Informing wetland management with waterfowl movement and sanctuary use responses to human-induced disturbance.

Long-term environmental management to prevent waterfowl population declines is informed by ecology, movement behavior and habitat use patterns. Extrinsic factors, such as human-induced disturbance, can cause behavioral changes which may influence movement and resource needs, driving variation that affects management efficacy. To better understand the relationship between human-based disturbance and animal movement and habitat use, and their potential effects on management, we GPS tracked 15 dabbling ducks in California over ~4-weeks before, during and after the start of a recreational hunting season in October/November 2018. We recorded locations at 2-min intervals across three separate 24-h tracking phases: Phase 1) two weeks before the start of the hunting season (control (undisturbed) movement); Phase 2) the hunting season opening weekend; and Phase 3) a hunting weekend two weeks after opening weekend. We used GLMM models to analyze variation in movement and habitat use under hunting pressure compared with 'normal' observed patterns prior to commencement of hunting. We also compared responses to differing levels of disturbance related to the time of day (high - shooting/~daytime); moderate - non-lethal (~crepuscular); and low - night). During opening weekend flight (% time and distance) more than doubled during moderate and low disturbance and increased by ~50% during high disturbance compared with the pre-season weekend. Sanctuary use tripled during moderate and low disturbance and increased ~50% during high disturbance. Two weeks later flight decreased in all disturbance levels but was only less than the pre-season levels during high disturbance. In contrast, sanctuary use only decreased at night, although not to pre-season levels, while daytime doubled from ~45% to >80%. Birds adjust rapidly to disturbance and our results have implications for energetics models that estimate population food requirements. Management would benefit from reassessing the juxtaposition of essential sanctuary and feeding habitats to optimize wetland management for waterfowl.

Niches of three sympatric montane ground-dwelling squirrels: Relative importance of climate, topography, and landcover.

Species with different ecological niches will likely exhibit distinct responses to a changing environment. Differences in the magnitude of niche specialization may also indicate which species may be more vulnerable to environmental change, as many life-history characteristics are known to affect climate change vulnerability. We characterized the niche space of three sympatric high-elevation ground-dwelling squirrels, yellow-bellied marmot (Marmota flaviventer), Belding's ground squirrel (Urocitellus beldingi), and golden-mantled ground squirrel (Callospermophilus lateralis), in the alpine and upper subalpine regions of the Sierra Nevada in California. We used 5879 observations of individual squirrels, collected from 4 years (2009-2012) of transect survey data, to quantify which ecogeographical variable types (climate, topography, or landcover) were most important in defining the niche of each species. We conducted Ecological Niche Factor Analysis to quantify the niche and generate indices of "marginality" (magnitude of selection) and "specialization" (narrowness of niche space). All three species demonstrated differential use of niche space when compared to the available niche space. Moreover, the relative importance of the variables shaping the niche differed among these species. For example, the presence of meadows was important in defining the niche for U. beldingi and M. flaviventer, but the presence of conifers was important to C. lateralis. Precipitation was important in defining the niche for all three species, positively so for U. beldingi, and negatively for the other two species. The niche breadth of these three species was also positively associated with geographic range size. Mammals in high-elevation mountain systems often are perceived as vulnerable to climate shifts, but our results underscore the importance of also including non-climate-based factors in defining the niche. The overall magnitude of niche selection for all three species was driven by a combination of topographic, climatic, and landcover factors; thus, efforts to forecast areas where these species can persist in the future need to evaluate from more than just a climatic perspective.

Assessing small-mammal trapping design using spatially explicit capture recapture (SECR) modeling on long-term monitoring data.

Few studies have evaluated the optimal sampling design for tracking small mammal population trends, especially for rare or difficult to detect species. Spatially explicit capture-recapture (SECR) models present an advancement over non-spatial models by accounting for individual movement when estimating density. The salt marsh harvest mouse (SMHM; Reithrodontomys raviventris) is a federal and California state listed endangered species endemic to the San Francisco Bay-Delta estuary, California, USA; where a population in a subembayment has been continually monitored over an 18-year period using mark-recapture methods. We analyzed capture data within a SECR modeling framework that allowed us to account for differences in detection and movement between sexes. We compared the full dataset to subsampling scenarios to evaluate how the grid size (area) of the trap design, trap density (spacing), and number of consecutive trapping occasions (duration) influenced density estimates. To validate the subsampling methods, we ran Monte Carlo simulations based on the true parameter estimates for each specific year. We found that reducing the area of the trapping design by more than 36% resulted in the inability of the SECR model to replicate density estimates within the SE of the original density estimates. However, when trapping occasions were reduced from 4 to 3-nights the density estimates were indistinguishable from the full dataset. Furthermore, reducing trap density by 50% also resulted in density estimates comparable to the full dataset and was a substantially better model than reducing the trap area by 50%. Overall, our results indicated that moderate reductions in the number of trapping occasions or trap density could yield similar density estimates when using a SECR approach. This approach allows the optimization of field trapping efforts and designs by reducing field efforts while maintaining the same population estimate compared to the full dataset. Using a SECR approach may help other wildlife programs identify sampling efficiencies without sacrificing data integrity for long term monitoring of population densities.

Effects of invasive plants on fire regimes and postfire vegetation diversity in an arid ecosystem.

