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Studies of rabbits and hares often use fecal pellet counts to estimate population density, create indices of abundance, and monitor habitat use, because fecal pellet counts are more easily deployed and less labor intensive than visual surveys and live trapping. In some habitats, plot size and shape can affect the measured pellet density and the resulting estimates of habitat use by rabbits. We compared rabbit (Sylvilagus spp.) fecal pellet density estimates derived from 0.155-m2 rectangular, 0.155-m2 circular, 1-m2 square, and 1-m2 circular plots in southern California chaparral and coastal sage scrub communities to evaluate habitat use by rabbits. Pellet plots were not an effective sampling design in our chaparral site where rabbit pellet density was low. Our coastal sage scrub site had an abundance of fecal pellets, and pellet density estimates varied by plot design. The 0.155-m2 plots were more easily deployed and counted, however they produced higher estimates of fecal pellet density, exhibited greater variance, and were unable to detect habitat differences in fecal pellet density. The 1-m2 plots required more effort but produced lower pellet density estimates, exhibited less variation, and were both able to detect habitat differences in fecal pellet density. We recommend that researchers conducting rabbit fecal pellet counts in Californian Mediterranean scrub habitats use 1-m2 circular plots for their ease of deployment, counting, and clearing and for their greater detection and precision in estimates of pellet densities.
Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) is a widespread shrub across the western United States, and there is great interest among scientists and land managers in its ecology and conservation, particularly with regard to maintaining structural heterogeneity of sagebrush stands for wildlife habitat and livestock forage. Yet little is known about its short-term regeneration dynamics and the implications of those dynamics for changes in stand structure. We examined changes among sagebrush size classes across 3 years, as well as emergence of sagebrush from seed bank and seed rain samples at 2 sagebrush shrubland sites in northern Utah: a lower-density site (1.4 plants/m2, SE 0.11) with no recent history of manipulation and a higher-density site (1.9 plants/m2, SE 0.21) that had recently been treated with herbicide to reduce sagebrush cover. On both sites, numbers of sagebrush plants in the largest size class decreased over the 3-year time period, while dead and medium-sized sagebrush plants increased. At the higher-density herbicide-treated site, this size class shift appeared to be driven by growth of small plants into the medium size class, likely associated with reductions in numbers of (and competition from) large plants. At the lowerdensity site, it appears that densities of large plants declined because the plants shrank in size, possibly due to herbivory. Sagebrush seed rain did not differ between fall and spring assessments. Forbs had the greatest representation in the seed bank, followed by grasses and then sagebrush, though the number of sagebrush seeds may be sufficient for seedling recruitment. These results illustrate that shifts among sagebrush size classes, especially transitions of small shrubs into the medium size class, may be a primary and immediate pathway of stand recovery, in addition to recruitment from seed. These findings underscore the importance of sagebrush stand structure to plant community health and may aid in anticipating responses to disturbances such as drought or herbivory.
The bryophyte diversity in northern British Columbia is insufficiently studied. We conducted a bryophyte survey in a 2.2-km2 proposed ecological reserve at the summit of Pink Mountain in the Peace River District of northern British Columbia. Pink Mountain is at the southern periphery of the ranges of several arctic flora species as well as the northernmost reaches of other temperate flora species. The south summit of Pink Mountain has a high floristic diversity coincident with its limestone geology, which provides a more alkaline condition for plant growth than the north summit does. We documented 65 species, including 2 new provincial records for British Columbia (Polytrichumhyperboreum and Tayloria hornschuchii), one red-listed (threatened) species (Tortula systylia), and one blue-listed (at-risk) species (Mnium arizonicum). Polytrichum hyperboreum and T. hornschuchii have affinities to habitats more typical of polar regions. The presence of P. hyperboreum at Pink Mountain represents a southward range extension from 61°33′ N in western North America. Because isolated populations at species distribution limits are likely to be vulnerable to climate change, the establishment of an ecological reserve on the south end of the summit of Pink Mountain is important for the preservation of bryophyte habitat.
