Stable isotope analysis of diet confirms niche separation of two sympatric species of Namib Desert lizard

We used stable isotopes of carbon and nitrogen to study the trophic niche of two species of insectivorous lizards, the Husab sand lizard Pedioplanis husabensis and Bradfield's Namib day gecko living sympatrically in the Namib Desert. We measured the δ¹³C and δ¹⁵N ratios in lizard blood tissues with different turnover times (whole blood, red blood cells and plasma) to investigate lizard diet in different seasons. We also measured the δ¹³C and δ¹⁵N ratios in available arthropod prey and plant tissues on the site, to identify the avenues of nutrient movement between lizards and their prey. Through the use of stable isotope mixing models, we found that the two lizard species relied on a largely non‐overlapping but seasonally variable array of arthropods: P. husabensis primarily fed on termites, beetles and wasps, while R. bradfieldi fed mainly on ants, wasps and hemipterans. Nutrients originating from C₃ plants were proportionally higher for R. bradfieldi than for P. husabensis during autumn and late autumn/early winter, although not summer. Contrary to the few available data estimating the trophic transfer of nutrients in ectotherms in mixed C₃ and C₄/crassulacean acid metabolism (CAM) plant landscapes, we found that our lizard species primarily acquired nutrients that originated from C₄/CAM plants. This work adds an important dimension to the general lack of studies using stable isotope analyses to estimate lizard niche partitioning and resource use.     

Carnivore stable carbon isotope niches reflect predator–prey size relationships in African savannas

Predator–prey size relationships are among the most important patterns underlying the structure and function of ecological communities. Indeed, these relationships have already been shown to be important for understanding patterns of macroevolution and differential extinction in the terrestrial vertebrate fossil record. Stable isotope analysis (SIA) is a powerful remote approach to examining animal diets and paleodiets. The approach is based on the principle that isotope compositions of consumer tissues reflect those of their prey. In systems where resource isotope compositions are distributed along a body size gradient, SIA could be used to reconstruct predator–prey size relationships. We analyzed stable carbon isotope distributions amongst mammalian herbivores in extant and Plio–Pleistocene African savanna assemblages, and show that the range of δ¹³C values among mammalian prey species (herbivores and rodents) increases with body mass (BM), because C₄ plant feeding (essentially grazing) is more common among larger taxa. Consequently, δ¹³C values of mammalian carnivores in these systems are related to species' BM, reflecting a higher average C₄ prey component in the diets of larger‐bodied carnivores. This pattern likely emerges because only the largest carnivores in these systems have regular access to the C₄ prey base, whereas smaller carnivores do not. The δ¹³C–BM relationship observed in mammalian carnivores is a potentially powerful approach for reconstructing and parameterizing predator–prey size relationships in contemporary and fossil savanna assemblages, and for interpreting how various behavioral, ecological and environmental factors influence prey size selection.     

Grazing-Exclusion Effects on Aboveground Biomass and Water-Use Efficiency of Alpine Grasslands on the Northern Tibetan Plateau

The influences of grazing exclusion on plant species composition and intrinsic water-use efficiency (W_i) of alpine grasslands on the Northern Tibet Plateau are not well understood. We conducted a multisite transect field survey across the three main alpine ecosystems (meadow, steppe, and desert steppe) with nine pairs of grazing-excluded and adjacent open grazed pastures. Short-term grazing exclusion (started in 2006) did not result in significant changes in nutrients or bulk density of the surface soils (0–15 cm), but it slightly changed the aboveground biomass (AGB) and coverage at both community and species levels. Community foliar δ¹³C and W_i differed among alpine grassland types, with values for steppe being similar to those for meadow and with desert steppe values being higher than both of these. Foliar δ¹³C and inferred W_i differed among the dominant species and varied negatively with precipitation and positively with temperature in 2010. These results confirm that there is an environmentally selective effect on the replacement of dominant species. There was no evident difference in foliar δ¹³C or W_i between grazing-excluded and open grazed sites, but there was a slight increase of AGB and coverage in grazing-excluded sites compared to open grazed ones at the species and community levels. These results indicated that grazing exclusion may have no clear influence on the physiological processes related to foliar water usage at the species level, but may have a cumulative effect on the carbon–water balance at the community level. Slight changes in linear regressions of foliar δ¹³C and W_i plotted across climatic gradients indicated that grasslands under grazing management might be more sensitive to regional climatic changes.     