We assessed the impacts of co-occurring invasive plant species on fire regimes and postfire native communities in the Mojave Desert, western USA. We analyzed the distribution and co-occurrence patterns of three invasive annual grasses (Bromus rubens, Bromus tectorum, and Schismus spp.) known to alter fuel conditions and community structure, and an invasive forb (Erodium cicutarium) which dominates postfire sites. We developed species distribution models (SDMs) for each of the four taxa and analyzed field plot data to assess the relationship between invasives and fire frequency, years postfire, and the impacts on postfire native herbaceous diversity. Most of the Mojave Desert is highly suitable for at least one of the four invasive species, and 76% of the ecoregion is predicted to have high or very high suitability for the joint occurrence of B. rubens and B. tectorum and 42% high or very high suitability for the joint occurrence of the two Bromus species and E. cicutarium. Analysis of cover from plot data indicated two or more of the species occurred in 77% of the plots, with their cover doubling with each additional species. We found invasive cover in burned plots increased for the first 20 years postfire and recorded two to five times more cover in burned than unburned plots. Analysis also indicated that native species diversity and evenness as negatively associated with higher levels of relative cover of the four invasive taxa. Our findings revealed overlapping distributions of the four invasives; a strong relationship between the invasives and fire frequency; and significant negative impacts of invasives on native herbaceous diversity in the Mojave. This suggests predicting the distributions of co-occurring invasive species, especially transformer species, will provide a better understanding of where native-dominated communities are most vulnerable to transformations following fire or other disturbances.

The role of physical activity and feeding schedule on the kinetics of inhaled and oral toluene in rats.

Published studies of the kinetics of toluene in rats have shown that its concentration in the blood rises during inhalation and falls after exposure stops; a similar uptake profile and longer persistence in blood typify the kinetics after oral exposure. Because rats in these studies are typically inactive during exposure, and behavioral tests of the acute effects of toluene require physical activity and altered feeding schedules, this study examined the role of physical activity and feeding status on the uptake of toluene given by the two routes. Two groups of adult male Long-Evans rats were conditioned to eat in the lab during the day. A group of "conditioned-active" (C-A) rats performed a lever-pressing task (LPT) for 1 h, either while inhaling toluene vapor (2000 ppm) or after a gavage dose (800 mg/kg toluene in corn oil). Another group of "conditioned-sedentary" (C-S) rats was dosed similarly but did not perform the LPT. A third group of "home cage" (HC) rats was not conditioned to eat during the day, but was maintained under typical laboratory conditions (eating at night in the home cage) before receiving toluene by gavage. In the conditioned rats, physical activity during inhalation exposure increased the concentrations of toluene in blood (from 35.8 +/- 2.5 to 45.2 +/- 3.2 mg/L after 60 min) and brain (from 73.4 +/- 5.3 to 103.0 +/- 3.8 mg/L after 60 min), but did not affect those concentrations after oral toluene. The time course of the uptake of toluene into blood and brain of HC rats followed that of published data. In contrast, toluene concentrations in the blood and brain of orally dosed conditioned rats fell rapidly compared to HC rats and published data (at 60 min after dosing, blood concentrations were: C-S rats, 17.2 +/- 1.7 mg/L; HC rats, 69.4 +/- 9.6 mg/L; and brain concentrations were: C-S rats, 30.9 +/- 5.0 mg/L; HC rats, 96.6 +/- 18.5 mg/L). These studies demonstrate the importance of physical activity for the uptake of inhaled toluene, and the importance of feeding conditions for the elimination of oral toluene.

Pathogen infection and exposure, and ectoparasites of the federally endangered Amargosa vole (Microtus californicus scirpensis), California, USA.

Abstract We surveyed pathogens and ectoparasites among federally endangered Amargosa voles (Microtus californicus scirpensis) and sympatric rodents in Tecopa Hot Springs, Inyo County, California, December 2011-November 2012. We aimed to assess disease and detect possible spillover from or connectivity with other hosts within and outside the Amargosa ecosystem. We assessed 71 individual voles and 38 individual sympatric rodents for current infection with seven vector-borne zoonotic pathogens and past exposure to five pathogens. Thirteen percent of Amargosa voles were PCR positive for Toxoplasma gondii, a zoonotic protozoan that may alter host behavior or cause mortality. Additionally, we found antibodies against Borrelia burgdorferi sensu lato (SL) spp. in 21% of voles, against Anaplasma phagocytophilum in 2.6%, Rickettsia spp. in 13%, relapsing fever Borrelia (3.9%), and T. gondii (7.9%). Sympatric rodents also had active infections with Borrelia SL spp. (15%). Of the ectoparasites collected, the tick Ixodes minor is of particular interest because the study area is well outside of the species' reported range and because I. minor ticks infest migratory birds as well as rodents, showing a potential mechanism for pathogens to be imported from outside the Amargosa ecosystem.

Ultra-low-stress thin-film interference filters.

A method to reduce the optical degrading effect of coating stress in a thin-film filter by releasing the filter from the substrate on which it was deposited is described. An extremely challenging 8-skip-0 100 GHz wavelength-division-multiplexing band-splitting filter is demonstrated.

Mechanical characteristics of optical coatings prepared by various techniques: a comparative study.

Good performance of optical coatings depends on the appropriate combination of optical and mechanical properties. Therefore, successful applications require good understanding of the relationship between optical microstructural and mechanical characteristics and film stability. In addition, there is a lack of standard mechanical tests that allow one to compare film properties measured in different laboratories. We give an overview of the methodology of mechanical measurements suitable for optical coatings; this includes depth-sensing indentation, scratch resistance, friction, abrasion and wear testing, and stress and adhesion evaluation. We used the techniques mentioned above in the same laboratory to systematically compare the mechanical behavior of frequently used high- and low-index materials, namely, TiO2, Ta2O5, and SiO2, prepared by different complementary techniques. They include ion-beam-assisted deposition by electron-beam evaporation, magnetron sputtering, dual-ion-beam sputtering, plasma-enhanced chemical-vapor deposition, and filtered cathodic arc deposition. The mechanical properties are correlated with the film microstructure that is inherently related to energetic conditions during film growth.