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E. Muths

Publications and source records attributed to E. Muths.

34 records · Page 2Linked to original sources
USGS2004

Sensitivity to acidification of subalpine ponds and lakes in north-western Colorado

Although acidifying deposition in western North America is lower than in many parts of the world, many high-elevation ecosystems there are extremely sensitive to acidification. Previous studies determined that the Mount Zirkel Wilderness Area (MZWA) has the most acidic snowpack and aquatic ecosystems that are among the most sensitive in the region. In this study, spatial and temporal variability of ponds and lakes in and near the MZWA were examined to determine their sensitivity to acidification and the effects of acidic deposition during and after snowmelt. Within the areas identified as sensitive to acidification based on bedrock types, there was substantial variability in acid-neutralizing capacity (ANC), which was related to differences in hydrological flowpaths that control delivery of weathering products to surface waters. Geological and topographic maps were of limited use in predicting acid sensitivity because their spatial resolution was not fine enough to capture the variability of these attributes for lakes and ponds with small catchment areas. Many of the lakes are sensitive to acidification (summer and autumn ANC < 100 µeq L −1 ), but none of them appeared to be threatened immediately by episodic or chronic acidification. In contrast, 22 ponds had minimum ANC < 30 µeq L −1 , indicating that they are extremely sensitive to acidic deposition and could be damaged by episodic acidification, although net acidity (ANC < 0) was not measured in any of the ponds during the study. The lowest measured pH value was 5·4, and pH generally remained less than 6·0 throughout early summer in the most sensitive ponds, indicating that biological effects of acidification are possible at levels of atmospheric deposition that occurred during the study. The aquatic chemistry of lakes was dominated by atmospheric deposition and biogeochemical processes in soils and shallow ground water, whereas the aquatic chemistry of ponds was also affected by organic acids and biogeochemical processes in the water column and at the sediment–water interface. These results indicate that conceptual and mechanistic acidification models that have been developed for lakes and streams may be inadequate for predicting acidification in less-understood systems such as ponds.

Hydrological Processes↗
USGS2003

Hatching success in salamanders and chorus frogs at two sites in Colorado, USA: Effects of acidic deposition and climate

The snowpack in the vicinity of the Mount Zirkel Wilderness Area is among the most acidic in the western United States. We analyzed water chemistry and examined hatching success in tiger salamanders and chorus frogs at ponds there and at nearby Rabbit Ears Pass (Dumont) to determine whether acid deposition affects amphibians or their breeding habitats at these potentially sensitive locations. We found a wide range of acid neutralizing capacity among ponds within sites; the minimum pH recorded during the experiment was 5.4 at one of 12 ponds with all others at pH ??? 5.7. At Dumont, hatching success for chorus frogs was greater in ponds with low acid neutralizing capacity; however, lowest pHs were >5.8. At current levels of acid deposition, weather and pond characteristics are likely more important than acidity in influencing hatching success in amphibian larvae at these sites.

Colorado↗
USGS2003

Home range and movements of boreal toads in undisturbed habitat

I sampled movements and amount of area used by boreal toads (Bufo boreas) between June and October for 3 yr. Females were found farther from the breeding site than were males, and mean home ranges, as calculated by the adaptive kernel method, were four times larger for females than for males. Temperature and snow accumulation were comparable over the study, but data collection was hampered by mortality of animals caused by an outbreak of amphibian chytridiomycosis in yr 2. These data provide insight into use of habitat by boreal toads in undisturbed areas but may not be typical of a completely healthy population.

Copeia↗
USGS2003

Pseudacris triseriata (western chorus frog) and Rana sylvatica (wood frog) chytridiomycosis

The chytrid fungus Batrachochytrium dendrobatidis is a known pathogen of anuran amphibians, and has been correlated with amphibian die-offs worldwide (Daszak et. al. 1999. Emerging Infectious Diseases 5:735-748). In Colorado, B. dendrobatidis has infected Boreal toads (Bufo boreas) (Muths et. al., in review) and has been identified on museum specimens of northern leopard frogs (Rana pipiens) (Carey et. al. 1999. Develop. Comp. Immunol. 23:459-472). We report the first verified case of chytrid fungus in chorus frogs (Pseudacris triseriata) and wood frogs (Rana sylvatica) in the United States. We collected seven P. triseriata, and two adult and two juvenile R. sylvatica in the Kawuneeche Valley in Rocky Mountain National Park (RMNP) during June 2001. These animals were submitted to the National Wildlife Health Center (NWHC) as part of an amphibian health evaluation in RMNP. Chorus frogs were shipped in one container. Wood frog adults and juveniles were shipped in two separate containers. Histological examinations of all chorus frogs and 3 of 4 wood frogs were positive for chytrid fungus infection. The fourth (adult) wood frog was too decomposed for meaningful histology. Histological findings consisted of multifocally mild to diffusely severe infections of the epidermis of the ventrum and hindlimb digital skin. Chytrid thalli were confined to the thickened epidermis (hyperkeratosis), were spherical to oval, and occasional thalli contained characteristic discharge pores or zoospores (Green and Kagarise Sherman 1999. J. Herpetol 35:92-103; Fellers et al. 2001. Copeia 2001:945-953). We cannot confirm that all specimens carried the fungus at collection, because infection may have spread from one individual to all other individuals in each container during transport. Further sampling of amphibians in Kawuneeche Valley is warranted to determine the rate of infection and mortality in these populations.

