Search

A fundamental question about the ecology of herbivore populations pertains to the relative influence of biotic and abiotic processes on nutritional condition. Nutritional condition is influenced in important, yet poorly understood, ways by plant secondary metabolites (PSMs) which can adversely affect a herbivore's physiology and energetics. Here we assess the relative influence of various abiotic (weather) and biotic (intraspecific competition, predation risk and diet composition) factors on indicators of nutritional condition and the energetic costs of detoxifying PSMs for the moose population in Isle Royale National Park (USA). Specifically, we observed interannual variation in the ratio of urea nitrogen to creatinine (UN:C), an indicator of nutritional restriction, over 29 years and the ratio of glucuronic acid to creatinine (GA:C), an indicator of energetic investment in detoxifying PSMs, over 19‐years. Both UN:C and GA:C were measured in samples of urine‐soaked snow. Most importantly, climatic factors explained 66% of the interannual variation in UN:C, with moose being more nutritionally stressed during winters with deep snow and during winters that followed warm summers. None of the biotic factors (density, predation, diet composition) were useful predictors of UN:C or GA:C. The absence of a relationship between diet composition and either UN:C or GA:C suggests that the nutritional ecology of wild herbivores is probably complicated by fine‐scale variation in protein content and concentrations of PSMs amongst plants of the same species. UN:C increased with GA:C at both the individual and population‐level. That result is consistent with detoxification being energetically costly, such that it impairs nutritional condition and also highlights how spatio‐temporal variation in the intake and detoxification of PSMs may influence population dynamics. Lastly, because we observed interannual variation in nutritional condition over three decades and detoxification over two decades these findings are relevant to concerns about how herbivore populations respond to climate change. [ABSTRACT FROM AUTHOR]

Heterogeneous vegetation structure can create a variable landscape of predation risk—a fearscape—that influences the use and selection of habitat by animals. Mapping the functional properties of vegetation that influence predation risk (e.g., concealment and visibility) across landscapes can be challenging. Traditional ground-based measures of predation risk are location specific and limited in spatial resolution. We demonstrate the benefits of terrestrial laser scanning (TLS) to map the properties of vegetation structure that shape fearscapes. We used TLS data to estimate the concealment of prey from multiple vantage points, representing predator sightlines, as well as the visibility of potential predators from the locations of prey. TLS provides a comprehensive data set that allows an exploration of how habitat changes may affect prey and predators. Together with other remotely sensed imagery, TLS could facilitate the scaling up of fearscape analyses to promote the management and restoration of landscapes. [ABSTRACT FROM PUBLISHER]

Understanding dietary specialization in herbivores has theoretical and practical implications in ecology, yet defining niche breadth consistently has been problematic. To increase clarity and communication among ecologists and among disciplines (i.e., chemists, pharmacologists), we propose a specialization key for mammalian herbivores that assigns "obligatory" and "facultative" modifiers to the terms "specialist" and "generalist". These modifiers are assigned based on (1) relative breadth of the animal's realized niche and diet (what it eats), (2) relative breadth of the fundamental niche and available diet (what it could eat), (3) the extent of chemical or physical characteristics, termed "difficulty", that make food items either low in value or unpalatable to most herbivores, and (4) relevant temporal and spatial scales at which diets and niche breadth were measured. Obligatory specialists always have a narrow realized niche consisting of difficult food items, and morphological adaptations and/or the loss of redundant behavioral flexibility that effectively limit their fundamental niches, precluding them from expanding their diet under changed environmental conditions. Facultative specialists have a consistently narrow realized niche for difficult foods during at least one spatial or temporal scale, but have a broad enough fundamental niche to allow them to expand their diet to include less difficult foods when environmental conditions allow. Facultative generalists have the broadest fundamental niche, allowing them to consume a wide variety of foods. However, they may occasionally demonstrate a narrow realized niche, focused on less difficult plants than is the case with specialists. Finally, the obligatory generalists always have a wide realized niche because of a relatively narrow fundamental niche, precluding them from eating much of any difficult plant. We summarize hypothesized characteristics of mammalian herbivores in each of the four categories of specialization. We demonstrate the need for further work on defining the realized and fundamental niches, comparing among herbivores across categories conducted under similar conditions, and understanding the nature of trade-offs required for specialization and generalization for both community and phylogenetically based analyses. \ [ABSTRACT FROM AUTHOR]