Distinctive diet‐tissue isotopic discrimination factors derived from the exclusive bamboo‐eating giant panda

Stable isotope analysis is very useful in animal ecology, especially in diet reconstruction and trophic studies. Differences in isotope ratios between consumers and their diet, termed discrimination factors, are essential for studies of stable isotope ecology and are species‐specific and tissue‐specific. Given the specialized bamboo diet and clear foraging behavior, here, we calculated discrimination factors for carbon and nitrogen isotopes from diet to tissues (tooth enamel, hair keratin and bone collagen) for the giant panda (Ailuropoda melanoleuca), a species derived from meat‐eating ancestors. Our results showed that carbon discrimination factor obtained from giant panda tooth enamel (ε ¹³C_{diet‐enamel} = 10.0‰) and nitrogen discrimination factors from hair keratin (Δ¹⁵N_diet‐hair = 2.2‰) and bone collagen (Δ¹⁵N_{diet‐collagen} = 2.3‰) were lower, and carbon discrimination factors from hair keratin (Δ¹³C_diet‐hair = 5.0‰) and bone collagen (Δ¹³C_{diet‐collagen} = 6.1‰) were higher than those of other mammalian carnivores, omnivores and herbivores. Such distinctive values are likely the result of a low‐nutrient and specialized bamboo diet, carnivore‐like digestive system and exceptionally low metabolism in giant pandas.     

Habitat restoration is the greatest challenge for population recovery of Hainan gibbons (Nomascus hainanus)

Hainan gibbons are among the world's most critically endangered primates, with a remaining population of only 35 individuals distributed across 5 social groups in the Bawangling Branch of the Hainan Tropical Rainforest National Park, China. Habitat conversion and forest fragmentation over the past 40 years have reduced their geographical distribution by 95%. In the absence of a quantitative assessment of the availability of remaining suitable habitat, it is unclear whether this species can survive to the end of this century. We used behavioral observations, ArcGIS, remote sensing, stereo optical imagery, and MaxEnt modeling to identify patterns of Hainan gibbon range use and compare changes in the distribution of suitable forest types and areas of forest fragmentation over the past 20 years (2000–2020). The results indicate that the combined range of the 5 extant Hainan gibbon groups totaled 14.89 km². The home range of the smallest group (Group E, 3 individuals) was 1.51 km², which likely represents the minimum home range size for this species. The remaining area of highly suitable and moderately suitable habitat totals 26.9 km². However, habitat connectivity across the gibbon range is very low (less than 0.5), limiting the ability of Hainan gibbons to move between forest patches. The results of this study indicate that the availability of suitable habitat in Bawangling is insufficient to allow for future Hainan gibbon population growth. Therefore, immediate action must be taken to restore, reforest, and establish ecological corridors to reconnect areas of suitable habitat for these critically endangered gibbons.     

Epidemiological Survey of Equine Pythiosis in the Brazilian Pantanal and Nearby Areas: Results of 76 Cases

A clinical epidemiological study was conducted among 34 rural properties located within the Brazilian Pantanal region and nearby areas between 2007 and 2010. The diagnosis of equine pythiosis was based on antibody detection (by enzyme-linked immunosorbent assay), polymerase chain reaction, histopathological analysis, and cultures positive for Pythium insidiosum. The majority of the affected animals (85%) were in the Pantanal biome, which had a higher disease prevalence (0.9%-66.7%) than that of the Cerrado (2.7%-33.3%). The disease was more prevalent in the rainy season (January-March), with an abrupt fall in the number of cases during the drought period (April–September; correlation of R² = 0.77; P < .01). Generally, the average prevalence of equine pythiosis in both regions was 5%, with mortality and lethality rates of 1.3% and 23.1%, respectively, in the Pantanal and 2.3% and 45.5%, respectively, in the Cerrado. However, the treatment with immunotherapy may have underestimated these numbers, especially in the Pantanal. Animals older than 1 year were 8.09 times more affected by the disease than younger animals in the same environment (P < .05). A correlation between the anatomical area of the lesion and the type of skin color was also observed. Approximately 73% of the lesions were found in dark-pigmented areas, and animals with a dark coat color were affected more frequently. These findings highlight the importance of hematophagous insects in the epidemiology of pythiosis because these areas are preferred for blood feeding.     

