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Logs provide an important form of coarse woody debris in forest systems, contributing to numerous ecological processes and affecting wildlife habitat and fuel complexes. Despite this, little information is available on the dynamics of log populations in southwestern ponderosa pine (Pinus ponderosa) and especially mixed-conifer forests. A recent episode of elevated tree mortality in these forest types in northern Arizona caused a pulse in log inputs as dead trees broke and fell. We documented changes in these log populations from 2004 to 2009 in an earlier paper. Here, we extended that work to evaluate changes in log abundance and volume between 2009 and 2014, compare trends in log abundance and volume between this period and the preceding 5-year period, estimate overall change in log abundance and volume over the period from 2004 to 2014, and describe temporal relationships between log abundance and changes in populations of snags (standing dead trees) during the study. Trends in log populations differed between forest types. Increases in log abundance were more widespread and larger in magnitude in mixed-conifer forest than in ponderosa pine forest. Over the entire 10-year study period, log abundance increased by 52% and 30% in mixed-conifer and ponderosa pine forest, respectively. Most of that increase occurred in the first 5 years, especially in ponderosa pine forest. Log abundance and volume continued to increase from 2009 to 2014 in mixed-conifer forest, whereas these parameters showed little change in ponderosa pine forest over this period. Log abundance lagged snag abundance, which peaked in 2007 but remained elevated in 2012 relative to pre-2007 levels in both forest types. Thus, log abundance may continue to increase as those snags break and fall. The ultimate magnitude and duration of this drought-mediated pulse in log inputs to these systems thus remains unknown. Understanding how these systems respond to drought-related mortality pulses may aid forest ecologists and managers charged with adapting forest management strategies in an era of changing climate.
Numbers of Common Ravens (Corvus corax) have increased in western North America, and these high abundances are the source of problems throughout the species' range. Little is known about the winter ecology of ravens. We studied a population of ravens in Wyoming during the winters of 2013–2015; our goals were to examine use of landfills for foraging and use of anthropogenic structures for roosting, as well as dispersal patterns of ravens from these landfills in the spring. On average, 22% of radio-marked ravens foraged at landfills on a given day and 68% roosted at anthropogenic sites (e.g. on buildings or underneath bridges) each night. Daily counts at an anthropogenic roost and at the nearest landfill were positively correlated. Decreased temperatures increased raven use of landfills and anthropogenic roost sites. In the spring, radio-marked and GPS-marked ravens (n = 56) dispersed an average of 38 km from the landfills where they were captured. Use of landfills and anthropogenic roost sites in the winter likely contributes to an increase in the number of ravens by improving survival and body condition of breeding-age birds. In the spring, ravens moved outward from these locations, and the area most susceptible to raven damage was localized within a 40-km radius of where ravens wintered.
Urbanization can have significant consequences on local wildlife. While some species can thrive in urban environments, others are often seen as nuisance animals and therefore are either killed by landowners or removed by professionals. Snakes, especially rattlesnakes, represent one such taxon. Here, we analyzed rattlesnake removal data from the city of Phoenix, Arizona, USA, to determine whether the removal data directly correlates with urban expansion. Between 2011 and 2014, over 500 rattlesnakes and over 300 non-rattlesnakes were removed by professionals, with significant removal clusters in the northern Phoenix metropolis. Land cover change analyses showed that all removal sites experienced dramatic changes in the past decade. There was a significant increase in urban land cover and significant decrease in shrub land cover, suggesting a negative impact of urbanization on local snakes.
Animals often migrate to exploit seasonally ephemeral food. Three species of nectar-feeding phyllostomid bats migrate north from Mexico into deserts of the United States each spring and summer to feed on blooms of columnar cactus and century plants (Agave spp.). However, the habitat needs of these important desert pollinators are poorly understood. We followed the nighttime movements of 2 species of long-nosed bats (Leptonycteris yerbabuenae and L. nivalis) in an area of late-summer sympatry at the northern edges of their migratory ranges. We radio-tracked bats in extreme southwestern New Mexico during 22 nights over 2 summers and acquired location estimates for 31 individuals. Both species cohabitated 2 major day roosts that were 30 km apart and in different mountain ranges, and individual bats sometimes moved between the roosts. Sampling was opportunistic and limited, but there were no obvious qualitative differences in observed patterns of movement between species or years, or among sex, age, and reproductive groups. Both species were observed foraging most often in the mountain range that had a relatively higher observed density of presumed food plants (Agave palmeri); when roosting in an adjacent mountain range, bats sometimes commuted >20 km one way to forage. Contrary to evidence indicating these species partition resources farther south in Mexico, our findings suggest that L. yerbabuenae and L. nivalis seasonally share common roost and food resources during late summer in this northern area of sympatry.