The Colorado River in the Grand Canyon holds the largest remaining population of Humpback Chub Gila cypha, an endangered fish endemic to the Colorado River basin. Early surveys in the 1990s found that most Humpback Chub occupied the Little Colorado River and nearby areas in the mainstem Colorado River and were uncommon in the western Grand Canyon (below Kanab Creek, at river kilometer [rkm] 257.2). From 1939 to 2002, the Colorado River was typically inundated by Lake Mead to rkm 407 (at full pool). Since 2000, Lake Mead water levels have declined, and the current inflow is located almost 100 km downstream at rkm 503.1. Thus, the Arizona Game and Fish Department (AGFD) extended its system-wide monitoring downstream to Pearce Ferry rapid (rkm 478.6) in 2011. Electrofishing is relatively inefficient at capturing Humpback Chub, but a small number of captures from 2011 to 2015 in the western Grand Canyon suggested that the Humpback Chub may have expanded its range downstream. Subsequently, hoop nets were added to AGFD system-wide monitoring in 2016 to better describe Humpback Chub distribution. The distribution of Humpback Chub observed in 2016 and 2017 differed from previous descriptions; we documented relatively large numbers of Humpback Chub, including age-0 fish, in the western Grand Canyon and observed the highest catches downstream of Diamond Creek (rkm 389.1). This suggests that a recent range expansion has occurred and that Humpback Chub in the western Grand Canyon do not utilize the Little Colorado River for reproduction and might therefore constitute a new subpopulation.
High selenium (Se) in watersheds can cause detrimental effects to many vertebrate species, but less is known regarding its effects on invertebrates comprising the basis of the food chain. This study addressed the response of a natural community of chironomid (midge) species to Se in 2 high-gradient streams that join to form a sandy-bottom front-range stream known to contain increasing downstream concentrations of Se. We identified a total of 151 species of adult male midges (n = 714) collected in 2007 and 2008 from 14 sites in the Fountain Creek Watershed, Colorado, USA. In the initial analysis, the midge community was assessed for possible effects of Se and pH by using binary sets of 25 variables by means of canonical correspondence analysis (CCA) procedures. Further computations revealed significant relationships between the presence of midges and spring total Se (P = 0.0006, unfiltered water), dissolved Se (P = 0.0006, filtered water), and pore water Se (P = 0.0034, interstitial water in coarse and fine gravels) in the spring season. In the fall, the community showed a significant response to total Se (P = 0.0500), a strong association with dissolved Se (P = 0.0044), and a weaker yet significant association with pore water Se (P = 0.1266). We have not found reports indicating either positive or negative responses of midges to increasing Se in field studies. Although there were no significant associations of midges with lower pH during the spring in any fraction of the water (P = 0.7367, 0.7367, and 0.7469, respectively), there were significant associations to higher pH during the fall in all fractions (P ≤ 0.0100). Mean concentrations of dissolved Se in lower-elevation sites ranged from 2.05 to 9.69 µg/L in the spring and from 2.67 to 18.59 µg/L in the fall; mean pH ranged from 7.5 to 7.8 in the spring and from 8.0 to 8.1 in the fall (2007). The association of silt/clay particles with the occurrence of midges was not significant in any of the waters in the spring or fall. Since some chironomid midges have a tendency to be found in areas exhibiting increasing Se in a downstream gradient in Fountain Creek, would they be found in similar water quality profiles in other watersheds? This possibility warrants serious study in other streams, particularly in the western United States where Se has been entering aquatic food chains of fish, birds, and mammals.
Prepositioned areal electrofishing devices (PAEDs) are used to evaluate microhabitat use by fishes because they minimize fright biases associated with traditional electrofishing techniques (e.g., boat electrofishing). Similarly, fixed underwater videography (FUV) is commonly used to minimize the effect of observers on fish behavior. The specific objectives of this research were to evaluate estimates of taxonomic occurrence and diversity between PAEDs and FUV and determine an appropriate time interval between positioning and electrifying of a PAED to reduce effects of PAED positioning on fish occurrence. Video cameras were positioned instream at 28 locations on the Kootenai River, Idaho, prior to PAED deployment such that the entire immobilization zone of the PAED was captured on camera. Following a 4-min acclimation period, cameras recorded fish behavior approximately 15 min prior to and 20 min following PAED deployment. Electrical current was applied to the PAEDs for 20 s immediately following the FUV procedure, and immobilized fishes were collected and processed. Video footage was subsampled in the laboratory, and fishes in the video were identified and enumerated in 5-s or 20-s intervals. Fixed underwater videography sampled more taxa than PAEDs at any given site. However, fishes sampled with FUV were difficult to identify, and most individuals were classified as “unidentifiable.” Consequently, direct comparisons between FUV and PAEDs are limited. Our results indicate that PAEDs should remain undisturbed for a minimum of 12 min before the equipment is electrified. Both PAEDs and FUV provide an estimate of taxonomic occurrence, but logistical and financial constraints along with project objectives must be considered when selecting between these 2 gear types. Results from this study provide information on the effectiveness of each gear type as it relates to the characterization of riverine fish assemblages at a small spatial scale.