Fire History in a Chaparral Ecosystem: Implications for Conservation of a Native Ungulate

Mature chaparral vegetation in the San Gabriel Mountains, California, resulting from long fire-return intervals (50–70 yr), has resulted in reduced visibility and availability and quality of forage, all of which are important attributes of mountain sheep (Ovis canadensis) habitat. Concomitantly, vegetation changes have decreased availability and quality of forage. We developed a resource-selection model to determine the effect of fire history on habitat use by mountain sheep, examined the hypotheses that habitat selection was associated with fire occurrence, and determined whether fire occurrence influenced the amount of potential habitat available to mountain sheep. The best model indicated that mountain sheep selected vegetation that had burned within 15 yr and avoided areas that had not burned within that time frame. We then used our model to quantify potential changes in mountain sheep habitat that have occurred over time based on fire conditions. We identified 390 km² of mountain sheep habitat that existed in 2002 (when only 63 mountain sheep were tallied), 486 km² in 1980 (when the mountain sheep population was at its highest), and 422 km² in 2004 (just after a series of large wildfires). We also estimated that 615 km² of suitable habitat would be available in a hypothetical situation in which the entire study area burned. Our results suggest that restoration of mountain sheep to their historical distribution in chaparral ecosystems will depend upon more frequent fires in areas formerly occupied by those specialized herbivores.     

Density and carrying capacity in the forgotten tigerland: Tigers in the understudied Nepalese Churia

While there are numerous wildlife ecology studies in lowland areas of Nepal, there are no in‐depth studies of the hilly Churia habitat even though it comprises 7642 km² of potential wildlife habitat across the Terai Arc. We investigated tiger, leopard and prey densities across this understudied habitat. Our camera trapping survey covered 536 km² of Churia and surrounding areas within Chitwan National Park (CNP). We used 161 trapping locations and accumulated 2097 trap‐nights in a 60‐day survey period during the winter season of 2010–2011. In addition, we walked 136 km over 81 different line transects using distance sampling to estimate prey density. We photographed 31 individual tigers, 28 individual leopards and 25 other mammalian species. Spatial capture–recapture methods resulted in lower density estimates for tigers, ranging from 2.3 to 2.9 tigers per 100 km², than for leopards, which ranged from 3.3 to 5.1 leopards per 100 km². In addition, leopard densities were higher in the core of the Churia compared to surrounding areas. We estimated 62.7 prey animals per 100 km² with forest ungulate prey (sambar, chital, barking deer and wild pig), accounting for 47% of the total. Based on prey availability, Churia habitat within CNP could potentially support 5.86 tigers per 100 km² but our density estimates were lower, perhaps indicating that the tiger population is below carrying capacity. Our results demonstrate that Churia habitat should not be ignored in conservation initiatives, but rather management efforts should focus on reducing human disturbance to support higher predator numbers.     

Additional considerations to the use of single‐step genomic predictions in a dominance setting

Recent publications indicate that single‐step models are suitable to estimate breeding values, dominance deviations and total genetic values with acceptable quality. Additive single‐step methods implicitly extend known number of allele information from genotyped to non‐genotyped animals. This theory is well derived in an additive setting. It was recently shown, at least empirically, that this basic strategy can be extended to dominance with reasonable prediction quality. Our study addressed two additional issues. It illustrated the theoretical basis for extension and validated genomic predictions to dominance based on single‐step genomic best linear unbiased prediction theory. This development was then extended to include inbreeding into dominance relationships, which is a currently not yet solved issue. Different parametrizations of dominance relationship matrices were proposed. Five dominance single‐step inverse matrices were tested and described as C¹ , C² , C³ , C⁴ and C⁵ . Genotypes were simulated for a real pig population (n = 11,943 animals). In order to avoid any confounding issues with additive effects, pseudo‐records including only dominance deviations and residuals were simulated. SNP effects of heterozygous genotypes were summed up to generate true dominance deviations. We added random noise to those values and used them as phenotypes. Accuracy was defined as correlation between true and predicted dominance deviations. We conducted five replicates and estimated accuracies in three sets: between all ( S₁ ), non‐genotyped ( S₂ ) and inbred non‐genotyped ( S₃ ) animals. Potential bias was assessed by regressing true dominance deviations on predicted values. Matrices accounting for inbreeding ( C³ , C⁴ and C⁵ ) best fit. Accuracies were on average 0.77, 0.40 and 0.46 in S₁ , S₂ and S₃ , respectively. In addition, C³ , C⁴ and C⁵ scenarios have shown better accuracies than C¹ and C² , and dominance deviations were less biased. Better matrix compatibility (accuracy and bias) was observed by re‐scaling diagonal elements to 1 minus the inbreeding coefficient ( C⁵ ).     