A central goal in understanding the ecology and evolution of animals is to identify factors that constrain or expand breadth of diet. Selection of diet in many animals is often constrained by chemical deterrents (i.e., secondary metabolites) in available food items. The integration of chemistry and ecology has led to a significant understanding of the chemical complexity of prey (e.g., animals, plants, and algae) and the resultant foraging behavior of consumers. However, most of the literature on chemical defenses of marine and terrestrial prey lacks a mechanistic understanding of how consumers tolerate, or avoid, chemically-defended foods. In order to understand ecological patterns of foraging and co-evolutionary relationships between prey and consumers, we must advance our understanding of the physiological mechanisms responsible for chemical interactions. Such mechanistic studies require the integration of the discipline of pharmacology with ecology, which we call "PharmEcology." Pharmacology provides the tools and insight to investigate the fate (what the body does to a chemical) and action (what a chemical does to the body) of chemicals in living organisms, whereas ecology provides the insight into the interactions between organisms (e.g., herbivores) and their environment (e.g., plants). Although, the general concepts of pharmacology were introduced to ecologists studying plant-herbivore interactions over 30 years ago, the empirical use of pharmacology to understand mechanisms of chemical interactions has remained limited. Moreover, many of the recent biochemical, molecular and technical advances in pharmacology have yet to be utilized by ecologists. The PharmEcology symposium held at a meeting of the Society for Integrative and Comparative Biology in January of 2009 was developed to define novel research directions at the interface of pharmacology and ecology. [ABSTRACT FROM AUTHOR]

We propose that the exploitation of the bioactive properties of secondary metabolites (SMs) by animals can provide a "treatment" against various challenges that perturb homeostasis in animals. The unified theoretical framework for the exploitation of SMs by animals is based on a synthesis of research from a wide range of fields and although it is focused on providing generalized predictions for herbivores that exploit SMs of plants, predictions can be applied to understand the exploitation of SMs by many animals. In this review, we argue that the probability of SM exploitation is determined by the relative difference between the cost of a homeostatic challenge and the toxicity of the SM and we provide various predictions that can be made when considering behavior under a homeostatic perspective. The notion that animals experience and respond to costly challenges by exploiting therapeutic SMs provides a relatively novel perspective to explain foraging behavior in herbivores, specifically, and behavior of animals in general. We provide evidence that animals can exploit the biological activity of SMs to mitigate the costs of infection by parasites, enhance reproduction, moderate thermoregulation, avoid predation, and increase alertness. We stress that a better understanding of animal behavior requires that ecologists look beyond their biases that SMs elicit punishment and consider a broader view of avoidance or selection of SMs relative to the homeostatic state. Finally, we explain how understanding exploitation of SMs by animals could be applied to advance practices of animal management and lead to discovery of new drugs. [ABSTRACT FROM AUTHOR]

