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Noninvasive genetic surveys, often conducted by collecting fecal samples, have become a popular tool for surveying wildlife, but have primarily been applied to species with large and conspicuous scat. Although many small mammals are threatened, endangered, or data deficient, noninvasive genetic surveys have rarely been applied due to the challenges of detecting their inconspicuous fecal pellets. As part of a broader study of the endangered salt marsh harvest mouse (Reithrodontomys raviventris), we developed a noninvasive genetic survey technique for the community of small mammals in their putative range. We designed bait stations to passively collect fecal samples from rodents, and developed a multiplex primer set that amplified unique fragment sizes for salt marsh harvest mice and four other sympatric species. We tested the primer set on positive controls and on fecal pellets collected from bait stations at two regularly monitored field sites known to have very different densities of salt marsh harvest mice. The multiplex amplified DNA from all five species, even when all five species were present in a single sample. A positive species identification was made for all field-collected samples, and 43% of these field-collected samples had multispecies detections. The combination of bait stations and genetic species identification proved to be an effective means of noninvasively surveying small mammals in potential salt marsh harvest mouse habitat. The sampling technique should be applicable to a wide variety of small mammals in other systems.

Closely related species are predicted to have similar fundamental niches, and therefore to compete locally and possibly be constrained to occur allopatrically. Over time, niche differentiation should lead to divergent use of niche axes, such as food or habitat. Most studies of niche divergence or of niche conservatism have focused on multiple species at large spatial scales. We studied two species of closely related chipmunks at two spatial scales in the northern Sierra Nevada. The Long-eared Chipmunk (Tamias quadrimaculatus) and the Shadow Chipmunk (T. senex) are subcryptic species that exhibit extensive geographic overlap in the northern and central Sierra Nevada. Habitat use at the macrohabitat scale was similar, with both species reaching their highest mean abundance in Red Fir (Abies magnifica) forests, but exhibiting divergent secondary affinities. Additionally, macrohabitat associations of T. senex appear to differ from those reported 50 years ago within the same forest, suggesting flexibility in the face of structural habitat changes resulting from forest management actions, climate change, or other factors. At a finer spatial scale, habitat affinities of these chipmunks differed modestly, suggesting that local distribution emphasizes slightly different microhabitat characteristics. We conclude that these species exhibit niche conservatism overall, but whether microhabitat differences reflect competition or niche divergence requires further study. Because T. quadrimaculatus has the smallest geographic range of any Sierra Nevada sciurid, it may be at risk of local extirpation or substantial range restriction in the face of climate change, large-scale high-severity wildfires, and other stochastic threats; the present research sheds light on the ecology of these species, but has important relevance for regional resource managers as well.

Despite increasing awareness of the ecological roles and ecosystem services that bats provide, spatiotemporal patterns in bat abundance and community assembly remain poorly understood outside of select sites in the tropics. We conducted systematic full-spectrum acoustic surveys of bats over the course of a year at eight permanent sites spanning nearly 50 km along Putah Creek, a stream in California’s Central Valley that has been subject to restoration efforts and changes to its in-stream flow regime over the past two decades. We surveyed all sites for 1 week each month. In 158 sampling nights over 11 months, we recorded 157,762 identifiable calls, thereby documenting a rich bat assemblage comprising 15 species from eight genera and two families. Seven species appeared to occur here year-round, whereas six others evidently migrated seasonally, and two were incidental visitors. Species richness and activity diversity were effectively invariant across this 50-km gradient, but assemblage composition varied both spatially and temporally. Spatial patterns suggest species-specific distributions that presumably reflect individualistic habitat preferences and responses to extrinsic factors. Species also varied temporally, with bat activity generally declining in winter, with an unexpected dip in richness and activity in late spring. For the three most commonly detected species, generalized linear models further highlighted the species-specific and individualistic nature of spatiotemporal activity patterns. When integrated with available data from other temperate sites, our results suggest that local species richness is high in temperate riparian systems. Additionally, our observations suggest that species responses to environmental variation are individualistic (e.g., “Gleasonian”) in nature and that local composition varies greatly over spatiotemporal gradients, but that emergent assemblage characteristics do not. The generality of these observations, and the underlying mechanism(s) leading to invariance in emergent characters, warrant further investigation. Similarly, the extent to which greater bat species richness provides complementary ecosystem services (hence, ecological insurance) is of both ecological and economic interest.

The salt marsh harvest mouse (

Mammalogy as a discipline was pursued in Mexico since the mid-17th century. However, Mexican researchers were involved primarily in the mid-20th century, when national scientific journals were established to emphasize research on mammals. In 2010, the Asociación Mexicana de Mastozoología, A. C., initiated the journal Therya. Therya has now completed its first decade of publication, and in this work, we analyze the articles and scientific notes published in Therya, focused on the studies of mammals in Mexican territory, including researchers and institutions, to describe the path that mammalogy has taken in recent years in Mexico. This synthesis therefore serves as a frame of reference for future mammalogy studies. We compiled all papers published in Therya during the period 2010-2019. We built a database gathering information from these publications such as authors, institutions and states of origin, study areas, capture methods, topics and taxa studied. We excluded from the analyses research outside of Mexico. We did a descriptive statistics analysis including mean, proportions, percentage and trends for each and all the sections. Therya has published 181 articles and 52 scientific notes on mammals distributed in Mexico. The majority of authors and institutions were from Mexico City. The states of southeastern Mexico were the most used as a study area, particularly Oaxaca and Chiapas. The orders Carnivora and Cetartiodactyla were the most studied, mainly using indirect methods. Trapping methods were most commonly used for small mammals. The least studied orders were Eulipotyphla, Cingulata, and Pilosa. The most studied topics are ecology, diversity, conservation and distribution. Therya has become one of the most important journals about mammal research in Mexico. Research in mammalogy, as reflected in the pages of Therya, is based in academic institutions with the metropolitan area of Mexico City, reflecting the institutional infrastructure and age, and possibly institutional budgetary factors. The southeast portion of the country is well studied due to the existence of regional institutions, as well as to the concentration of high biodiversity. The least studied regions of Mexico may be the result of a reduced number of research groups and social insecurity. Much research is focused on small mammals, making Sherman traps and mist nets the most used trapping methods; carnivores and cetartiodactyls are the most studied groups, using indirect study methods reducing study costs and effort. Ecology, diversity and distribution are the most studied topics, these studies allow the development of management plans.

Disease may limit recovery of endangered species. We surveyed parasites in the federally endangered salt marsh harvest mouse (SMHM; Reithrodontomys raviventris halicoetes) and sympatric rodents in Suisun Marsh (Solano County, California, USA) from April 2018 through March 2019. We investigated individual SMHM risk factors (age, sex, reproductive status, and body condition) for infection and relationships among the estimated parasite prevalence and season and habitat management (natural tidal habitats versus diked, nontidal habitats). We captured 625 individual rodents, including 439 SMHM, and tested these for infection with Bartonella spp., Borrelia spp., Rickettsia spp., Francisella tularensis, Leptospira spp., Cryptosporidium spp., Giardia spp., and Toxoplasma gondii by PCR. Over one-third (34.6%, confidence interval [CI], 30.2%-39.3%) of SMHM tested positive for at least one parasite. Four percent (CI, 2.8%-6.3%) of SMHM were infected with F. tularensis holarctica, a virulent bacterium that causes mortality in rodents shortly after infection. Additionally, we detected three species of Bartonella (B. henselae, B. rochalimae, B. vinsonii arupensis), Leptospira borgpetersenii serovar Ballum, Cryptosporidium sp. (deer mouse [Peromyscus maniculatus] genotype), Cryptosporidium parvum, Giardia intestinalis, and an unidentified Borrelia sp. The only parasite that was associated with habitat management was Bartonella spp., which was more prevalent in diked than tidal areas. Male SMHM were more likely to be parasitized than females, and individuals in modestly poor body condition were most likely to be infected with Bartonella spp. The estimated sample prevalence of multiple parasites varied by season and by host species. This is the first major parasite assessment in a long-endangered species, and these results will assist managers to incorporate parasitic disease into recovery planning and provide a critical baseline for future investigations, including how climatically induced habitat and species composition changes could alter disease dynamics.

