6 weeks during July and August. The abundance of C. sabulosa adults during this period corresponded closely to fluctuations in water temperature.

Many rodent species scatter hoard seeds within a home range shared with other seed-caching animals. An animal foraging for cached food is likely to encounter the caches of other animals, as well as its own. This study asks the following question: do animals recover primarily their own caches, do they conserve their own caches and search for the caches of other animals, or do they search indiscriminately for cached seeds regardless of who buried them? We tested these ideas using 8 yellow-pine chipmunks inside rodent-proof enclosures. We allowed each subject to cache radioactive seeds, we located the seed caches, and then we paired each rodent cache with an artificial cache in a similar microsite. During search trials, 7 subjects removed mostly their own caches, and 1 subject removed similar numbers of its own caches and paired artificial caches. These results suggest that most yellow-pine chipmunks actively search for food that they have stored, apparently using spatial memory rather than relying on olfaction. However, previous studies have established that chipmunks also are very effective pilferers of caches made by other animals. This apparent discrepancy may result from a difference between enclosures and field sites in the proportion of “own” caches to total caches.

The New Zealand mud snail (NZMS), Potamopyrgus antipodarum (Gray), is an invasive species of aquatic snail that is becoming widespread in inland and coastal waters of the western United States. The New Zealand mud snail can have significant impacts on stream ecosystems, as they may consume a large fraction of available algae production and compete with and displace native invertebrates. Even though the distribution of this species is expanding, the habitat conditions conducive to invasion are incompletely understood. Surveys following the NZMS invasion in the Upper Owens River, California, indicated that the snail may be excluded from waters where dissolved solute content is low, so experimental studies were undertaken to evaluate survival and growth as a function of varied specific conductivity (SC) and calcium availability. Juvenile snails were collected from the Upper Owens River and reared in dilutions of natural river water adjusted to 10, 50, 100, 200 and 300 μS · cm⁻¹ SC. Experiments were also conducted with newborn clones raised in river water dilutions ranging from 25 to 200 μS · cm⁻¹ to examine mortality and growth at this sensitive stage of development. In addition, calcium-free artificial river water was prepared at 200 μS · cm⁻¹ to test for the independent effect of limitation of this mineral ion required for shell-building. Significant reductions in survival and growth occurred among treatments diluting river water from 300 to 50 μS · cm⁻¹. No growth was found at or below 25 μS · cm⁻¹. Growth was also inhibited in calcium-free artificial water compared to natural river water with the same SC, showing that lack of this mineral impedes development. These results suggest that many streams in the range of 25–200 μS · cm⁻¹ cannot support productive NZMS populations and that nuisance invasions may be most prevalent in waters above 200 μS · cm⁻¹ where sufficient dissolved mineral content is present for growth.

In the southwestern United States, Brassica tournefortii (Gouan) is a highly invasive plant that threatens native annuals. We conducted 5 experiments to help define the environmental limits for B. tournefortii germination. We found that this species germinates at a wide range of temperatures (16°C to 32°C), under moderate salt concentrations (up to 3.20 dS · m⁻¹), in 24 hours of light or darkness, and after 10 weeks of submergence in water. These germination characteristics make B. tournefortii a potentially vigorous competitor of native annuals in the Mojave Desert. The fact that B. tournefortii can take advantage of and effectively reproduce in habitat altered by Tamarix spp. adds to management concerns for controlling this species. That B. tournefortii seeds remain viable after extended submergence, combined with our observation that B. tournefortii can float across large bodies of water with seed pods intact, indicates that this species is a highly successful invader and may be a threat to natural environments, including remote shoreline habitats. We can no longer assume that shoreline habitats experiencing little to no human contact will be safe from invasions initiated by humans.

This is the 1st effort to determine the mating behavior of the Tehuantepec jackrabbit (Lepus flavigularis), an endangered endemic species from southern Mexico whose distribution is limited to the Isthmus of Tehuantepec region. Between June 2006 and December 2007, observations of 60 adult radio-marked jackrabbits were carried out in Santa María del Mar, Oaxaca, Mexico. Direct observations showed that the breeding season of the Tehuantepec jackrabbit lasted an average of 200 days per year, with a high-intensity period during the rainy season (May–October); we also confirmed a polygamous reproductive behavior for this species. More importantly, we showed that the Tehuantepec jackrabbit has a polygynous mating behavior. In a single night, a male courted and mounted an average of 2 females; whereas during the whole reproductive season, the male courted an average of 6 females and mounted 3 of them. In a single night, a female was courted by an average of 3 males but mounted by only 1 of them. Throughout the whole reproductive season, the female was courted by 5 males but mounted only by 1 of them. This is the 1st research concerning mating behavior of the Tehuantepec jackrabbit; the resultant information will be very useful for the jackrabbit's conservation, management, and reproduction in captivity.

Little is known about the disturbance history of low-elevation forest and steppe vegetation in the western United States, nor about the relative importance of climate and human activity in shaping present-day plant communities. We analyzed pollen and high-resolution macroscopic charcoal records spanning the last 2100, 1000, and 550 cal years from 3 small lakes in Jackson Hole, Wyoming, to reconstruct the vegetation and fire history along a gradient from steppe to dry forest. The pollen data suggest little change in vegetation in the last 2 millennia, aside from a long-term trend toward more forest at the expense of steppe. One site showed an expansion of mesophytic taxa in the last 350 years as a result of local changes in hydrology, and another site was dry prior to ad 1000 and showed fluctuations in steppe composition thereafter. The longest record suggests that fire frequency was higher before ad 1200 than after. Comparison of 3 charcoal records for the last 550 years indicates widespread fire episodes in ad 1980–2000, 1780–1810, ca. 1550, and 1420–1430. Changes in the vegetation and fire history of the last 2000 years show a response to effectively drier conditions prior to ad 1200 and wetter conditions during the Little Ice Age. Evidence of human influences was muted at best. Native Americans apparently did not alter the vegetation and fire regimes significantly during their occupation of Jackson Hole. Euro-American activities also had minor registration in the paleoecologic record: humans may have been directly responsible for fires in the mid- and late 19th century and indirectly responsible for the recent expansion of forest at the end of the 20th century.