Soil Resources Influence Vegetation and Response to Fire and Fire-Surrogate Treatments in Sagebrush-Steppe Ecosystems

Current paradigm suggests that spatial and temporal competition for resources limit an exotic invader, cheatgrass (Bromus tectorum L.), which once established, alters fire regimes and can result in annual grass dominance in sagebrush steppe. Prescribed fire and fire surrogate treatments (mowing, tebuthiuron, and imazapic) are used to reduce woody fuels and increase resistance to exotic annuals, but may alter resource availability and inadvertently favor invasive species. We used four study sites within the Sagebrush Steppe Treatment Evaluation Project (SageSTEP) to evaluate 1) how vegetation and soil resources were affected by treatment, and 2) how soil resources influenced native herbaceous perennial and exotic annual grass cover before and following treatment. Treatments increased resin exchangeable NH₄⁺, NO₃^-, H₂PO₄^-, and K⁺, with the largest increases caused by prescribed fire and prolonged by application of imazapic. Burning with imazapic application also increased the number of wet growing degree days. Tebuthiuron and imazapic reduced exotic annual grass cover, but imazapic also reduced herbaceous perennial cover when used with prescribed fire. Native perennial herbaceous species cover was higher where mean annual precipitation and soil water resources were relatively high. Exotic annual grass cover was higher where resin exchangeable H₂PO₄^- was high and gaps between perennial plants were large. Prescribed fire, mowing, and tebuthiuron were successful at increasing perennial herbaceous cover, but the results were often ephemeral and inconsistent among sites. Locations with sandy soil, low mean annual precipitation, or low soil water holding capacity were more likely to experience increased exotic annual grass cover after treatment, and treatments that result in slow release of resources are needed on these sites. This is one of few studies that correlate abiotic variables to native and exotic species cover across a broad geographic setting, and that demonstrates how soil resources potentially influence the outcome of management treatments.     

Rapid Succession of Orthopteran Assemblages Driven by Patch Size and Connectivity

Bearing in mind the current dramatic decline in biodiversity, in addition to preserving remaining natural habitat patches, performing successful habitat restorations and land-use is increasingly essential. In this study, the effect of patch size and connectivity on the early succession of orthopteran assemblages was examined in reconstructed Central European sand habitats. The first comprehensive study on this topic demonstrated that the diversity of the assemblages in mid-successional stages (4^th and 5^th years of research) reached the value which characterised the control areas. Grazing can preserve habitats in this successional stage. Based on the results of the study in sand habitats belonging to low-productivity dry grasslands, to maintain heterogeneous habitat structures, traditional moderate grazing is recommended. Grazing by sheep is the most beneficial for maintaining the presence of open surfaces, closed patches, and fallen foliage cover in optimal proportions for orthopterans. It was also revealed, that during habitat restorations of sand grasslands, patch size and connectivity affect the species richness of habitat specialist orthopteran species strongly.     

Differences in Net Primary Productivity Among Contrasting Habitats in Artemisia ordosica Rangeland of Northern China