Elevational gradients coincide with expansive climatic gradients and diverse plant and animal communities. We evaluated the small mammal assemblages in eight distinct vegetation types across an elevational gradient in southern California, the Deep Canyon Transect, to determine how assemblage composition changes across the gradient and to identify species with similar habitat associations. Livetrapping efforts (4,800 trap-nights) yielded 1,097 captures of 713 individuals, representing 14 heteromyid and cricetid species. Heteromyids dominated the six lower-elevation vegetation types (< 1,300 m a.s.l.), whereas cricetids dominated the upper end of the gradient. Richness and diversity exhibited bimodal responses to elevation, which do not conform to mid-domain effect null predictions. Canonical correspondence analysis revealed that 75% of the variation in small mammal abundances was explainable by habitat characteristics, and cluster analysis grouped small mammals into three ecologically distinct groups based on their habitat associations. One contained only Chaetodipus penicillatus, while the others were comprised of low- and high-elevation species, respectively. The low-elevation species exhibit unusual levels of sympatry (and syntopy) among closely related species of pocket mice (Chaetodipus). Further efforts should investigate the mechanisms of coexistence for Chaetodipus species with nearly identical associations and seasonal effects on richness and diversity. Repeated surveys of entire gradients such as the Deep Canyon Transect will help refine our understanding of temporal dynamics of community assemblage and diversity.

In hibernating squirrels, the amount of energy stored as fat may influence several important demographic traits, but is difficult to quantify in living animals. Thus, several non-destructive indices of body condition are used, including simple indices that use body mass and scaled indices that correct body mass for structural size. However, the accuracy of these indices for hibernating squirrels is poorly known. We used measurements of total body electrical conductivity (TOBEC) from adult female Golden-mantled Ground Squirrels (Callospermophilus lateralis) to characterize body composition (lean mass versusfat mass) and condition (fat stores) at multiple stages in the circannual cycle. Body mass explained a high proportion of the variation in fat mass during the emergence and pre-hibernation stages, but less during the reproduction stage. Contrary to expectation, correcting for structural size did not markedly improve the condition index. Our results suggest that body mass is a good estimate of body condition during the periods of emergence and pre-hibernation fattening, and therefore may be useful to predict important components of fitness such as reproductive success and overwinter survival.

The study of mammals has promoted the development and testing of many ideas in contemporary ecology. Here we address recent developments in foraging and habitat selection, source–sink dynamics, competition (both within and between species), population cycles, predation (including apparent competition), mutualism, and biological invasions. Because mammals are appealing to the public, ecological insight gleaned from the study of mammals has disproportionate potential in educating the public about ecological principles and their application to wise management. Mammals have been central to many computational and statistical developments in recent years, including refinements to traditional approaches and metrics (e.g., capture-recapture) as well as advancements of novel and developing fields (e.g., spatial capture-recapture, occupancy modeling, integrated population models). The study of mammals also poses challenges in terms of fully characterizing dynamics in natural conditions. Ongoing climate change threatens to affect global ecosystems, and mammals provide visible and charismatic subjects for research on local and regional effects of such change as well as predictive modeling of the long-term effects on ecosystem function and stability. Although much remains to be done, the population ecology of mammals continues to be a vibrant and rapidly developing field. We anticipate that the next quarter century will prove as exciting and productive for the study of mammals as has the recent one.

Many wildlife species rely on unique features of trees during daily activities and fundamental parts of their life cycle. The fisher (Pekania pennanti) is a forest-dwelling carnivore of conservation concern in western North America that uses unique habitat elements as refuges during resting bouts and for reproduction. Prior to this study, little was known about the fine-scale habitat used during reproduction at the southernmost extent of the fisher’s range. Between 2007 and 2015, we attached radio-collars to 55 male and 72 female fishers in the southern Sierra Nevada and documented resting locations of males on 216 occasions (196 structures) and females on 824 occasions (737 structures). Beginning in 2008, we also monitored females over 8 reproductive seasons, confirming 45 females at dens and documenting 95 natal dens (83 structures) and 206 maternal dens (192 structures). We established 3 comparisons to guide our assessment of fine-scale habitat: resting males versus resting females, natal dens versus maternal dens, and resting fishers (both sexes) versus denning fishers (all dens). We expected the need for physical security and thermal protection in combination with morphology, predation risk, and aspects of reproductive ecology would influence patterns of use. Both sexes used a variety of microsites for resting, but females selected tree cavities most frequently (47%) while males used branch platforms most often (39%). For resting structures, live conifers were used most often by both sexes (males 44%, females 34%), but live hardwoods (males 16%, females 28%) and conifer snags (males 16%, females 22%) were also important. Comparing natal and maternal dens, we found that cavity microsites used early in the den season tended to be higher than those used later, and large live hardwoods comprised roughly half of all natal (46%) and maternal (51%) den structures. For resting versus denning, we found that large diameter hardwoods were an important source of cavities for both activities, live conifers used for denning were larger than those used for resting, and den structures tended to be on steeper slopes than rest structures. White fir (Abies concolor), California black oak (Quercus kelloggii), and ponderosa pine (Pinus ponderosa) were selected most often by both sexes for resting. In contrast, denning females relied on California black oak (55%), but also used white fir (24%) and incense cedar (Calocedrus decurrens; 12%). As noted in studies further north, our findings highlight the value of large trees with decay to support fisher reproduction and daily refugia.

Scavenging is a common phenomenon, particularly amongst carnivorous vertebrates. By consuming carrion, vertebrate scavengers reduce resource availability for both pathogenic bacteria and their insect vectors. We investigated the ability of wild vertebrate scavengers to control agents of human diarrheal diseases (specifically Salmonella spp. and Shiga toxin-producing Escherichia coli [STEC]) in oil palm plantations in Sabah (East Malaysia), and the existence of spillover effect whereby additional vertebrate scavengers from adjacent forest patches result in greater disease control in plantation sections near these forest edges. Experimental carcasses were removed by common scavengers (Varanus salvator, Canis lupus familiaris, and Viverra tangalunga) at different time points, and this determined the length of time that the carcasses persisted in the environment. The amount of pathogenic bacteria on the surfaces of filth flies collected above the experimental carcasses was positively correlated to the duration of carcass persistence, and reduction in pathogenic bacterial abundances was largely due to carcass consumption by these vertebrate scavengers. Instead of a predicted positive spillover effect (greater scavenger activity near forest edges, hence reduced pathogen abundance), we detected a weak inverse spillover effect in which STEC counts were marginally higher in plantation sections near forest patches, and human hunting along the forest-plantation boundaries could explain this. We propose that making oil palm plantations scavenger-friendly could yield great human health benefits for the millions of workers employed in this rapidly-expanding industry, without drastically changing current management practices.