Host microbial communities (hereafter, the 'microbiome') are recognized as an important aspect of host health and are gaining attention as a useful biomarker to understand the ecology and demographics of wildlife populations. Several studies indicate that the microbiome may contribute to the adaptive capacity of animals to changing environments associated with increasing habitat fragmentation and rapid climate change. To this end, we investigated the gut microbiome of pronghorn (Antilocapra americana), an iconic species in an environment that is undergoing both climatic and anthropogenic change. The bacterial composition of the pronghorn gut microbiome has yet to be described in the literature, and thus our study provides important baseline information about this species. We used 16S rRNA amplicon sequencing of fecal samples to characterize the gut microbiome of pronghorn—a facultative sagebrush (Artemisia spp.) specialist in many regions where they occur in western North America. We collected fecal pellets from 159 captured female pronghorn from four herds in the Red Desert of Wyoming during winters of 2013 and 2014. We found small, but significant differences in diversity of the gut microbiome relative to study area, capture period, and body fat measurements. In addition, we found a difference in gut microbiome composition in pronghorn across two regions separated by Interstate 80. Results indicated that the fecal microbiome may be a potential biomarker for the spatial ecology of free-ranging ungulates. The core gut microbiome of these animals—including bacteria in the phyla Firmicutes (now Bacillota) and Bacteroidota—remained relatively stable across populations and biological metrics. These findings provide a baseline for the gut microbiome of pronghorn that could potentially be used as a target in monitoring health and population structure of pronghorn relative to habitat fragmentation, climate change, and management practices. [ABSTRACT FROM AUTHOR]

Large‐scale disturbances, such as megafires, motivate restoration at equally large extents. Measuring the survival and growth of individual plants plays a key role in current efforts to monitor restoration success. However, the scale of modern restoration (e.g., >10,000 ha) challenges measurements of demographic rates with field data. In this study, we demonstrate how unoccupied aerial system (UAS) flights can provide an efficient solution to the tradeoff of precision and spatial extent in detecting demographic rates from the air. We flew two, sequential UAS flights at two sagebrush (Artemisia tridentata) common gardens to measure the survival and growth of individual plants. The accuracy of Bayesian‐optimized segmentation of individual shrub canopies was high (73–95%, depending on the year and site), and remotely sensed survival estimates were within 10% of ground‐truthed survival censuses. Stand age structure affected remotely sensed estimates of growth; growth was overestimated relative to field‐based estimates by 57% in the first garden with older stands, but agreement was high in the second garden with younger stands. Further, younger stands (similar to those just after disturbance) with shorter, smaller plants were sometimes confused with other shrub species and bunchgrasses, demonstrating a need for integrating spectral classification approaches that are increasingly available on affordable UAS platforms. The older stand had several merged canopies, which led to an underestimation of abundance but did not bias remotely sensed survival estimates. Advances in segmentation and UAS structure from motion photogrammetry will enable demographic rate measurements at management‐relevant extents. [ABSTRACT FROM AUTHOR]

Sagebrush identification can be improved by using a relatively easy ultraviolet (UV) light test on specimens. Sagebrush produces a variety of water-soluble polyphenols called coumarins, which fluoresce a blue color under UV light and can help differentiate species, subspecies, and hybrids. We tested 16 different sagebrush taxa (including species and subspecies) from herbarium specimens and found 3 taxa (low sagebrush, Artemisia arbuscula; Wyoming sagebrush, A. tridentata wyomingensis; and basin sagebrush, A. t. tridentata) that were often misidentified. We show that the UV light test can greatly improve identification of these species. Moreover, given that the UV+ chemicals that discriminate taxa are also considered an indirect biomarker of sagebrush palatability for some herbivores, the UV light test can be used to predict forage quality for threatened species like sage-grouse (Centrocercus spp.) and pygmy rabbits (Brachylagus idahoensis). Collecting voucher specimens of sagebrush at wildlife study sites and comparing their UV intensity to historical herbarium specimens could help identify both current and changing availability of palatable sagebrush for wildlife. We found that even herbarium specimens >80 years old still fluoresce under UV light. [ABSTRACT FROM AUTHOR]