Artemisiaordosica Krasch. is a semishrub native to the Ordos Plateau of Inner Mongolia, northern China, and forms a unique and dominant vegetation type in the sandland of the region. To determine the variation of productivity in A. ordosica rangeland, we investigated net primary production (NPP), fine root turnover, soil microbial C (C_mic), and soil organic carbon density (SOC_d) on sand dunes differing in mobility (i.e., fixed, semifixed, and shifting sand dunes) in Mu Us sandland. We found that, on an area basis, the NPP, SOC_d, C_mic, and fine root turnover rates all increased with increasing vegetation cover. However, the ratios of root NPP to total NPP (RMR_N) increased with declining vegetation cover. Total NPP varied markedly among habitats and ranged from 18.3 g · m^-2 · yr^-1 for communities on the shifting sand dunes to 293.8 g · m^-2 · yr^-1 for communities on the fixed sand dunes; whereas the rates of fine root turnover varied from 0.16 · yr^-1 to 0.54 · yr^-1. Our study demonstrated that habitat change in sandland has significant impacts on ecosystem productivity by affecting many related aspects of NPP. From the perspective of biomass production, protection of the semifixed dunes from degradation should be taken as a higher priority than trying to convert shifting sand dunes to semifixed sand dunes; whereas conversion of semifixed sand dunes to fixed sand dunes would appear to be a much easier task than restoring shifting sand dunes.     

Impacts of Mesquite Distribution on Seasonal Space Use of Lesser Prairie-Chickens

Loss of native grasslands by anthropogenic disturbances has reduced availability and connectivity of habitat for many grassland species. A primary threat to contiguous grasslands is the encroachment of woody vegetation, which is spurred by disturbances that take on many forms from energy development, fire suppression, and grazing. These disturbances are exacerbated by natural- and human-driven cycles of changes in climate punctuated by drought and desertification conditions. Encroachment of honey mesquite (Prosopis glandulosa) into the prairies of southeastern New Mexico has potentially limited habitat for numerous grassland species, including lesser prairie-chickens (Tympanuchus pallidicinctus). To determine the magnitude of impacts of distribution of mesquite and how lesser prairie-chickens respond to mesquite presence on the landscape in southeastern New Mexico, we evaluated seasonal space use of lesser prairie-chickens in the breeding and nonbreeding seasons. We derived several remotely sensed spatial metrics to characterize the distribution of mesquite. We then used these data to create population-level resource utilization functions and predict intensity of use of lesser prairie-chickens across our study area. Home ranges were smaller in the breeding season compared with the nonbreeding season; however, habitat use was similar across seasons. During both seasons, lesser prairie-chickens used areas closer to leks and largely avoided areas with mesquite. Relative to the breeding season, during the nonbreeding season habitat use suggested a marginal increase in mesquite within areas of low intensity of use, yet aversion to mesquite was strong in areas of medium to high intensity of use. To our knowledge, our study is the first to demonstrate a negative behavioral response by lesser prairie-chickens to woody encroachment in native grasslands. To mitigate one of the possible limiting factors for lesser prairie-chickens, we suggest future conservation strategies be employed by land managers to reduce mesquite abundance in the southern portion of their current range.     

Ecosystem Water Use Efficiency in a Semiarid Shrubland and Grassland Community

Ecosystem water use efficiency (EWUE) is defined as the net carbon uptake per amount of water lost from the ecosystem and is a useful measure of the functionality in semiarid shrub and grassland communities. C₄ grasses have higher water use efficiency (WUE) than do C₃ shrubs, although it has been postulated that C₄ plants have lost much of their advantage due to the rising atmospheric CO₂ concentrations. The hypothesis was that C₄-grass-dominated ecosystems have a higher EWUE than C₃-shrub-dominated ecosystems under the present CO₂ concentration and climatic variability. Evapotranspiration (ET) and CO₂ fluxes were measured with Bowen ratio systems at a shrub and grass site for 6 years in southeastern Arizona. Two different methods were used to evaluate growing season EWUE using the ET and CO₂ fluxes. The first method estimated a net daytime growing season EWUE for the grass site at 1.74 g CO₂ · mm^-1 ET and 1.28 g CO₂ · mm^-1 ET at the shrub site. The second method estimated maximum EWUE during part of the growing season at 7.35 g CO₂ · mm^-1 ET for the grass site and 4.68 g CO₂ · mm^-1 ET for the shrub site, which was considered a significant difference at P = 0.056. Data variability of the first method precluded a statistical difference determination between sites, but the results indicated that the grass-dominated ecosystem was between 1.4 and 1.6 times more water use efficient than the shrub-dominated ecosystem. Mean annual growing season precipitation and ET were similar in the two ecosystems, but the higher EWUE of the grassland system enabled it to take up more carbon during the growing season than the shrub ecosystem. Ecosystem differences in CO₂ and H₂O flux have important management implications including primary productivity, C sequestration, and rangeland health.     