The matorral or Mediterranean scrub biome occurs within a narrow band of central Chile between approximately 30 and 38°S latitude. Bounded on the east by the Andean Cordillera and on the west by the Pacific Ocean, the area is characterized by a winter-wet, summer-dry climate, generally frost-free winters, and prolonged summer drought. A diverse flora includes many sclerophyllous shrubs, some drought-deciduous ones, and an herbaceous understory during winter and spring months. However, within the latter, exotic species which have become naturalized now make up a substantial proportion of the ephemeral flora. Matorral perennial shrub vegetation displays considerable endemicity, and is structurally convergent with Mediterranean scrub in California, Spain, and the Mediterranean Basin. Among higher vertebrates, herptiles, birds and small mammals exhibit broad geographic ranges in the matorral and lower species turnover between habitats (β-diversity) than in other Mediterranean scrub areas. Despite low taxonomic affinity, similar to perennial shrubs, there is convergence in major body types, feeding guilds and foraging techniques. Due to anthropogenic disturbance including clearing, fire, and extensive overgrazing/browsing, there are relatively few intact examples of undisturbed matorral left, and greater effort needs to be expended to preserve this highly unique biome. Long-term studies at a thorn scrub site on the northern edge of the matorral suggests that altered rainfall patterns have led to changes in the small mammal assemblage composition. Over time, such effects may also become manifest in the central Chilean matorral.

© Published by Oxford University Press on behalf of American Society of Mammalogists 2018. Quantifying reproductive parameters is essential for developing effective conservation plans for species of concern; however, studying reproduction in wild settings can be challenging and local data are frequently unavailable. The fisher (Pekania pennanti) is an elusive forest-dwelling carnivore of conservation concern that occurs across much of boreal North America and reaches the southernmost limit of its distribution in the southern Sierra Nevada (SSN) in California. Data on fisher reproduction in this region are limited and applicability of parameters from other areas is uncertain. To clarify how fisher populations in the SSN compare with those elsewhere in North America, we conducted a comprehensive review of available literature on reproduction throughout the species' range in North America. We then compared findings from the review with data we collected during 7 years in the SSN, focusing on the proportion of females reproducing, litter size, and the parturition date. On average across the fisher's range, the proportion of adult females that reproduced was 0.71 (range: 0.40-1.00; n = 16 studies), litter size was 2.5 (range: 1-4; n = 16 studies), and parturition occurred on 25 March (range: 3 March-17 April; n = 16 studies). In our study area, we tracked 42 adult female fishers, 35 of which reproduced and used 257 reproductive dens (74 natal, 175 maternal, 8 early failures); 0.86 of our females attempted denning (range: 0.79-1.0; n = 93 opportunities) and 0.75 were successful (range: 0.64-1.0; n = 91 opportunities monitored through the den season). Mean litter size was 1.57 (range: 1-3; n = 75 litters) and mean parturition date was 30 March (range: 17 March-12 April; n = 69 natal dens initiated). Female fishers at the southern limit of their distribution in the SSN reproduced at a rate comparable to or higher than elsewhere in North America, but average litter size was the lowest reported for the species. Female fishers in the SSN gave birth at similar or later dates than elsewhere in their range. We explore factors that might explain patterns of variation in fisher reproductive parameters and discuss conservation implications of our findings.

International audience; Long-term studies on rodents have been conducted for longer periods (up to 70 years) and more generations (upto 88 generations) than for most other mammalian taxa. These studies have been instrumental in furthering ourunderstanding of ecophysiology, social systems, and population and community processes. Studies on Africanstriped mice (Rhabdomys pumilio) revealed that basal blood glucose levels span a far greater homeostatic rangethan previously thought. Studies on American red squirrels (Tamiasciurus hudsonicus) demonstrated howendocrine pathways underlying phenotypic plasticity allow individuals to respond to different environments.Long-term studies on African striped mice, marmots (Marmota), tuco-tucos (Ctenomys sociabilis), and degus(Octodon degus) revealed that ecological constraints on dispersal are drivers of group formation in some speciesbut not others. Social flexibility, when the social system of an entire population can change due to individualschanging their social tactics, has been demonstrated in striped mice. Long-term studies on prairie voles (Microtusochrogaster) found that males and females often live in pairs, leading to subsequent studies of the neuralmechanisms underlying social monogamy. Long-term studies on other arvicoline rodents contributed more toour understanding of the factors influencing population dynamics than studies on any other mammalian order.While food availability and predation have been identified as factors influencing population dynamics, no singlefactor alone drives population dynamics in any species. We encourage researchers to incorporate manipulativeexperiments into long-term studies and to take integrative approaches to inform cross-disciplinary theory.

The riparian brush rabbit Sylvilagus bachmani riparius is restricted to areas of dense cover along rivers and tributaries in the Central Valley of California, USA, and is considered endangered under the U.S. Endangered Species Act. An approved recovery plan for this subspecies recommended establishment of three additional self-sustaining populations within its historical range. Concurrent with habitat restoration efforts that included revegetation of levees and provision of flood refugia, we reintroduced 325 captive-bred individuals to the San Joaquin River National Wildlife Refuge between July 2002 and July 2005, and monitored their survival with radiotelemetry. Using available survival estimates and estimated reproductive parameters, we developed a population viability analysis model to determine the risk of extinction of the reintroduced population under a series of alternate scenarios including different release strategies. All model scenarios resulted in high probabilities of extinction over 20 y in the absence of either ongoing supplementations or significant improvements to vital rates. Extinction risks over 20 y appeared independent of initial release strategies. The risk of extinction remained high (>99%) even when the initial founder population was supplemented with captive-bred brush rabbits for up to 10 y. Supplementing the population annually for the entire 20-y period would be required for the population to persist given current estimates of vital rates. These results suggest that the reintroduced population is not self-sustaining and continued releases will not provide the anticipated long-term benefits. Additionally, our understanding of the integral components of habitat and potential limiting factors should be refined to address their influence on demographics and the cause of brush rabbit declines at the release site in a comprehensive way. These results underscore the importance of viability analyses and developing testable hypotheses about potential limiting factors early in reintroduction efforts to more efficiently guide data-gathering and monitoring criteria, identify data deficiencies, and refine reintroduction techniques in the early stages of management.