Sage-grouse are two closely related iconic species of the North American West, with historically broad distributions across sagebrush-steppe habitat. Both species are dietary specialists on sagebrush during winter, with presumed adaptations to tolerate the high concentrations of toxic secondary metabolites that function as plant chemical defenses. Marked range contraction and declining population sizes since European settlement have motivated efforts to identify distinct population genetic variation, particularly that which might be associated with local genetic adaptation and dietary specialization of sage-grouse. We assembled a reference genome and performed whole-genome sequencing across sage-grouse from six populations, encompassing both species and including several populations on the periphery of the species ranges. Population genomic analyses reaffirmed genome-wide differentiation between greater and Gunnison sage-grouse, revealed pronounced intraspecific population structure, and highlighted important differentiation of a small isolated population of greater sage-grouse in the northwest of the range. Patterns of genome-wide differentiation were largely consistent with a hypothesized role of genetic drift due to limited gene flow among populations. Inferred ancient population demography suggested persistent declines in effective population sizes that have likely contributed to differentiation within and among species. Several genomic regions with single-nucleotide polymorphisms exhibiting extreme population differentiation were associated with candidate genes linked to metabolism of xenobiotic compounds. In vitro activity of enzymes isolated from sage-grouse livers supported a role for these genes in detoxification of sagebrush, suggesting that the observed interpopulation variation may underlie important local dietary adaptations, warranting close consideration for conservation strategies that link sage-grouse to the chemistry of local sagebrush. [ABSTRACT FROM AUTHOR]

Field‐based transplant gardens, including common and reciprocal garden experiments, are a powerful tool for studying genetic variation and gene‐by‐environment interactions. These experiments assume that individuals within the garden represent independent replicates growing in a homogenous environment. Plant neighborhood interactions are pervasive across plant populations and could violate assumptions of transplant garden experiments. We demonstrate how spatially explicit models for plant–plant interactions can provide novel insights on genotypes' performance in field‐transplant garden designs. We used individual‐based models, based on data from a sagebrush (Artemisia spp.) common garden, to simulate the impact of spatial plant–plant interactions on between‐group differences in plant growth. We found that planting densities within the range of those used in many common gardens can bias experimental outcomes. Our results demonstrate that higher planting densities can lead to inflated group differences and may confound genotypes' competitive ability and genetically underpinned variation. Synthesis. We propose that spatially explicit models can help avoid biased results by informing the design and analysis of field‐based transplant garden experiments. Alternately, including neighborhood effects in post hoc analyses of transplant garden experiments is likely to provide novel insights into the roles of biotic factors and density dependence in genetic differentiation. [ABSTRACT FROM AUTHOR]

Increased ecological disturbances, species invasions, and climate change are creating severe conservation problems for several plant species that are widespread and foundational. Understanding the genetic diversity of these species and how it relates to adaptation to these stressors are necessary for guiding conservation and restoration efforts. This need is particularly acute for big sagebrush (Artemisia tridentata; Asteraceae), which was once the dominant shrub over 1,000,000 km2 in western North America but has since retracted by half and thus has become the target of one of the largest restoration seeding efforts globally. Here, we present the first reference-quality genome assembly for an ecologically important subspecies of big sagebrush (A. tridentata subsp. tridentata) based on short and long reads, as well as chromatin proximity ligation data analyzed using the HiRise pipeline. The final 4.2-Gb assembly consists of 5,492 scaffolds, with nine pseudochromosomal scaffolds (nine scaffolds comprising at least 90% of the assembled genome; n=9). The assembly contains an estimated 43,377 genes based on ab initio gene discovery and transcriptional data analyzed using the MAKER pipeline, with 91.37% of BUSCOs being completely assembled. The final assembly was highly repetitive, with repeat elements comprising 77.99% of the genome, making the Artemisia tridentata subsp. tridentata genome one of the most highly repetitive plant genomes to be sequenced and assembled. This genome assembly advances studies on plant adaptation to drought and heat stress and provides a valuable tool for future genomic research. [ABSTRACT FROM AUTHOR]