Small mammals should be considered in wildlife management decisions because they are an important component of ecosystems. We examined small mammal population abundances (N) on 4 habitat treatment types in Colorado pinyon pine (Pinus edulis)—Utah juniper (Juniperus osteosperma) woodlands on the Uncompahgre Plateau, Montrose, Colorado. We trapped small mammals in Sherman live traps on 4 habitat treatment types—including 2 types of management treatments (chaining, roller chop), sites with high drought-related mortality of pinyon pine, and sites of mature pinyon-juniper (PJ) woodland—on 3 mesas. We modeled detection probability of deer mice (Peromyscus maniculatus) and least chipmunks (Tamias minimus) as a function of 4 treatment types on 3 mesas during 2 trapping periods by using Huggins closed mark-recapture models. A variance components analysis was conducted to obtain abundance shrinkage estimates and to separate spatial process variance from the sampling variance to calculate the percent of variation in abundance estimates explained by treatment type, mesa, and trapping period. Abundance estimates were higher for deer mice and least chipmunks on chaining and roller chop treatment sites than on mature PJ woodland and pinyon pine natural mortality sites. The highest percent of variation in abundance estimates was explained by treatment type for deer mice (33.67%) and least chipmunks (61.45%) and secondarily by mesa for deer mice (21.64%). We calculated species diversity using Shannon's, Simpson's, Pielou's evenness, and species richness indices, and we used analysis of variance to test for significant differences (P < 0.05) in species composition. Species diversity and richness were higher on natural mortality sites than on chaining, roller chop, and mature woodland sites. Our results indicate that chaining and roller chop habitat treatments within PJ woodlands have a positive impact on deer mouse and least chipmunk abundances, whereas natural mortality and chaining treatments have a positive impact on small mammal composition.
Despite a dearth of biological study in the area, the Purgatory Watershed concentrated in southeastern Colorado and northeastern New Mexico is home to a number of unique land formations and endemic organisms. At onetime nonarable land where Dust Bowl storms of the 1930s originated, the Purgatory Watershed is presently home to the Comanche National Grasslands, the Picketwire Canyonlands, and the expansive Piñon Canyon Maneuver Site. The Purgatory Watershed is composed of deep canyons, eroded mesas, and extensive intact shortgrass plains, and is located at a crossroads of the biodiversity of the Southern Rocky Mountains, Great Plains, and Chihuahuan Desert. Here we describe 2 anomalous populations of 2 plant species, prompted by observation of these and several additional, unrelated plants marked by morphologically aberrant forms in this watershed. Specifically, we described morphology of and generated sequence data for Amorpha nana (Fabaceae) and Tetraneuris acaulis (Asteraceae) to assess potential differences between Purgatory populations of these plants and populations from elsewhere across their ranges. Morphometric data from Purgatory and non-Purgatory populations of these 2 unrelated species were collected from specimens housed at herbaria. Similarly, molecular data from Purgatory and non-Purgatory populations of these 2 species, plus near outgroups, were generated from herbarium collections to reconstruct phylogenetic relationships within each species complex. Maximum likelihood bootstrap analysis recovered moderate support for a clade of aberrant A. nana, indicating the presence of a distinct Purgatory lineage of A. nana, which was also supported by our morphological data. In contrast, insufficient phylogenetic signal and morphological results in our Tetraneuris data set yielded unresolved relationships between aberrant and nonaberrant forms. The Purgatory Watershed is a biologically unique region hosting marked biodiversity in numerous groups, despite having been the focus of little prior research.
Ponderosa pine (Pinus ponderosa) forests in the southwestern United States, used by 16 species of bats, are managed with thinning and prescribed fire to restore tree densities and fire regimes to conditions that existed prior to Euro-American settlement. Using 2 approaches (roosting and foraging) to categorize forest habitat for bats, we evaluated how restoration treatments may affect habitat use. We hypothesized that more foraging activity would occur in thinned stands because more species are adapted to open forest, but that more roosts would occur in unthinned stands where snags were unaffected by mechanical treatments and prescribed fire. During the summers of 2006 and 2007, we used acoustic detectors to record call rates of bats as a measure of activity level and compared activity levels among stands that had undergone 3 thinning treatments (light, moderate, and heavy, with 245, 172, or 142 trees per hectare postthinning, respectively) and an unthinned stand as a control (1201 trees per hectare). With radiotelemetry, we located roosts used by reproductive females of 2 common species of forest-associated bats (long-eared myotis, Myotis evotis, and Arizona myotis, Myotis occultus) during summer 2007. We measured roost characteristics at 3 spatial scales (roost, microplot, and surrounding landscape) to contrast between roosts used by Myotis species and randomly selected comparison snags, microplots, and study area landscape. Among thinned and unthinned stands we did not detect a difference in activity levels for all bats (P = 0.2), nor a difference in call rates for Myotis spp. (P = 0.1). However, there was lower activity (P = 0.01) for non-Myotis bats in unthinned compared to thinned stands. This is probably because most non-Myotis species are better adapted to foraging in open forests. Of 24 roosts for long-eared myotis and Arizona myotis, only 31% and 25%, respectively, occurred in thinned stands. Bats selected large-diameter (>68 cm diameter at breast height) ponderosa pine snags with exfoliating bark. Roosts for Arizona myotis were in areas with elements of old-growth structure, whereas roosts for long-eared myotis occurred in areas similar to stratified, midsuccessional, even-aged forest. Managing for large-diameter ponderosa pine snags and a variety of tree densities and age classes will provide roosting and foraging habitat for bats. We found no distinct “best” treatment to recommend overall, likely because of species differences, with some bats better adapted to opencanopy and some to closed-canopy forest. Maintaining diverse habitat will support a diverse bat assemblage.
