Factors Affecting the Timing of Movements to Hibernation Sites by Western Toads (Anaxyrus boreas)

Herpetologica ◽  
2010 ◽  
Vol 66 (3) ◽  
pp. 250-258 ◽  
Author(s):  
Constance L. Browne ◽  
Cynthia A. Paszkowski
Keyword(s):  
Factors Affecting ◽  
Western Toads ◽  
Anaxyrus Boreas

Movement behaviour of adult western toads in a fragmented, forest landscape

2009 ◽  
Vol 87 (12) ◽  
pp. 1184-1194 ◽  
Author(s):  
Isabelle Deguise ◽  
John S. Richardson
Keyword(s):  
Forest Harvesting ◽  
Habitat Modification ◽  
Small Scale ◽  
Fragmented Landscape ◽  
Forest Patches ◽  
Movement Rates ◽  
Fragmented Forest ◽  
Fitness Consequences ◽  
Western Toads ◽  
Anaxyrus Boreas

Habitat loss and fragmentation are among the best documented explanations for the dramatic declines amphibians are experiencing globally. The western toad ( Anaxyrus boreas (Baird and Girard, 1852)) is an IUCN red-listed species whose distribution range has been significantly affected by habitat modification. We used radiotelemetry to follow daily, postbreeding movement patterns of 23 adult male toads in a fragmented landscape near Vancouver, British Columbia, Canada, composed of forest patches and small, recent clearcuts (~5 ha). Results showed that toads in forests oriented towards edges of clearcuts from at least as far as 150 m. Greater than 60% of toads released in forest patches chose to enter the clearcuts from adjacent forests, indicating high boundary permeability. Net displacement distance was not significantly reduced in these clearcuts; however, movement rates were significantly lower on clearcuts than in forest. This indicates that there is no structural impediment to movements; however, there still could be fitness consequences or an interaction with summer weather. Toads also used roads for their movement more frequently than at random relative to their area. These results suggest that the western toad’s movements may not be negatively affected by small-scale forest harvesting at our latitude during the spring.

scholarly journals The observed decline of Western Toads (Anaxyrus boreas) over several decades at a novel winter breeding site

2018 ◽  
Vol 132 (1) ◽  
pp. 53-57 ◽  
Author(s):  
Brian G. Slough ◽  
Alexander DeBruyn
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Cold Water ◽  
Breeding Site ◽  
Breeding Phenology ◽  
Warm Springs ◽  
Amphibian Chytrid Fungus ◽  
Western Toads ◽  
Anaxyrus Boreas ◽  
Extraordinary Feature ◽  
Winter Breeding

The Western Toad (Anaxyrus boreas) population of the Atlin Warm Springs in northwestern British Columbia has persisted since at least 1924. An extraordinary feature of the population has been winter breeding in late February to early March, while nearby cold-water populations breed in late-May. Metamorphosis of tadpoles, enhanced by the warm water, occurs as early as late-March. In 2008, Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) was documented in toadlets at the warm springs. Until 2005, as many as eight egg clutches and 25 breeding adults had been observed at the warm springs, after which the population declined. In 2017, novel spring breeding occurred in a cooler pond in the spring complex. Future observations will help determine whether the population is recovering and whether breeding phenology and habitat use have changed.

scholarly journals Shifts in temperature influence howBatrachochytrium dendrobatidisinfects amphibian larvae

2017 ◽  
Author(s):  
Paul W. Bradley ◽  
Michael D. Brawner ◽  
Thomas R. Raffel ◽  
Jason R. Rohr ◽  
Deanna H. Olson ◽  
...  
Keyword(s):  
Batrachochytrium Dendrobatidis ◽  
Temperature Shift ◽  
Amphibian Species ◽  
Change Models ◽  
Rana Aurora ◽  
Amphibian Larvae ◽  
Western Toads ◽  
Anaxyrus Boreas ◽  
Potential Shifts ◽  
Increased Susceptibility

AbstractMany climate change models predict increases in mean temperature, and increases in frequency and magnitude of temperature fluctuations. These potential shifts may impact ectotherms in several ways, including how they are affected by disease. Shifts in temperature may especially affect amphibians, a group with populations that have been challenged by several pathogens. Because amphibian hosts invest more in immunity at warmer than cooler temperatures and parasites may acclimate to temperature shifts faster than hosts (creating lags in optimal host immunity), researchers have hypothesized that a temperature shift from cold-to-warm might result in increased amphibian sensitivity to pathogens, whereas a shift from warm-to-cold might result in decreased sensitivity. Support for components of this climate-variability based hypothesis have been provided by prior studies of the fungusBatrachochytrium dendrobatidis(Bd) that causes the disease chytridiomycosis in amphibians. We experimentally tested whether temperature shifts before Bd exposure alter susceptibility to Bd in the larval stage of two amphibian species – western toads (Anaxyrus boreas) and northern red legged frogs (Rana aurora). Both host species harbored elevated Bd infection intensities under constant cold (15° C) temperature in comparison to constant warm (20° C) temperature. Additionally, both species experienced an increase in Bd infection abundance when shifted to 20° C from 15° C, compared to a constant 20° C but they experienced a decrease in Bd when shifted to 15° C from 20° C, compared to a constant 15° C. These results are in contrast to prior studies of adult amphibians that found increased susceptibility to Bd infection after a temperature shift in either direction, highlighting the potential for species and stage differences in the temperature-dependence of chytridiomycosis.