Plant communities are composed of complex phenotypes that not only differ among taxonomic groups and habitats but also change over time within a species. Restoration projects (e.g. translocations and reseeding) can introduce new functional variation in plants, which further diversifies phenotypes and complicates our ability to identify locally adaptive phenotypes for future restoration. Near‐infrared spectroscopy (NIRS) offers one approach to detect the chemical phenotypes that differentiate plant species, populations, and phenological states of individual plants over time. We use sagebrush (Artemisia spp.) as a case study to test the accuracy by which NIRS can classify variation within taxonomy and phenology of a plant that is extensively managed and restored. Our results demonstrated that NIRS can accurately classify species of sagebrush within a study site (75–96%), populations of sagebrush within a subspecies (99%), annual phenology within a population (>99%), and seasonal phenology within individual plants (>97%). Low classification accuracy by NIRS in some sites may reflect heterogeneity associated with natural hybridization, translocation of nonlocal seed sources from past restoration, or complex gene‐by‐environment interactions. Advances in our ability to detect and interpret spectral signals from plants may improve both the selection of seed sources for targeted conservation and the capacity to monitor long‐term changes in vegetation. [ABSTRACT FROM AUTHOR]

How intensely animals use habitat features depends on their functional properties (i.e., how the feature influences fitness) and the spatial and temporal scale considered. For herbivores, habitat use is expected to reflect the competing risks of starvation, predation, and thermal stress, but the relative influence of each functional property is expected to vary in space and time. We examined how a dietary and habitat specialist, the pygmy rabbit (Brachylagus idahoensis), used these functional properties of its sagebrush habitat—food quality, security, and thermal refuge—at two hierarchical spatial scales (microsite and patch) across two seasons (winter and summer). At the microsite and patch scales, we determined which plant functional traits predicted the number of bites (i.e., foraging) by pygmy rabbits and the number of their fecal pellets (i.e., general habitat use). Pygmy rabbits used microsites and patches more intensely that had higher crude protein and aerial concealment cover and were closer to burrows. Food quality was more influential when rabbits used microsites within patches. Security was more influential in winter than summer, and more at Cedar Gulch than Camas. However, the influence of functional properties depended on phytochemical and structural properties of sagebrush and was not spatiotemporally consistent. These results show function‐dependent habitat use that varied according to specific activities by a central‐place browsing herbivore. Making spatially explicit predictions of the relative value of habitat features that influence different types of habitat use (i.e., foraging, hiding, and thermoregulating) will improve how we predict patterns of habitat use by herbivores and how we monitor and manage functional traits within habitats for wildlife. [ABSTRACT FROM AUTHOR]

Congeneric species often share ecological niche space resulting in competitive interactions that either limit co-occurrence or lead to niche partitioning. Differences in fundamental nutritional niches mediated through character displacement or isolation during evolution are potential mechanisms that could explain overlapping distribution patterns of congenerics. We directly compared nutritional requirements and tolerances that influence the fundamental niche of mule (Odocoileus hemionus) and white-tailed deer (O. virginianus), which occur in allopatry and sympatry in similar realized ecological niches across their ranges in North America. Digestible energy and protein requirements and tolerances for plant fiber and plant secondary metabolites (PSMs) of both deer species were quantified using in vivo digestion and intake tolerance trials with six diets ranging in content of fiber, protein, and PSMs using tractable deer raised under identical conditions in captivity. We found that compared with white-tailed deer, mule deer required 54% less digestible protein and 21% less digestible energy intake per day to maintain body mass and nitrogen balance. In addition, they had higher fiber, energy, and dry matter digestibility and produced glucuronic acid (a byproduct of PSM detoxification) at a slower rate when consuming the monoterpene α-pinene. The mule deers' enhanced physiological abilities to cope with low-quality, chemically defended forages relative to white-tailed deer might minimize potential competitive interactions in shared landscapes and provide a modest advantage to mule deer in habitats dominated by low-quality forages. [ABSTRACT FROM AUTHOR]