The disturbance history, plant species composition, productivity, and structural complexity of a site can exert bottom-up controls on arthropod diversity, abundance, and trophic structure. Regulation alters the hydrology and disturbance regimes of rivers and affects riparian habitats by changing plant quality parameters. Fifty years of regulation along the Colorado River downstream of Glen Canyon Dam has created a no-analog, postdam “lower” riparian zone close to the water's edge that includes tamarisk (Tamarix sp.), a nonnative riparian shrub. At the same time, the predam “upper” facultative riparian zone has persisted several meters above the current flood stage. In summer 2009, we used pitfall traps within these 2 riparian zones that differ in plant composition, productivity, and disturbance frequency to test for differences in arthropod community (Hymenoptera, Arachnida, and Coleoptera) structure. Arthropod community structure differed substantially between the 2 zones. Arthropod abundance and species richness was highest in the predam upper riparian zone, even though there was a greater amount of standing plant biomass in the postdam lower riparian zone. Omnivore abundance was proportionately greater in the upper riparian zone and was associated with lower estimated productivity values. Predators and detritivores were proportionately greater in the postdam lower riparian zone. In this case, river regulation may create habitats that support species of spiders and carabid beetles, but few other species that are exclusive to this zone. The combined richness found in both zones suggests a small increase in total richness and functional diversity for the Glen Canyon reach of the Colorado River.
Erigeron lemmonii A. Gray is extremely rare, but not endangered. There are fewer than 1000 individuals, but they compose an apparently stable, heterozygotic, diploid (2n = 18) population. The plants are perennial and endemic to one small location (about 0.5 km2) in Scheelite Canyon, Huachuca Mountains (Cochise County), Fort Huachuca Army Base, part of the Sky Island region, Arizona. Erigeron lemmonii grows from crevices in cliffs, ledges, and rock faces where it can form mats by spreading vegetatively from the roots as they proliferate, especially in microsites where soil accumulates. Our goals were to (1) investigate floral anatomy for reproductive structures (inflorescences, florets, and pollen), (2) record flowering phenology, and (3) determine the species' breeding and mating system. Inflorescence anatomy and development are typical for Erigeron with ray (pistillate) and disc (bisexual) florets. Stigmas of the disc florets do not fully exsert and reflex, though they do present and expose the small (17-m-diameter), spiny, and mostly viable (85%) pollen by pushing it from the anthers below to the florets' entrances during anthesis. Such characteristics are appropriate for entomophily. Erigeron lemmonii has an extended (5–6 month) bimodal (May and August–September) sexual reproductive period. Each capitulum lives about 3 weeks (bud to cypsela-set) and each floret lasts about 5 days. Despite the small population, E. lemmonii is obligately xenogamous and genetically diverse, reliant on insect pollinators to produce wind-dispersed cypselae. It also reproduces clonally. We compare our results to the findings of others on congeners with similar growth habits. Our findings relate to management and conservation of this plant because, to persist, its habitat must support the diversity of pollinating insects on which it is reliant for sexual reproduction.
The northern naked-tailed armadillo (Cabassous centralis) is one of the least known armadillo species. Due to its restricted distribution in Mexico and the few known records of the species, the northern naked-tailed armadillo is considered endangered by Mexican law. Using camera traps, we obtained a new record in Portaceli, Chiapas, an area where the species was not previously recorded. The record was located 75 km north of the previously known range of the species in Mexico, and thus constitutes a range expansion of the species in the country. This record suggests that the species could be present in areas with similar environmental conditions where mammal research has been limited, especially in Tabasco, Mexico, and in Sierra del Lacandón, Guatemala. It is necessary to generate additional information on the species in order to determine the current status of the northern naked-tailed armadillo in Mexico.
Herein we present the first published records (N = 5) of silver-haired bats (Lasionycteris noctivagans) roosting in abandoned mines in Colorado during winter. The records are based on internal surveys of abandoned mines during the winter period from 2004 to 2008. These noteworthy records provide insights into the winter roosting ecology and habitat use of this species in southwestern Colorado.
We documented the occurrence of Eira barbara in the municipalities of Tecpán de Galeana and Petatlán, state of Guerrero, Mexico. Our records represent a 450-km range expansion from the most recent northern occurrences of this species in the Mexican Pacific coast states.