Optimizing the size of the area surveyed for monitoring a Eurasian lynx (Lynx lynx) population in the Swiss Alps by means of photographic capture–recapture

We studied the influence of surveyed area size on density estimates by means of camera‐trapping in a low‐density felid population (1–2 individuals/100 km²). We applied non‐spatial capture–recapture (CR) and spatial CR (SCR) models for Eurasian lynx during winter 2005/2006 in the northwestern Swiss Alps by sampling an area divided into 5 nested plots ranging from 65 to 760 km². CR model density estimates (95% CI) for models M₀ and M_h decreased from 2.61 (1.55–3.68) and 3.6 (1.62–5.57) independent lynx/100 km², respectively, in the smallest to 1.20 (1.04–1.35) and 1.26 (0.89–1.63) independent lynx/100 km², respectively, in the largest area surveyed. SCR model density estimates also decreased with increasing sampling area but not significantly. High individual range overlaps in relatively small areas (the edge effect) is the most plausible reason for this positive bias in the CR models. Our results confirm that SCR models are much more robust to changes in trap array size than CR models, thus avoiding overestimation of density in smaller areas. However, when a study is concerned with monitoring population changes, large spatial efforts (area surveyed ≥760 km²) are required to obtain reliable and precise density estimates with these population densities and recapture rates.     

Habitat use and home range of black-backed jackals (Canis mesomelas) on farmlands in the Midlands of KwaZulu-Natal,South Africa

Black-backed jackals (Canis mesomelas) are an abundant mesopredator on farmlands (croplands and rangelands) across South Africa. Given their adaptability in a changing anthropogenic landscape, knowledge of spatial movements can provide important ecological information on the species. We captured, collared and monitored five black-backed jackals in the Midlands of KwaZulu-Natal to determine their home range and habitat use in farmlands. The 95% fixed kernel (95% FK) home range sizes were large, showing a marked seasonal variation in movement. One adult male dispersed 150?km over two seasons (winter and spring) and thereafter settled into a home range that it maintained. Transient home ranges of males and juveniles were larger than resident home ranges. The mean resident home ranges (95% FK) across seasons for adult males, adult female and juvenile males were 11.4 ± 4.3 km², 5.6 ± 0.36?km² and 2.15 ± 0.45?km², respectively. The mean transient home ranges (95% FK) of all the seasons for adult and juvenile males were 1 181.93 ± 575.81 km² and 104.27 ± 35.64?km², respectively. Adult jackal preferred croplands in spring, summer and autumn but avoided croplands in winter. Variable habitat use and large home ranges in our study confirmed the species’ ability to adapt to agricultural areas.     

Using detection dogs and genetic analyses of scat to expand knowledge and assist felid conservation in Misiones,Argentina

Many carnivores require large ranges to meet their ecological and energetic needs; however, anthropogenic changes threaten species and their habitats. Camera traps have been used to effectively collect data on carnivores in a variety of habitat types; however, a single survey effort is typically limited to species that have similar body size, habitat use and movement patterns, and individual identification of animals is not always possible. We evaluated whether scat detection dogs could effectively survey for 4 wide‐ranging felids that vary in these characteristics: jaguars (Panthera onca), pumas (Puma concolor), ocelots (Leopardus pardalis) and oncillas (Leopardus tigrinus). From June to October 2009 and May to August 2011, a detection dog‐handler team detected 588 scats, from which 176 unique genotypes were detected. We assigned sex to 84.7% of the genotyped scats and identified 55 individuals multiple times. The effectiveness of these noninvasive techniques (detection dogs and genetic analyses of scat) not only opens the door for additional studies in areas that were previously difficult or impossible with standard survey techniques, but also provides conservationists with a set of tools that overcome some of the limitations associated with the use of camera traps alone.     