Managing livestock disturbance in riparian zones in a manner that provides economic returns to ranchers while protecting streams is an important aspect of rangeland management on public lands in the western United States. Attempts to balance economic and ecologic outcomes have been made more difficult due to the presence of several salmonid species that are protected under the Endangered Species Act. One approach to proper management of livestock use near streams has been to define the allowable limits of disturbance using 2 metrics, streambank alteration and stubble height. We evaluated 153 stream reaches within the Interior Columbia Basin to determine if these 2 surrogates of livestock disturbance measured after the vegetative growing season were associated with stream conditions important to salmonids evaluated the following summer. We found that each stream habitat attribute that was evaluated (width-to-depth ratio, streambank angle, percent undercut banks, streambank stability, residual pool depth, percent pools, percent pool-tail fine sediments <2 mm, and wood frequency) trended toward lower-quality salmonid habitat as streambank alteration increased or as stubble height decreased. While the strength of these associations were variable, the slopes of the relationships suggest that managing the amount of streambank alteration or stubble height could influence stream conditions within the Interior Columbia Basin. Because improved stream conditions for salmonids corresponded to decreased livestock disturbance, the amount of disturbance allowed in a stream reach will need to reflect management expectations and the environmental setting within the allotment. As a starting point, we suggest the continued application of existing livestock disturbance standards in stream reaches with good habitat conditions, and the specification of more conservative disturbance standards in stream reaches that have degraded habitat conditions.
The northern leatherside chub (Lepidomeda copei) is a cyprinid fish native to the Snake River, Green River, and Bonneville basins of the western United States. Population declines prompted the development of a multistate conservation agreement and strategy, which emphasized the need to reliably delineate its current distribution and monitor its status. To facilitate species monitoring, we developed a quantitative PCR assay to detect northern leatherside chub DNA in environmental samples. The assay consistently detected northern leatherside chub DNA in concentrations as low as 2 copies per reaction and did not amplify DNA of potentially sympatric fish species. The assay amplified a synthetic DNA template representing 3 congeneric species: White River spinedace (L.albivallis), Virgin spinedace, (L.mollispinis mollispinis), and Big Spring spinedace, (L.m. pratensis); however, none of these are sympatric with northern leatherside chub. Field tests of the assay accurately reproduced expected patterns of species occupancy.
Pelagic-broadcast spawning minnows are a reproductive guild of fishes, of which several species occur in the American Great Plains and Southwest. The eggs and larvae of these species drift laterally and downstream, with drift distances varying depending on channel conditions and flow. Persistence or recolonization of these species in upstream reaches must depend on retention of eggs and larvae or upstream dispersal of later life stages, otherwise net downstream displacement of eggs and larvae would result in upstream extirpations. However, only a few individuals of several species have been observed dispersing. Here, we describe 2 direct visual observations of the young-of-year of 4 species of pelagic-broadcast spawning minnows dispersing upstream en masse. In August 2009, we observed Plains Minnow (Hybognathus placitus), Speckled Chub (Macrhybopsis aestivalis), and Rio Grande Shiner (Notropis jemezanus) dispersing upstream. The continuous shoal of fish was >200 m in length and was dispersing upstream at a rate of >1000 fish/min. In July 2017, we observed a continuous shoal of Rio Grande Silvery Minnow (Hybognathus amarus) approximately 1.9 km in length dispersing upstream at a rate between 350 and 1500 fish/min. While such dispersal events are rarely observed, they may be important for maintenance of populations in upstream areas.
On the basis of 86 photographic records, we report the presence of a relatively stable collared peccary (Pecari tajacu) population in the state of Guanajuato, Mexico. These records complement geographical and ecological information for the species along the Gulf of Mexico. The species' predominant habitat is submontane scrub, which corresponded to 54.6% of the records. Family groups (herds) were observed with 3.9 ± 2.9 (mean ± SD) individuals on average. The presence of young indicated 2 reproductive periods per year (March and August). The presence of collared peccaries in the region of greatest biological diversity in Guanajuato provides additional value to the protected areas of the state. This herbivorous species plays a fundamental ecological role as a preferred prey of this area's main predators, such as the jaguar (Panthera onca) and the cougar (Puma concolor). It is important to continue monitoring wild fauna with the purpose of delimiting distributions and estimating populations at the local level.
The nonnative snail Radix auricularia was found at 4 previously unknown locations in Wyoming. At Two Ocean Lake in Grand Teton National Park, R. auricularia was found with trematode infections that were the same cercarial type found in native snails during the same sampling period. Although finding parasitic infections in a nonnative species challenges the enemy release hypothesis, the presence of trematodes in R. auricularia may act to suppress population growth of this snail, thereby emolliating the negative impact this snail may have on native populations. Further research assessing the prevalence of trematode parasites in R. auricularia would aid in understanding whether this nonnative snail harbors parasites across its invasive range, which could have ramifications for parasitism of local waterfowl and wildlife in these habitats.