Plant facilitation is now recognized as an important process in severe environments. However, there is still no agreement on how facilitation changes as conditions become increasingly severe. The classic stress gradient hypothesis (SGH) predicts a monotonic increase in facilitation, which rises in frequency as conditions approach the extreme end of the environmental gradient. However, few studies have evaluated the validity of the SGH at the community level, the level at which it was formulated. Moreover, few studies have tested the SGH at either extreme of the gradient, and very few have excluded the effect of livestock on community response to stress. In line with the SGH, we hypothesized that several spatial pattern summary statistics would change monotonically from the least to the most arid sites, indicating increasingly aggregated patterns. In this study, we performed an evaluation of the SGH both within communities of shrub species and across a large portion of the Atacama Desert, and we isolated the abiotic component of the SGH. Our environmental gradient covered an extreme aridity gradient (

Desertification and climate change are degrading large areas of arid and semiarid habitat in many regions. In response, many countries have implemented revegetation programs, commonly using Atriplex nummularia, native to Australia. Although not intrinsically targeted at habitat restoration, these programs aim to restore (stabilize) erosional processes and provide livestock forage (usually goats, sheep). Few investigators have assessed the utility of these novel habitats for native fauna. In a recent, extensive survey of small mammal communities in lands revegetated with A. nummularia in north-central Chile, we captured a single animal, the marsupial (Thylamys elegans). We also captured no birds in our live traps and saw numerous darkling beetles in traps. These striking results contrasted with data from a nearby ungrazed park with natural vegetation where 10 small mammal species are known with total abundances ranging from 15 to 80 animals in similar sampling efforts. These revegetated lands provide poor habitat for native mammals, and we argue that revegetation efforts should include proactive risk assessment and cost-benefit analyses in a structured decision-making framework. In addition, managers should target increased plant species diversity to support broader biological diversity in addition to the need to control erosion. Although our work has focused on revegetation with Atriplex, numerous other plant species have been intentionally introduced to arid lands, usually for economic reasons; many of these, like Atriplex, have unintended consequences for native biota.

In 1989, we initiated a long-term field experiment in a semiarid thorn scrub community in north-central Chile. We posited that biotic interactions, particularly predation, interspecific competition, and herbivory assumed a primary top-down role in affecting small mammals and annual plants here. Using a multi-factorial design we selectively excluded vertebrate predators (principally carnivores and raptors) and a large small mammal herbivore, the degu (Octodon degus), from replicated 0.56 ha exclosures located in a valley near the coast in Bosque Fray Jorge National Park. Evidence initially supported effects of predator exclusion on O. degus but not for other small mammals in the assemblage (e.g., Phyllotis darwini, Abrothrix olivaceus). Subsequent years of monitoring have documented that predation has temporary effects on degu numbers, but that populations of this and other small mammals are much more strongly influenced by environmental bottom-up factors (i.e., rainfall). Further, our experimental manipulation has provided no evidence for negative interspecific competition effects on numbers of any small mammal in this assemblage. Degu exclusions, however, have had negative indirect effects on exotic annuals; native annuals appear to outcompete exotics especially during drought years The effect is magnified in all-small mammal exclusions. Since about 2002, selective exclusions of lagomorphs and small mammals have resulted in changes in cover of some perennial shrubs. Also notable has been a fundamental shift in the small mammal composition following the last major El Niño Southern Oscillation (ENSO) event in 2000?2002; degus now comprise a majority of small mammal biomass in the assemblage, and their numbers have become more stable and less temporally variable. This appears to have been caused by a shift in rainfall periodicity from strong interannual fluctuations in response to periodic ENSOs, to a more equitable pattern with more consistent annual rainfall. This represents one of the first documented cases of system-wide biotic phase shifts to a relatively modest change in rainfall regime. This may be indicative of ongoing climate change in the Chilean semiarid region, and we expect that further changes in the community will occur if those trends continue. Fil: Meserve, Peter L.. University of Illinois; Estados Unidos Fil: Kelt, Douglas A.. University of California; Estados Unidos Fil: Gutiérrez, Julio R.. Universidad de La Serena; Chile Fil: Previtali, Maria Andrea. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias. Departamento de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina Fil: Milstead, W. Bryan. U.S. Environmental Protection Agency; Estados Unidos

In 2003, we initiated a sampling protocol for arthropods as part of long-term field experiment in a semiarid thorn scrub community in north-central Chile. We utilized pitfall and Malaise traps to sample terrestrial and volant arthropods, respectively. Inventories were conducted for 4 days and nights monthly. We posited that arthropod abundance and biomass would track environmental changes such as high rainfall often due to El Nino Southern Oscillations (ENSOs). Peaks in both abundance and biomass for terrestrial and volant arthropods were in similar months (spring–early summer; August–November); arthropods also tracked high rainfall years in 2004, 2006, and 2011, due mostly to increases in a few dominant groups, i.e., tenebrionid beetles (Coleoptera) in terrestrial sampling, and moths (Lepidoptera: Noctuidae, microlepidoptera) in aerial sampling. However, the same groups increased dramatically in 2008 which was a below-average rainfall year. Numerical decreases in late summer-fall months (January–April) were more abrupt for terrestrial arthropods than for volant ones. Both terrestrial and volant arthropods reached their lowest levels in winter months (June–July). Some evidence suggests long-term shifts in the composition of volant taxa. Arthropods likely are important prey items for insectivorous reptiles (i.e., lizards), birds, and an insectivorous small mammal, the elegant mouse opossum ( Thylamys elegans ), and future efforts are being directed towards examining the evidence for correlated changes in those consumers with arthropod abundance and biomass.

Models of plant–plant interactions suggest that nurse plants are critical for the maintenance of biodiversity and ecosystem functions in arid and semiarid lands. At the community scale, however, empirical support of this idea is limited and context-dependent. Following on a preliminary work which suggested that a dominant shrub in north-central Chile ( Porlieria chilensis ) had nurse plant effects, we tested the effects of this and two other shrubs ( Adesmia bedwellii and Proustia cuneifolia ) on community biomass production, species density, and species composition of ephemeral plants in the semiarid scrub of the Bosque Fray Jorge National Park (Chile) over four consecutive years. We tested for main and interactive effects of shrubs and precipitation on total biomass production and species density of ephemeral plant communities using Generalized Linear Mixed Models (GLMM). To analyze the effects of shrubs and precipitation on species composition we used Canonical Correspondence Analysis (CCA) and t-value biplot analysis. Total biomass production increased significantly with precipitation and was consistently lower beneath shrub canopies, particularly under A. bedwellii and P. chilensis . Although ephemeral plant species density generally was higher in open areas, differences between open and shrub canopy samples diminished with increasing precipitation. Finally, despite significant differences in ephemeral plant species composition between open areas and shrub canopies, we found no evidence of shrub species-specific effects. In conclusion, our results do not support a classical nurse plant syndrome in the semiarid scrub of the Bosque Fray Jorge National Park although shrubs can increase local diversity by favoring some ephemeral plant species that are absent in open areas.

Patterns in rainfall and soil water availability are considered to be the main drivers governing arid and semiarid ecosystems. While the mechanisms by which water limits aboveground net primary production has been widely explored, few long-term studies have examined interactions between precipitation, soil resources, plant communities, and soil microbial communities; these may be critical to understanding soil biogeochemical cycles and above- and belowground interactions. We capitalized on a long-term biotic manipulation (exclusion of small mammal herbivores from replicate plots) and long-term variation in rainfall to assess how precipitation, small mammals, and shrub cover act directly and interactively to influence the spatial and temporal distribution of soil microorganisms, a key first step to understanding soil biogeochemical cycles. We measured the abundance of arbuscular mycorrhiza (AM), soil fungi, soil bacteria, and soil physicochemical characteristics over 10 consecutive years in a semiarid thorn scrub community in north–central Chile; we sampled two microhabitats (under shrub cover, and in open spaces between shrubs colonized by ephemeral plants), and in plots with or without the presence of native small mammals, the main herbivores in this environment. Annual rainfall ranged widely (11–356 mm) in this period and was the primary factor affecting abundance of AM root colonization and soil microbes. While the percentage of root length with AM was higher in dry compared to wet years, free-living soil bacteria and fungi were more abundant during wet years. All microorganisms were more abundant in the resource islands beneath the shrubs compared to open microhabitat between shrubs, although the relation between soil biota and the concentration of some particular nutrients was negative. These patterns were modulated by the presence of small mammals, which enhanced root colonization by AM fungi, particularly for ephemeral plants, but which were negatively associated with soil fungi abundance. The abundance of soil bacteria showed a more complex response to the presence of small mammals and was dependent on microhabitat and year. The spatial and temporal heterogeneity of soil resources and the activity of small mammals are important modulators of subterranean biotic responses to rainfall, the primary factor affecting soil microbiota abundance in this semiarid ecosystem.