Progress In The Practical Application Of Automated Image Analysis To Tem Negatives

1977 ◽  
Vol 35 ◽  
pp. 214-217
Author(s):  
F. A. Heckman ◽  
E. Redman ◽  
J.E. Connolly
Keyword(s):  
Image Analysis ◽  
Image Quality ◽  
Exposure Time ◽  
Image Contrast ◽  
Automated Image Analysis ◽  
Practical Application ◽  
Factors Affecting ◽  
High Image Quality ◽  
Qualitative Evidence ◽  
Comprehensive Study

In our initial publication on this subject1) we reported results demonstrating that contrast is the most important factor in producing the high image quality required for reliable image analysis. We also listed the factors which enhance contrast in order of the experimentally determined magnitude of their effect. The two most powerful factors affecting image contrast attainable with sheet film are beam intensity and KV. At that time we had only qualitative evidence for the ranking of enhancing factors. Later we carried out the densitometric measurements which led to the results outlined below.Meaningful evaluations of the cause-effect relationships among the considerable number of variables in preparing EM negatives depend on doing things in a systematic way, varying only one parameter at a time. Unless otherwise noted, we adhered to the following procedure evolved during our comprehensive study:Philips EM-300; 30μ objective aperature; magnification 7000- 12000X, exposure time 1 second, anti-contamination device operating.

Factors affecting microstructural scale in liquid crystalline polymers

1990 ◽  
Vol 48 (4) ◽  
pp. 220-221
Author(s):  
Christine M. Dannels ◽  
Christopher Viney
Keyword(s):  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Factors Affecting ◽  
Crystalline Polymers ◽  
Thermal Expansion Coefficients ◽  
Low Thermal Expansion ◽  
Lower Viscosity ◽  
Fine Microstructure ◽  
Planar Orientation ◽  
Strength And Stiffness

Processing polymers from the liquid crystalline state offers several advantages compared to processing from conventional fluids. These include: better axial strength and stiffness in fibers, better planar orientation in films, lower viscosity during processing, low solidification shrinkage of injection moldings (thermotropic processing), and low thermal expansion coefficients. However, the compressive strength of the solid is disappointing. Previous efforts to improve this property have focussed on synthesizing stiffer molecules. The effect of microstructural scale has been overlooked, even though its relevance to the mechanical and physical properties of more traditional materials is well established. By analogy with the behavior of metals and ceramics, one would expect a fine microstructure (i..e. a high density of orientational defects) to be desirable.Also, because much microstructural detail in liquid crystalline polymers occurs on a scale close to the wavelength of light, light is scattered on passing through these materials.

Factors affecting dentist participation in a state Medicaid program

1990 ◽  
Vol 54 (11) ◽  
pp. 638-643 ◽  
Author(s):  
PC Damiano ◽  
ER Brown ◽  
JD Johnson ◽  
JP Scheetz
Keyword(s):  
Medicaid Program ◽  
Factors Affecting

Speech Therapy Services in a Large School System: A Six-Year Overview

1976 ◽  
Vol 7 (4) ◽  
pp. 207-219 ◽  
Author(s):  
Constance P. DesRoches
Keyword(s):  
School System ◽  
Speech Therapy ◽  
Factors Affecting ◽  
Case Load ◽  
Number Of Children ◽  
School Population ◽  
System A ◽  
Therapy Services ◽  
And Shifts ◽  
Selection Factors

A statistical review provides analysis of four years of speech therapy services of a suburban school system which can be used for comparison with other school system programs. Included are data on the percentages of the school population enrolled in therapy, the categories of disabilities and the number of children in each category, the sex and grade-level distribution of those in therapy, and shifts in case-load selection. Factors affecting changes in case-load profiles are identified and discussed.

Assessing the Link Between Perception and Production in Cantonese Tone Acquisition

2019 ◽  
Vol 62 (5) ◽  
pp. 1243-1257 ◽  
Author(s):  
Peggy Pik Ki Mok ◽  
Holly Sze Ho Fung ◽  
Vivian Guo Li
Keyword(s):  
Language Acquisition ◽  
General Principle ◽  
Choice Task ◽  
Factors Affecting ◽  
Tone Pair ◽  
Tone Production ◽  
Monosyllabic Words ◽  
Early Production ◽  
Forced Choice Task ◽  
Production Accuracy

Purpose Previous studies showed early production precedes late perception in Cantonese tone acquisition, contrary to the general principle that perception precedes production in child language. How tone production and perception are linked in 1st language acquisition remains largely unknown. Our study revisited the acquisition of tone in Cantonese-speaking children, exploring the possible link between production and perception in 1st language acquisition. Method One hundred eleven Cantonese-speaking children aged between 2;0 and 6;0 (years;months) and 10 adolescent reference speakers participated in tone production and perception experiments. Production materials with 30 monosyllabic words were transcribed in filtered and unfiltered conditions by 2 native judges. Perception accuracy was based on a 2-alternative forced-choice task with pictures covering all possible tone pair contrasts. Results Children's accuracy of production and perception of all the 6 Cantonese tones was still not adultlike by age 6;0. Both production and perception accuracies matured with age. A weak positive link was found between the 2 accuracies. Mother's native language contributed to children's production accuracy. Conclusions Our findings show that production and perception abilities are associated in tone acquisition. Further study is needed to explore factors affecting production accuracy in children. Supplemental Material https://doi.org/10.23641/asha.7960826

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