Herbivores that forage on chemically defended plants consume complex mixtures of plant secondary metabolites (PSMs). However, the mechanisms by which herbivores tolerate mixtures of PSMs are relatively poorly understood. As such, it remains difficult to predict how PSMs, singly or as complex mixtures, influence diet selection by herbivores. Although relative rates of detoxification of PSMs have been used to explain tolerance of PSMs by dietary specialist herbivores, few studies have used the rate of detoxification of individual PSMs to understand dietary preferences of individual herbivores for individual versus mixtures of PSMs. We coupled in vivo experiments using captive feeding trials with in vitro experiments using enzymatic detoxification assays to evaluate the dietary preferences and detoxification capacities of pygmy rabbits (Brachylagus idahoensis), dietary specialists on sagebrush (Artemisia spp.), and mountain cottontails (Sylvilagus nuttallii), dietary generalists. We compared preference for five single PSMs in sagebrush compared to a mixture containing those same five PSMs. We hypothesized that relative preference for individual PSMs would coincide with faster detoxification capacity for those PSMs by specialists and generalists. Pygmy rabbits generally showed little preference among individual PSMs compared to mixed PSMs, whereas mountain cottontails exhibited stronger preferences. Pygmy rabbits had faster detoxification capacities for all PSMs and consumed higher concentrations of individual PSMs versus a mixture than cottontails. However, detoxification capacity for an individual PSM did not generally coincide with preferences or avoidance of individual PSMs by either species. Cottontails avoided, but pygmy rabbits preferred, camphor, the PSM with the slowest detoxification rate by both species. Both species avoided β-pinene despite it having one of the fastest detoxification rate. Taken together our in vivo and in vitro results add to existing evidence that detoxification capacity is higher in dietary specialist than generalist herbivores. However, results also suggest that alternative mechanisms such as absorption and the pharmacological action of individual or mixtures of PSMs may play a role in determining preference of PSMs within herbivore species. [ABSTRACT FROM AUTHOR]

Both temperature and diet quality play an important role in the time and energy budgets of small mammalian herbivores. However, little is known about how temperature and diet quality interact to influence diet selection, nutrient extraction, and energetics, and how these effects might differ among species. Therefore, we examined the effects of diet quality and temperature on aspects of the foraging ecology of two species of lagomorphs, pygmy rabbits ( Brachylagus idahoensis ), which are small dietary specialists, and mountain cottontail rabbits ( Sylvilagus nuttallii ), which are larger dietary and habitat generalists. In a series of feeding experiments, we investigated 1) the effects of temperature on selection of plant fiber and the plant secondary metabolite 1,8 cineole in their diets, 2) effects of temperature and plant fiber on daily intake, digestion, and passage of food, 3) effects of plant fiber and 1,8 cineole on resting metabolic rate, and 4) how these interactions differ between the rabbit species. Both species chose to eat more total food and a greater proportion of high fiber food that passed more quickly through the digestive system in colder temperatures. However, temperature did not affect how much 1,8 cineole the rabbits consumed nor how thoroughly they digested food. Food quality affected how well they digested the dry matter in the food, but not their resting metabolic rate. Understanding how the interactions between ambient temperature and food quality affect selection of diets and intake by small mammalian herbivores, and the physiological mechanisms governing these choices, is useful for predicting how these species might respond to changes in both temperature and food quality and inform conservation and restoration strategies. [ABSTRACT FROM AUTHOR]

Understanding behavioral responses of animals to the thermal environment is of increasing importance under changing climate regimes. Thermoregulatory behaviors, such as exploitation of thermal refugia or temporal partitioning of activity, can buffer organisms against hot and cold thermal extremes but may conflict with other life history needs. Our objective was to evaluate strategies for behavioral thermoregulation by a small-bodied endotherm to test hypotheses about tradeoffs between thermal and security needs across seasons. We quantified the influence of both thermal and security properties of habitat on selection of rest sites by pygmy rabbits (Brachylagus idahoensis), and we identified environmental and endogenous factors affecting levels of activity during summer and winter. Behavioral strategies varied seasonally in response to both thermal challenges and risk of predation. During summer, rabbits selected rest sites with high concealment and low shortwave radiation, but activity levels were independent of ambient temperature. During winter, however, security, but not thermal properties, influenced selection of rest sites, and activity was positively correlated with ambient temperature during the most thermally stressful periods of the day (dawn, dusk, and night). The types of nuanced behavioral plasticity that we documented in response to the thermal environment is likely to be overlooked in evaluations of species tolerance to changing climates. Understanding the potential for behavior to buffer individuals as well as the limits of behavior to shield populations from consequences of climate change is critical for effective conservation of vulnerable species. [ABSTRACT FROM AUTHOR]