The avifauna of Chile is relatively depauperate, comprising 469 extant species, of which 213 are terrestrial. However, the Coquimbo Region presents a broad ecological transition from the hyperarid Atacama Desert to the north, and the more mesic Chilean Mediterranean region of central Chile, resulting in relatively high species diversity. Approximately 130 species are found here, 8 of which are endemic to Chile although not to this region. Bosque Fray Jorge National Park is a 9959 ha Biosphere Reserve dominated by matorral habitat and hosting up to 123 bird species. Through avian surveys and banding over nearly a decade we have documented 63 terrestrial species and discerned predictable seasonal and interannual structure to avian assemblages, at least through an extended dry period. Recent studies in the matorral habitats of the park indicate seasonal patterns that fall into 4 patterns: year-round residents, winter visitors, summer breeders, and transients. Short-term banding studies demonstrate co-occurring wintering and breeding cohorts among species of Sierra-finches (Phrygilus) in the park; such assemblages and dynamics are reminiscent of North American Mediterranean avian assemblages and pose interesting ecological comparisons. In this period of surveys there appears to have been a gradual transition of the avifauna that may be a response to anthropogenic influence and/or climate change. Research on the foraging behavior of 2 insectivorous species indicate that one of these is convergent on better-known North American taxa while the other clearly is not; these efforts suggest useful avenues for further comparative research. A remarkable coevolutionary association between the Chilean Mockingbird (Mimus thenca) and endoparasitic mistletoes (Tristerix) provides insight into potential convergent ecologies in desert regions with different evolutionary histories. Less than 1% of the park comprises temperate forest remnants that subsist due to extensive water input from fog. Research in these remnants has emphasized the role of habitat fragmentation on avian assemblage composition and on reproductive ecology by forest-dependent species. The avifauna here comprises a subset of that found in intact Valdivian rainforest to the south, and forest remnant size alone explains over 90% of the variation in species numbers. One species has been particularly well studied; the Thorn-tailed Rayadito (Aphrastura spinicauda) is more abundant and has higher nestling survival in larger fragments. We summarize other work on stress responses and variation in song structure in this species. Finally, the role of birds in tree recruitment here has important implications in the face of a recent history of reduction in sizes of forest remnants; numerous birds consume the fruit of the dominant tree, olivillo (Aextoxicon punctatum), but they fail to promote successful recruitment because they defecate viable seeds in locations that provide poor survival of seedlings. Ornithological research in Chile is undergoing a modest renaissance, and while dryland avifaunas are characterized more by what is not known and has yet to be studied than by actual ecological understanding, they provide a baseline for many exciting studies ranging from natural history to the role of migration to comparative dynamics of independent lineages in North and South America.

Scientists are increasingly interested in the evolutionary responses of organisms to unpredictable, variable, and extreme climate changes. In semiarid environments, inter-annual variability in the frequency and amount of rainfall affects both the growth and recruitment of plant species, especially annuals. In these inherently variable environments, individual selection should favor demographic responses that spread the risk of mortality over time and enhance long-term reproductive success (i.e., bet-hedging strategies). However, the same processes that allow the persistence and recruitment of native species could facilitate the introduction and establishment of exotics. We assessed whether native and exotic annuals in semiarid Chile displayed similar or contrasting bet-hedging traits, and discuss mechanisms of coexistence of both types of species and their demographic variation under interannual rainfall variability driven by El Nino Southern Oscillation (ENSO). We analyzed a proxy of long-term fitness, i.e., the variability of seed density over 17 years, for the two most common native and two exotic annual plant species present in the study area. We experimentally tested whether the quality of the maternal environment (soil water supply in a given year) had an extended effect (e.g. the next year) on the proportion of seed germination or on the mean and/or variability of seed size and seed dormancy. Results showed that native and exotic species in this annual plant assemblage displayed contrasting bet-hedging strategies as evolutionary responses to variable rainfall. Although rainfall variability promotes the evolution of bet-hedging strategies, the nature of these strategies varies across species, presumably to minimize competitive exclusion. In semiarid Chile, the success of two exotic ephemerals that are components of a diverse community of native annual species seems to reflect bet-hedging germination strategies that complement rather than compete with those expressed in dominant natives.

Author(s): Smith, Katherine R.; Riley, Melissa K.; Barthman–Thompson, Laureen; Statham, Mark J.; Estrella, Sarah; Kelt, Douglas | Abstract: [Abstracts are not presented for essays. -The SFEWS Editors.]

Author(s): Smith, Katherine R.; Riley, Melissa K.; Barthman–Thompson, Laureen; Woo, Isa; Statham, Mark J.; Estrella, Sarah; Kelt, Douglas A. | Abstract: The salt marsh harvest mouse (SMHM, Reithrodontomys raviventris) is an endangered species, endemic to the San Francisco Estuary. Despite being protected for almost half a century and being included in a large number of recovery, restoration, and management plans, significant data gaps hinder conservation and management of the species, a challenge further complicated by developing threats such as climate change. In this review, we present the current state of knowledge; highlight research gaps on habitat requirements and distribution, taxonomic status and genetic structure, physiology, reproduction and demographics, population dynamics, and behavior and community interactions; and present an overview of threats to the species. Our review indicates that substantial data gaps exist; although some aspects of SMHM ecology, such as habitat use, have been addressed extensively, others, such as the effects of environmental contamination, are largely unaddressed. We suggest that conservation and restoration-planning processes consider experimental approaches within restoration designs to address these deficiencies. Continued investment in basic and applied SMHM ecology to collect baseline and long-term data will also be beneficial. Additionally, further coordination among managers and researchers can facilitate more effective responses to uncertainties and emerging threats, especially climate change, which threatens the SMHM and its habitat throughout its range.