Through dam-building activity, beavers (Castor canadensis) play an important role in creating pond and wetland habitat for bird communities. Their impact may be intensified in semiarid landscapes and may increase with increasing dam density on a stream. Our objective was to examine relationships between dam density, riparian area characteristics, and the riparian bird community in a semiarid landscape. In 2002 and 2003 we surveyed riparian birds, riparian area characteristics, and the number of dams along 1.2-km sections of 11 streams in sagebrush steppe regions of Wyoming. We categorized the riparian bird community into 2 assemblages based on their affiliation with terrestrial or aquatic riparian habitats. Average width of the woody riparian zone, average riparian shrub height, and percent cover of emergent vegetation all had significant positive relationships with dam density, but percent cover of ponded water did not. Species richness and abundance of all riparian birds, and of the terrestrial assemblage, increased significantly with increasing woody riparian zone width. In contrast, richness and abundance of the aquatic assemblage were significantly positively influenced by cover of emergent vegetation and ponded water. When we accounted for riparian area characteristics, we found that total species richness, total abundance, and aquatic assemblage abundance were each positively correlated with dam density, suggesting that dam density is related to other riparian characteristics selected by birds. Our results suggest increasing dam-building activity may be important in creating favorable riparian conditions for a rich and abundant bird community in semiarid regions.

Soil disturbances across a wide range of spatial scales have been found to promote the establishment of invasive plant species. This study addresses whether mounds built by northern pocket gophers (Thomomys talpoides) in the shrubsteppe environment of north central Washington are facilitating plant invasions into native-dominated fields. Research was conducted in native-dominated plant communities adjacent to exarable, nonnative-dominated fields. To determine the effect of mounds on plant growth, we recorded new establishment and persistence of all plant species over 2 growing seasons on 10–19 mound and intermound areas in 10 fields. Nonnative plant establishment was not affected by mounds, but native plant establishment, particularly of the dominant native Pseudoroegneria spicata was lower on mounds than on intermounds. Early in the growing season, mounds had reduced soil moisture, bulk density, soil strength, N mineralization rates, and total N and C concentrations, and similar extractable NO₃⁻ concentrations relative to intermound soils. Our results did not suggest that soil disturbance improved nonnative growth resulting in competitive suppression of natives; rather, our results suggested that low soil moisture and slow N mineralization rates on mounds in this ecosystem present relatively stressful conditions for native plant growth.

The eastern pipistrelle (Perimyotis subflavus) is relatively common and widespread throughout the eastern United States. In recent decades, the distribution of P. subflavus has expanded westward across the Great Plains, and little information exists on its natural history in this region. In east central Nebraska, we monitored the use of a mine by eastern pipistrelles for >1 year. A few males occupied the roost in summer, but during the period of hibernation (late September–early May), the mine was used by at least 30 individuals composed of both sexes. Most individuals first entered the mine during late September through mid-October and exited by mid-May, with numbers of individuals fluctuating throughout winter. In winter, most individuals roosted along outer passageways of the mine, but in other seasons individuals were scattered throughout the mine. Females had significantly greater body masses than males upon entering the mine in autumn and before exiting the mine in spring. Both sexes had significantly heavier body masses in autumn than in spring. Overall, 55% of individuals marked in spring returned in autumn. Males had a higher return rate (69%) than females (46%) over a single summer. Many aspects of the natural history of P. subflavus in Nebraska are similar to those reported from eastern but not from southern parts of its distribution.

Observations of shoaling and feeding behavior of the zooplanktivorous June sucker, Chasmistes liorus, were made during summer 2003 in Red Butte Reservoir, Utah. Water clarity limited observations to 0.5–1.5 m below the water surface. Schools of adult suckers, ranging from a few to >200 fish, were observed on 20 days from May to September. I classified them as schools rather than shoals because the groups moved synchronously rather than appearing simply as an aggregation of fish. These schools were near the water surface, generally in areas of the reservoir with a water depth of >3 m, and presumably fed on the zooplankton in the epilimnion. Juvenile suckers (age-1 and age-2) were observed only on a few occasions, near inundated vegetation. Age-0 suckers were observed in large shoals (aggregations of hundreds of fish) near the surface in the shadows of inundated vegetation in July and August. Juvenile suckers (age-0, age-1, and age-2) were always observed in age-specific shoals, while suckers in adult schools had a wider range of sizes.

During research on black-tailed prairie dogs (Cynomys ludovicianus), we repeatedly observed a female American badger (Taxidea taxus) hunting prairie dogs on a colony in southern Phillips County, Montana. During 1–14 June 2006, we observed 7 aboveground attacks (2 successful) and 3 successful excavations of prairie dogs. The locations and circumstances of aboveground attacks suggested that the badger improved her probability of capturing prairie dogs by planning the aboveground attacks based on perceptions of speeds, angles, distances, and predicted escape responses of prey. Our observations add to previous reports on the complex and varied predatory methods and cognitive capacities of badgers. These observations also underscore the individuality of predators and support the concept that predators are active participants in predator-prey interactions.