GPS telemetry markedly enhances the temporal and spatial resolution of animal location data, and recent advances in micro-GPS receivers permit their deployment on small mammals. One such technological advance, snapshot technology, allows for improved battery life by reducing the time to first fix via postponing recovery of satellite ephemeris (satellite location) data and processing of locations. However, no previous work has employed snapshot technology for small, terrestrial mammals. We evaluated performance of two types of micro-GPS (< 20 g) receivers (traditional and snapshot) on a small, semi-fossorial lagomorph, the pygmy rabbit (Brachylagus idahoensis), to understand how GPS errors might influence fine-scale assessments of space use and habitat selection. During stationary tests, microtopography (i.e., burrows) and satellite geometry had the largest influence on GPS fix success rate (FSR) and location error (LE). There was no difference between FSR while animals wore the GPS collars above ground (determined via light sensors) and FSR generated during stationary, above-ground trials, suggesting that animal behavior other than burrowing did not markedly influence micro-GPS errors. In our study, traditional micro-GPS receivers demonstrated similar FSR and LE to snapshot receivers, however, snapshot receivers operated inconsistently due to battery and software failures. In contrast, the initial traditional receivers deployed on animals experienced some breakages, but a modified collar design consistently functioned as expected. If such problems were resolved, snapshot technology could reduce the tradeoff between fix interval and battery life that occurs with traditional micro-GPS receivers. Our results suggest that micro-GPS receivers are capable of addressing questions about space use and resource selection by small mammals, but that additional techniques might be needed to identify use of habitat structures (e.g., burrows, tree cavities, rock crevices) that could affect micro-GPS performance and bias study results. [ABSTRACT FROM AUTHOR]

Radio‐transmitters are used widely in wildlife research because they allow researchers to track individual animals and monitor their activity. However, to provide unbiased information about a population, transmitters must be deployed on a representative sample of animals and must not alter the behavior of the individuals. The greater sage‐grouse Centrocercus urophasianus has been studied intensively using radio‐transmitters for the last several decades. A previous study demonstrated that males fitted with necklace‐style radio‐transmitters could be less likely to attend breeding grounds than those without transmitters. However, how transmitters affect the behavior of males that do attend leks has not been investigated. Therefore, we investigated whether radio‐transmitters alter the characteristics of strut vocalizations or display frequency of male sage‐grouse. We measured time and frequency characteristics of vocalizations from six collared and seven non‐collared adult male sage‐grouse on three leks in south‐central Idaho, and for two collared and four non‐collared males from two leks in northern Nevada. Only one vocalization characteristic (maximum frequency of the primary whistle) differed between collared and non‐collared males across both populations. Collared males showed a lower maximum frequency of the primary whistle that typically fell outside the range of variation for non‐collared males. This was the only difference found in the sample from Nevada, while in Idaho, collared males also exhibited a narrower bandwidth for the primary whistle (lower maximum frequency and higher minimum frequency), a shorter primary whistle, and a shorter secondary coo than non‐collared males. Some acoustic characteristics of sage‐grouse strut vocalizations are linked to mate choice by females, and therefore our results suggest that collars could reduce male mating success by altering the production of breeding vocalizations. Therefore, we recommend using alternative attachment techniques for behavioral studies of male sage‐grouse. [ABSTRACT FROM AUTHOR]