This is a data paper for the Portal Project, a long-term ecological study of rodents, plants, and ants located in southeastern Arizona, U.S.A. This paper contains an overview of methods and information about the structure of the data files and the relational structure among the files. This is a living data paper and will be updated with new information as major changes or additions are made to the data. All data - along with more detailed data collection protocols and site information - is archived at: https://doi.org/10.5281/zenodo.1215988 . Background and Summary Long-term studies play a key role in ecology by providing unique and often foundational insights into how nature operates (Lindenmayer et al 2012; Hughes et al 2017a). Insights from long-term studies have advanced our understanding of the rapidity of species evolution (Boag and Grant 1981; Grant 1985; Arbogast et al 2006) and contributed to the development of ecological theories (Hubbell 2001) and the discovery of anthropogenic impacts on nature (Hughes et al 2017b). Despite the importance of long-term data for understanding how ecosystems and processes change over time, less than 9% of studies in ecology use data collected for more than a decade (Estes et al 2018). In ecology, data collection for a typical study spans fewer than 3 years (Tilman 1989, Estes et al 2018). Without institutional support (e.g. NSF-funded Long-Term Ecological Research sites), long-term projects can be difficult to maintain, vulnerable to both the vagaries of funding and to the longevity and interest of the scientist running it. Because long-term data is difficult to collect, there is often resistance by its collectors to making it publicly available (Mills et al 2015). Thus long-term data is highly valuable but also less available than other types of data. This data paper describes a publicly-available, long-term study of a Chihuahuan Desert Ecosystem near Portal, Arizona in the United States (aka the Portal Project). Started in 1977, the Portal Project encompasses over 40 years of ecological research, involving both short-term and long-term experiments and monitoring of a variety of different taxa (rodents, plants, and, for many decades, ants). These data have been used in over 100 scientific publications studying competition (e.g., Munger and Brown 1981), granivory (e.g., Chen and Valone 2017), community dynamics (e.g., Ernest et al 2008), and the long-term reorganization of the ecosystem in response to habitat conversion (e.g., Brown et al 1995). Data can be downloaded from Zenodo ( https://doi.org/10.5281/zenodo.1215988 ). The goal of this data paper is to provide an overview of the study, our available data and its structure, and the general data collection and data entry/quality assurance/quality control processes for the different data types. Detailed protocols for data collection and curation are in the metadata associated with the archived data.

The Biological Survey Unit (BSU) is administered by the U.S. Geological Survey (USGS) and located in the Smithsonian Institution's National Museum of Natural History (NMNH) ([ 1 ][1], [ 2 ][2]). Since 1889, the BSU has managed the North American collections of non-fish vertebrates. The proposed

Managing pest species in urban and suburban areas is challenging, and contraception may provide a socially acceptable and effective management option for many species. The immunocontraceptive vaccine, GonaCon, effectively inhibits reproduction in many species of wildlife, but the behavioral effects are not yet well understood. Contraceptive-induced changes in behavior could raise animal welfare concerns and alter survival and reproductive rates in populations. These vital rates frequently are incorporated in population models to predict the population-level efficacy of contraception. Thus, understanding the behavioral impacts of contraception is necessary to accurately predict population-level effectiveness of contraception and to protect animal welfare. We investigated the behavioral effects of GonaCon on eastern fox squirrels (Sciurus niger), a pest species that has invaded much of the western United States, caused widespread damages to human infrastructure, and threatened native western gray squirrels (S. griseus). We used field observations to measure time-activity budgets and dominance, open field trials to measure exploratory behavior, and mirror image stimulation to measure aggression because GonaCon could alter these behaviors. Contrary to our predictions, we failed to detect any significant effects of GonaCon on any of these behaviors. Our results, combined with a previous study finding that GonaCon is highly effective at inhibiting reproduction in fox squirrels, indicate that GonaCon may be a viable control method for fox squirrels and that behavioral changes affecting the demographic parameters are unlikely to undermine population models used to predict the effectiveness of GonaCon. © 2015 The Wildlife Society.

Understanding the nature of faunal assembly and community structure remains central to ecology. Research in North American deserts and some tropical forests provides evidence of energetic compensation and zero-sum dynamics, suggesting that species in some natural assemblages may be replaced with limited impact on ecosystem function. Experimental removal of a dominant small mammal (degu, Octodon degus) from replicate plots in semiarid coastal thorn-scrub habitat in north-central Chile revealed no evidence for energetic or functional compensation; energy consumption remained significantly lower on degu exclusions relative to control plots after 17 years of exclusion. This occurred in spite of the fact that the geographic species pools for South American sites generally are similar in size to those of most North American sites (mean and median number of species, 16.3 and 21.5 vs. 21.0 and 20, respectively). A macroecological assessment of energetically equivalent species at 394 arid sites in North America, t...

Fire is a natural, dynamic process that is integral to maintaining ecosystem function. The reintroduction of fire (e.g., prescribed fire, managed wildfire) is a critical management tool for protecting many frequent-fire forests against standreplacing fires while restoring an essential ecological process. Understanding the effects of fire on forests and wildlife communities is important in natural resource planning efforts. Small mammals are key components of forest food webs and essential to ecosystem function. To investigate the relationship of fire to small mammal assemblages, we live trapped small mammals in 10 burned and 10 unburned forests over 2 years in the central Sierra Nevada, California. Small mammal abundance was higher in unburned forests, largely reflecting the greater proportion of closed-canopy species such as Glaucomys sabrinus in unburned forests. The most abundant species across the entire study area was the highly adaptable generalist species, Peromyscus maniculatus. Species diversity was similar between burned and unburned forests, but burned forests were characterized by greater habitat heterogeneity and higher small mammal species evenness. The use and reintroduction of fire to maintain a matrix of burn severities, including large patches of unburned refugia, creates a heterogeneous and resilient landscape that allows for fire-sensitive species to proliferate and, as such, may help maintain key ecological functions and diverse small mammal assemblages.

A principal challenge of federal forest management has been maintaining and improving habitat for sensitive species in forests adapted to frequent, low- to moderate-intensity fire regimes that have become increasingly vulnerable to uncharacteristically severe wildfires. To enhance forest resilience, a coordinated landscape fuel network was installed in the northern Sierra Nevada, which reduced the potential for hazardous fire, despite constraints for wildlife protection that limited the extent and intensity of treatments. Small mammal and songbird communities were largely unaffected by this landscape strategy, but the number of California spotted owl territories declined. The effects on owls could have been mitigated by increasing the spatial heterogeneity of fuel treatments and by using more prescribed fire or managed wildfire to better mimic historic vegetation patterns and processes. More landscape-scale experimentation with strategies that conserve key wildlife species while also improving forest resiliency is needed, especially in response to continued warming climates.

Effective restoration of threatened or endangered species requires understanding of basic ecological requirements such as habitat selection and home range needs. The endangered riparian brush rabbit (Sylvilagus bachmani riparius) occupies areas of dense, brushy cover along streamside communities in the San Joaquin Valley of California, but over 93% of this habitat has been lost to urban and agricultural development. We released over 325 captive-born rabbits at the San Joaquin River National Wildlife Refuge (Refuge) between July 2002 and July 2005, and we monitored 312 of these rabbits via radiotelemetry to assess spatial and habitat selection. Home ranges and core areas were similar among males and females, and were larger in the breeding season than during the nonbreeding season. Perhaps reflecting a growing population, home range estimates decreased in size over the duration of the study. Animals moved in response to a wildfire in July 2004, but home range area was similar in 90-day pre- and po...