Northern Bobwhite (Colinus virginianus) Space Use Minimally Affected by Oil and Gas Development

Despite the fact that the northern bobwhite (Colinus virginianus Linnaeus; hereafter, bobwhite) is one of the most well-studied and widely distributed wildlife species in North America, we know little about how bobwhite respond to oil and gas infrastructure. We investigated the impacts of oil and gas development on space use of bobwhite using a multiseason approach. We captured and monitored bobwhite in the breeding season (1 April–30 September, n = 135 individuals) and nonbreeding season (1 October–31 March, n = 30 coveys) and modeled their habitat selection in a resource-utilization function (third order, within home range selection) and resource-selection function (second order, home range selection) format. Generally, energy infrastructure effects on bobwhite were neutral, but breeding season bobwhite did select for areas near low-traffic roads (β = ? 0.31 ± 0.15 SE). In the nonbreeding season, coveys selected for areas within their home range with a limited viewshed (i.e., areas with limited visibility of anthropogenic structures; β = ? 0.03 ± 0.02 SE). Selection differed between sexes for well pads (t = ? 2.12, P = 0.04) but was otherwise similar. At the level of home range selection, bobwhite exhibited a preference for areas with a low density of oil and gas wells and a high density of low-traffic roads during both the breeding and nonbreeding seasons (breeding: β_well = ? 0.14 ± 0.02, β_road = 0.26 ± 0.27; nonbreeding: β_well = ? 0.08 ± 0.03, β_road = 0.16 ± 0.03). As a generalist species, bobwhite appear to be largely tolerant of energy infrastructure and associated disturbances at moderate levels of development but may be sensitive to high densities of oil and gas pads.     

Fall Water Effects on Growing Season Soil Water Content and Plant Productivity

Understanding fall precipitation effects on rangelands could improve forage production forecasting and inform predictions of potential climate change effects. We used a rainout shelter and water addition to test effects of seasonal precipitation on soil water and annual net primary production of C₃ perennial grass, C₄ perennial grass, annual grasses, forbs, and all plants combined. Treatments were 1) drought during September−October and April−May (DD); 2) drought plus irrigation during September−October and drought during April−May (WD); 3) year-long ambient conditions (WW); and 4) ambient plus irrigation during September−October (W + W). Treatments created conditions ranking among the driest and wettest September−October periods since 1937. Fall water effects on soil water were not detectable by May at 15 cm and 30 cm. Effects persisted into July at 60 cm and 90 cm, depths below the primary root zone. With spring drought, annual net primary production was 344 kg ha⁻¹ greater when the previous fall was wet rather than dry. No differences were detected between fall water treatments when spring was wet and fall was about 184% (1 938 ± 117 kg ha⁻¹) or 391% of the median (1 903 ± 117 kg ha⁻¹). Fall water increased C₃ perennial grass when spring was also wet and had no effect under spring drought, when forage production concerns are greatest. Fall water did not affect C₄ perennial grass, and extremely wet fall conditions reduced forb production about 50%. The greatest effect of fall water was increased annual grass production. Even record high levels of fall water had minor effects on biomass, functional group composition, and soil water that were short-lived and overwhelmed by the influence of spring precipitation. Movement of fall water to deep soil by the growing season suggests plants that would most benefit from fall precipitation are those that could use it during fall (winter annuals), or deep-rooted species (shrubs).     

Validation of the n-alkane and NIRS techniques to estimate intake, digestibility and diet composition in sheep fed mixed lucerne: ryegrass diets

An experiment was carried out with sixteen non-pregnant, non-lactating adult Rasa Aragonesa ewes fed different proportions of lucerne and ryegrass hays to validate the use of n-alkanes and NIRS methods to estimate diet composition, intake and digestibility. The effect of two different faecal sampling procedures (daily pool (S1) or rectal spot samples (S2)) was also tested. The faecal concentration of n-alkanes was affected by the sampling procedure, although differences were lower than 12%. Faecal recoveries were not affected by diet, except in the case of C₂₃ (P < 0.0001), C₂₈ (P = 0.0264) and C₃₃ (P = 0.0241), and followed a curvilinear pattern with alkane chain length. Recovery was complete in the case of C₂₉, C₃₁ and C₃₃, which countersigns the usefulness of these internal markers for digestibility and digestive flow studies (especially C₃₁, given its high concentration in most plants). The faecal recoveries of C₃₁ and C₃₂ were not similar, the assumption of identity affecting in an important way the reliability of intake estimates. The NIRS methodology appeared as a promising alternative for predicting diet composition (R² of the cross-validation = 0.98) and faecal concentration of most natural alkanes, although that was not the case for dosed alkanes. In all cases, the prediction equations obtained from the spectra of the faecal spot samples were better than those obtained from daily pool samples.