Triclocarban (TCC) and triclosan (TCS), two of the most commonly used antimicrobial compounds, can be introduced into ecosystems by applying wastewater treatment plant biosolids to agricultural fields. Concentrations of TCC and TCS were measured in different trophic levels within a terrestrial food web encompassing land-applied biosolids, soil, earthworms (Lumbricus), deer mice (Peromyscus maniculatus), and eggs of European starlings (Sturnus vulgaris) and American kestrels (Falco sparverius) at an experimental site amended with biosolids for the previous 7 years. The samples from this site were compared to the same types of samples from a reference (biosolids-free) agricultural site. Inter-site comparisons showed that concentrations of both antimicrobials were higher on the experimental site in the soil, earthworms, mice (livers), and European starling eggs, but not American kestrel eggs, compared to the control site. Inter-species comparisons on the experimental site indicated significantly higher TCC concentrations in mice (TCC: 12.6-33.3 ng/g) and in starling eggs (TCC: 15.4-31.4 ng/g) than in kestrel eggs (TCC: 3.6 ng/g). Nesting success of kestrels only was significantly lower on the experimental site compared to the reference site due to nest abandonment. This study demonstrates that biosolids-derived TCC and TCS are present throughout the terrestrial food web, including secondary (e.g., starlings) and tertiary (i.e., kestrels) consumers, after repeated, long-term biosolids application. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Self-medication in Animals," by J. C. de Roode et al. the April 12, 2013 issue, which includes a reply from the authors.

Small herbivores face risks of predation while foraging and are often forced to trade off food quality for safety. Life history, behaviour, and habitat of predator and prey can influence these trade-offs. We compared how two sympatric rabbits (pygmy rabbit, Brachylagus idahoensis; mountain cottontail, Sylvilagus nuttallii) that differ in size, use of burrows, and habitat specialization in the sagebrush-steppe of western North America respond to amount and orientation of concealment cover and proximity to burrow refuges when selecting food patches. We predicted that both rabbit species would prefer food patches that offered greater concealment and food patches that were closer to burrow refuges. However, because pygmy rabbits are small, obligate burrowers that are restricted to sagebrush habitats, we predicted that they would show stronger preferences for greater cover, orientation of concealment, and patches closer to burrow refuges. We offered two food patches to individuals of each species during three experiments that either varied in the amount of concealment cover, orientation of concealment cover, or distance from a burrow refuge. Both species preferred food patches that offered greater concealment, but pygmy rabbits generally preferred terrestrial and mountain cottontails preferred aerial concealment. Only pygmy rabbits preferred food patches closer to their burrow refuge. Different responses to concealment and proximity to burrow refuges by the two species likely reflect differences in perceived predation risks. Because terrestrial predators are able to dig for prey in burrows, animals like pygmy rabbits that rely on burrow refuges might select food patches based more on terrestrial concealment. In contrast, larger habitat generalists that do not rely on burrow refuges, like mountain cottontails, might trade off terrestrial concealment for visibility to detect approaching terrestrial predators. This study suggests that body size and evolutionary adaptations for using habitat, even in closely related species, might influence anti-predator behaviors in prey species. [ABSTRACT FROM AUTHOR]

Animal habitat selection is a process that functions at multiple, hierarchically structured spatial scales. Thus multi-scale analyses should be the basis for inferences about factors driving the habitat selection process. Vertebrate herbivores forage selectively on the basis of phytochemistry, but few studies have investigated the influence of selective foraging (i.e., fine-scale habitat selection) on habitat selection at larger scales. We tested the hypothesis that phytochemistry is integral to the habitat selection process for vertebrate herbivores. We predicted that habitats selected at three spatial scales would be characterized by higher nutrient concentrations and lower concentrations of plant secondary metabolites (PSMs) than unused habitats. We used the Greater Sage-Grouse (Centrocercus urophasianus), an avian herbivore with a seasonally specialized diet of sagebrush, to test our hypothesis. Sage-Grouse selected a habitat type (black sagebrush, Artemisia nova) with lower PSM concentrations than the alternative (Wyoming big sagebrush, A. tridentata wyomingensis). Within black sagebrush habitat, Sage-Grouse selected patches and individual plants within those patches that were higher in nutrient concentrations and lower in PSM concentrations than those not used. Our results provide the first evidence for multi-scale habitat selection by an avian herbivore on the basis of phytochemistry, and they suggest that phytochemistry may be a fundamental driver of habitat selection for vertebrate herbivores. [ABSTRACT FROM AUTHOR]