South America spans about 44° latitude, covers almost 18 million km(2) , and is second only to Africa in continental mammal species richness. In spite of this richness, research on the status of this fauna and on the nature and magnitude of contemporary threats remains limited. Distilling threats to this diverse fauna at a continental scale is challenging, in part because of the limited availability of rigorous studies. Recognizing this constraint, we summarize key threats to small mammals in South America, emphasizing the roles of habitat loss and degradation, direct persecution, and the increasing threat of climate change. We focus on three regional 'case studies': the tropical Andes, Amazonia and adjacent lowland regions, and the southern temperate region. We close with a brief summary of recent findings at our long-term research site in north-central Chile as they pertain to projected threats to this fauna. Habitat alteration is a pervasive threat that has been magnified by market forces and globalization (e.g. extensive agricultural development in Amazonia), and threatens increasing numbers of populations and species. Climate change poses even greater threats, from changes in rainfall and runoff regimes and resulting changes in vegetative structure and composition to secondary influences on fire dynamics. It is likely that many changes have yet to be recognized, but existing threats suggest that the future may bring dramatic changes in the distribution of many mammal taxa, although it is not clear if key habitat elements (vegetation) will respond as rapidly as climatic factors, leading to substantial uncertainty. Climate change is likely to result in 'winners' and 'losers' but available information precludes detailed assessment of which species are likely to fall into which category. In the absence of long-term monitoring and applied research to characterize these threats more accurately, and to develop strategies to reduce their impacts, managers already are being faced with daunting challenges. As the line between 'pure' and 'applied' research blurs in the face of converging interests of scientists and society we hope that solutions to these critical issues will be incorporated in addressing anticipated conservation crises.

Patton, J. L., U. F. J. Pardinas, and G. D’Elia (eds.). 2015. Mammals of South America, Vol. 2. Rodents. University of Chicago Press, Chicago, Illinois, xxvi + 1336 pp. ISBN 978-0-226-16957-6, price (hard cover), $95. The second volume of Mammals of South America (MSA2) lives up to the hopes built up over 3 decades of anticipation. The 1st volume (MSA1—Gardner 2007) established a high bar for excellence (Kelt 2009; Voss 2009); Patton et al. and their able army of authors have met that with a groundbreaking synthesis of all things Rodentia on the Green Continent. This book is comprehensive, sweeping in scope and depth, and eminently readable. It provides the first such treatise on rodents of any such area with such detail. Whatever facet of mammal biology you study, if it involves South American rodents this book has information of relevance to your research. When I reviewed MSA1 (Kelt 2009) I noted that “If [this] is any indication of what’s coming, then . . . South American mammals are finally getting the synthesis they deserve.” MSA2 makes it clear that all hopes are more than met! I cannot wait for MSA3. MSA2 is structurally similar to MSA1. Following 26 pages of introductory materials, the taxonomic accounts comprise 1,048 pages with impressively few typographic errors. This is followed by 159 pages of Literature Cited, a 67-page Gazetteer, a 9-page list of taxa (627 species in 143 genera), 4 pages to list the 56 contributors (from 11 countries), and a 46-page Index. Reflecting the remarkable growth in Latin American mammalogy in recent years, 41 authors hail from either Mexico ( n = 2) or from 8 South American countries. Keys (mostly dichotomous) are provided for all genera and most species. For all genera, the authors provide General Comments (often including highly readable distillations of otherwise complex taxonomic histories), a Synonymy, Remarks, and a Key to Species, followed by presentation of all species in alphabetical order (in some cases, such as Proechimys , where species groups are … Department of Department of Wildlife, Fish, & Conservation Biology, University of California, Davis, CA 95616, USA; e-mail: dakelt{at}ucdavis.edu.

Forests in the Sierra Nevada, similar to those across the continent, have been substantially altered by logging, fire exclusion, and other human activities. Current forest management emphasizes maintenance or restoration of resiliency in the face of contemporary disturbance factors that include wildfire, climate change, continued urbanization, and invasive species. We evaluated responses of small mammals to forest management by monitoring a series of 12 replicate trapping grids in compositionally homogeneous forest over 8 years, and implemented 2 levels of canopy thinning. Livetrapping efforts (119,712 trap-nights) yielded 15,613 captures of 2,305 individuals of 13 species, and although forest structure was significantly influenced by canopy treatments, small mammal numbers and assemblage composition were not. To better understand this we assessed habitat associations of small mammals at 599 census points on 75 transects established in a stratified random manner throughout Plumas National Forest....

Continued range expansion of introduced eastern fox squirrels (Sciurus niger) in the western United States could lead to widespread damage to agricultural crops, facility infrastructures, and displacement of the native western gray squirrel (S. griseus). Because traditional management alternatives may not be feasible in many areas, public interest in the use of immunocontraceptive to control local populations has increased. We evaluated the efficacy of GonaCon™ immunocontraceptive vaccine for controlling eastern fox squirrel reproduction in Davis, California. We administered GonaCon to 33 male and 26 female fox squirrels, and a control substance to 33 males and 24 females. We subsequently compared the reproductive status, health, and serum concentrations of testosterone and progesterone of our treated and control populations. In our treated population, we also measured serum concentrations of antibodies to gonadotropin-releasing hormone (GnRH). To determine potential side effects of the vaccine, we recorded body weight and body condition of all animals, examined injection sites during each recapture, and observed the treated squirrels in the field for signs of discomfort and impaired mobility. Over 17 months, none of the recaptured GonaCon-treated females (n = 20) reproduced, compared to 12 of 15 control females. Treated males and females developed sufficient antibodies to GnRH to suppress reproduction, suggesting that GonaCon has the potential to be 100% effective in inhibiting reproduction in both sexes. We also observed a reduction in physical signs of reproductive activity for males (P

We studied the association between space sharing and kinship in a solitary rodent, the dusky-footed woodrat (Neotoma fuscipes). Genetic relatedness was inversely correlated with geographic distance for female woodrats but not for males, a pattern consistent with female philopatry and male dispersal. However, some female neighbors were unrelated, suggesting the possibility of female dispersal. Relatedness of female dyads was positively correlated with overlap of their home ranges and core areas, indicating that females were more likely to share space with relatives, whereas males showed no correlation between relatedness and the sharing of either home ranges or core areas. However, some females that shared space were not close relatives, and some closely related males shared space. House sharing was exhibited both by close relatives and by distantly related or unrelated woodrats, and was not correlated with relatedness. The kin structuring we describe likely resulted from a pattern of female philopatry and male dispersal, but also may have resulted from kin-directed behaviors by females.

The species composition of the Chilean avifauna is well-defined taxonomically but is not well known ecologically. We sampled avian communities at a biosphere reserve in coastal north-central Chile in three seasons over six years (18 surveys total) and characterized them in terms of community structure and composition. The avifauna (S = 56 species) was dominated by insectivores (S = 20), carnivores (S = 14), and granivores (S = 13), with lesser contributions by omnivores (S = 5), nectarivores (S = 2), folivores (S = 1), and one vagrant piscivore. The fauna varied greatly between summer and winter, and in most years the breeding season also was distinct. Eighteen species constituted a core group of residents observed in nearly all surveys, but at least 15 species were nomadic or migratory. Our site supported more insectivorous species in winter but more granivores and omnivores in the breeding season, although this observation may be confounded by species' detectability. The structure of the set o...

Rooted in the conceptual revolutions of the 1960s and 1970s, contemporary research on the ecology of desert small mammals has progressed markedly in recent decades. Areas of particular emphasis include the role of extrinsic (e.g., climate) compared with intrinsic (e.g., density-dependence) factors on population growth and associated metrics, the role of competition compared with predation in influencing foraging decisions and habitat selection, the influence of small mammals on community structure and composition via consumption and redistribution of plant materials, and as ecological engineers and keystone species (or guilds). Recent emphasis on the energetic basis of assemblage composition is intriguing and warrants further work, and the generality of zero-sum dynamics requires further assessment. Desert systems continue to be the focus of much ecological research, and small mammals remain central figures in understanding the interplay between biotic and abiotic factors and between intrinsic and extrinsic drivers. Small mammals in deserts worldwide exemplify the importance of diverse approaches to ecological research, including local manipulative field experiments, long-term demographic monitoring, and both laboratory and field-based studies on behavioral and foraging ecology.

We determined home-range overlap among northern flying squirrels (Glaucomys sabrinus) to assess their spatial organization. We found extensive home-range overlap among females, and though this overlap could reflect social behavior, we found no evidence of attraction among females, with only one instance of den sharing. Instead, our results suggest that females share foraging areas but may be territorial in portions of the home range, especially around den trees and during young-rearing. Home-range overlap could also result from, the extrinsic effect of forest fragmentation due to timber harvest, which might impede dispersal and force squirrels to cluster on remaining fragments of suitable habitat.

The abundance of exotic plants is thought to be limited by competition with resident species (including plants and generalist herbivores). In contrast, observations in semiarid Chile suggest that a native generalist rodent, the degu (Octodon degus), may be facilitating the expansion of exotic annual plants. We tested this hypothesis with a 20-year data set from a World Biosphere Reserve in mediterranean Chile. In this semiarid environment, rainfall varies annually and dramatically influences cover by both native and exotic annual plants; degu population density affects the composition and cover of exotic and native annual plants. In low-rainfall years, cover of both native and exotic herbs is extremely low. Higher levels of precipitation result in proportional increases in cover of all annual plants (exotic and native species), leading in turn to increases in degu population densities, at which point they impact native herbs in proportion to their greater cover, indirectly favoring the expansion of exotic plants. We propose that bottom-up control of consumers at our site results in top-down indirect facilitation of invasive annual herbs, and that this pattern may be general to other semiarid ecosystems.

The spotted owl ( Strix occidentalis ) is a late-successional forest dependent species that is sensitive to forest management practices throughout its range. An increase in the frequency and spatial extent of stand-replacing fires in western North America has prompted concern for the persistence of spotted owls and other sensitive late-successional forest associated species. However, there is sparse information on the effects of fire on spotted owls to guide conservation policies. In 2004–2005, we surveyed for California spotted owls during the breeding season at 32 random sites (16 burned, 16 unburned) throughout late-successional montane forest in Yosemite National Park, California. Our burned areas burned at all severities, but predominately involved low to moderate fire severity. Based on an information theoretic approach, spotted owl detection and occupancy rates were similar between burned and unburned sites. Nest and roost site occupancy was best explained by a model that combined total tree basal area (positive effect) with cover by coarse woody debris (negative effect). The density estimates of California spotted owl pairs were similar in burned and unburned forests, and the overall mean density estimate for Yosemite was higher than previously reported for montane forests. Our results indicate that low to moderate severity fires, historically common within montane forests of the Sierra Nevada, California, maintain habitat characteristics essential for spotted owl site occupancy. These results suggest that managed fires that emulate the historic fire regime of these forests may maintain spotted owl habitat and protect this species from the effects of future catastrophic fires.

The golden-mantled ground squirrel (Callospermophilus lateralis) is considered an asocial species, characterized by agonistic interactions, nonsharing of territories and early dispersal. The species is poorly studied, so we used radiotelemetry to determine home range size, home range overlap and dispersal. Home ranges of 12 adult females averaged 3.75 ha (range = 1.14–13.52) using the 95% fixed kernel method. Home ranges overlapped substantially but core areas did not, indicating territoriality may be expressed over only a portion of the home range, and an index of dynamic interaction was neutral, indicating neither attraction nor avoidance between females. Most (80%) of 20 juveniles dispersed during their first summer, but some delayed dispersal until at least their yearling summer. Our results provide support for the classification of golden-mantled ground squirrels as asocial but suggest that the expression of territoriality and early dispersal may be variable.

The American Society of Mammalogists herein provides revised guidelines for personnel working with rodents potentially infected with viruses that cause hantavirus pulmonary syndrome (HPS) in humans. We also clarify that previously published guidelines, including those of the United States Centers for Disease Control and Prevention (CDC), were not intended to apply to field-workers conducting nonviral-based research on rodents. Unfortunately, institutional animal care and use committees and other safety officers have assumed that current CDC recommendations are requirements for conducting safe field research. They then have misapplied the original CDC recommendations to field researchers conducting behavioral, ecological, taxonomic, and other research, making field research increasingly and unnecessarily difficult. Herein, we provide guidelines that have been modified from those published by the CDC to incorporate new information about HPS risk and to better match the level of personal protection to the level of risk associated with a wider array of field activities.

The introduction of lake trout ( Salvelinus namaycush ) to Yellowstone Lake in Yellowstone National Park has contributed to a significant decline in the endangered Yellowstone cutthroat trout ( Oncorhynchus clarki bouvieri ), leading to concern over the persistence of this subspecies but also to piscivorous predators in this community. We assessed the impact of lake trout on a key piscivore, the river otter ( Lontra canadensis ) in two lakes in Yellowstone National Park. Yellowstone Lake continues to support a native cutthroat trout population, although the recent introduction of lake trout has dramatically impacted the cutthroat trout population. Nearby Lewis Lake has an entirely introduced fish fauna of lake trout, brown trout ( Salmo trutta ), and Utah chub ( Gilia atraria ) but lacks cutthroat trout. Analysis of otter scat from Yellowstone Lake implicated trout (lake or cutthroat trout) as a major prey item (57% of scat), whereas stable isotopes identified longnose suckers ( Catostomus catostomus ) as the primary prey there (58% of diet). By contrast, scat from Lewis Lake implicated minnows, presumably Utah chub, as the primary prey for otters occupying that lake (86%), while stable isotopes implicated brown trout (64%) over both lake trout and Utah chub (36% combined). Our data establish the importance of alternative prey to otters and suggest that lake trout-induced reductions in cutthroat trout may not be catastrophic for otter populations here. These data do not necessarily exonerate lake trout, as their impact on other species, most notably grizzly bears ( Ursus arctos ) and piscivorous birds, has been documented to be substantial, and further data on the nutritional value of alternate prey are required to confirm or refute a working hypothesis that otter populations will continue to thrive in the face of the lake trout invasion.

The riparian brush rabbit (Sylvilagus bachmani riparius) is an endangered species found in dense, brushy habitat in the California’s Central Valley. We implemented a reintroduction program to bolster populations at a Federal Wildlife Refuge and to assess factors influencing mortality and subsequent survival of released individuals. Between July 2002 and July 2005, we reintroduced 325 captive-bred individuals to unoccupied habitat within their historic range using a soft-release strategy and monitored their subsequent survival with radiotelemetry. Longer time in soft-release pens resulted in increased monthly survival. Rabbits were most susceptible to post-release mortality during the first 4 weeks following reintroduction and both body mass and length of time in the soft-release enclosure influenced this relationship. When we controlled for release mortality during this acclimation period, subsequent monthly survival probabilities were most strongly influenced by release year (year 1 vs. years 2 and 3) and by a catastrophic flooding event; length of time in the soft-release enclosure remained an important variable in longer-term survival. Cause of mortality was unknown for the majority of deaths (61.9%), but predation (including presumptive predation) was the greatest known cause of death in translocated rabbits (26.4%). Reintroduction programs should employ an adaptive management approach with ongoing monitoring of target animals and concurrent analysis to allow managers to adjust methods as conditions dictate.