Colorado↗
USGS2003

A radio transmitter belt for small ranid frogs

Radio telemetry is a useful technique for gathering information about amphibians when associated caveats are applied (Bartelt and Peterson 2000). A number of designs for transmitter attachment are available for larger anurans including a harness-type attachment (van Nuland and Claus 1981) and various belt designs (Bartelt and Peterson 2000; Rathbun and Murphey 1996; Waye 2001). Attaching radios to small anurans is particularly problematic because of their mass, shape, and delicate skin. Small radios, 0.61 grams or less, are available, although battery life is usually only 2-3 wks (e.g., Holohil Systems Ltd; Carp, Ontario, Canada 1 ). The issues remaining are the weight and longevity of the attachment system, ease of application to the animal, and effect on the behavior and health of the animal. Here I describe an attachment assembly tested in the laboratory on juvenile leopard frogs ( Rana pipiens ) and used on wood frogs ( Rana sylvatica ) in the field.

Herpetological Review↗
USGS2002

Variable breeding phenology affects the exposure of amphibian embryos to ultraviolet radiation

Reduced water depth in dry years has been proposed to interact with ultraviolet- B (UV-B) radiation and a pathogenic fungus to cause episodes of high mortality of amphibian embryos. Observations of breeding phenology of boreal chorus frogs (Pseudacris maculata) in Colorado from 1986 to 2001 show that dry years result in earlier breeding. The earliest and latest dates of maximum calling activity by males were 20 May and 16 June, and the date of maximum calling was strongly related to the amount of snow accumulation during the winter. Surface UV-B flux, estimated from satellite-based measurements, was positively related to date of maximum calling. In dry years, surface UV-B during calling was reduced by an amount similar to that attributed to reduced depth. Although there was a significant trend of increasing UV-B from 1978 to 2001 on the average date (2 June) of maximum calling activity, there was no relationship between year and surface UV-B at actual dates of maximum calling. Exposure to extreme temperatures is an alternative explanation for increased mortality of amphibian embryos in shallow water.

Ecology↗
USGS2001

Secretion of whey acidic protein and cystatin is down regulated at mid-lactation in the red kangaroo (Macropus rufus)

Milk collected from the red kangaroo (Macropus rufus) between day 100 and 260 of lactation showed major changes in milk composition at around day 200 of lactation, the time at which the pouch young begins to temporarily exit the pouch and eat herbage. The carbohydrate content of milk declined abruptly at this time and although there was only a small increase in total protein content, SDS PAGE analysis of milk revealed asynchrony in the secretory pattern of individual proteins. The levels of ??-lactalbumin, ??-lactoglobulin, serum albumin and transferrin remain unchanged during lactation. In contrast, the protease inhibitor cystatin, and the putative protease inhibitor whey acidic protein (WAP) first appeared in milk at elevated concentrations after approximately 150 days of lactation and then ceased to be secreted at approximately 200 days. In addition, a major whey protein, late lactation protein, was first detected in milk around the time whey acidic protein and cystatin cease to be secreted and was present at least until day 260 of lactation. The co-ordinated, but asynchronous secretion of putative protease inhibitors in milk may have several roles during lactation including tissue remodelling in the mammary gland and protecting specific proteins in milk required for physiological development of the dependent young. ?? 2001 Elsevier Science Inc.

Conference Paper↗
USGS2001

Experimental repatriation of boreal toad (Bufo boreas) eggs, metamorphs, and adults in Rocky Mountain National Park

The boreal toad ( Bufo boreas ) is an endangered species in Colorado and is considered a candidate species for federal listing by the United States Fish and Wildlife Service. Boreal toads are absent from many areas of suitable habitat in the Southern Rocky Mountains of Colorado presumably due to a combination of causes. We moved boreal toads from existing populations and from captive rearing facilities to habitat which was historically, but is not currently, occupied by toads to experimentally examine methods of repatriation for this species. Repatriation is defined as the release of individuals into areas currently of historically occupied by that species (Dodd and Seigel, 1991). This effort was in response to one of the criteria for delisting the boreal toad in Colorado stated in the conservation plan and agreement for the management and recovery of the Southern Rocky Mountain population of the boreal toad (Loeffler, 1998:16); "...there must be at least 2 viable breeding populations of boreal toads in each of at least 9 of 11 mountain ranges of its historic distribution." Without moving eggs from established wild populations, or from captivity to historical localities, it is doubtful whether the recovery team will attain this ambitions goal.

Colorado↗
USGS2000

A comparison in Colorado of three methods to monitor breeding amphibians

We surveyed amphibians at 4 montane and 2 plains lentic sites in northern Colorado using 3 techniques: standardized call surveys, automated recording devices (frog-loggers), and intensive surveys including capture-recapture techniques. Amphibians were observed at 5 sites. Species richness varied from 0 to 4 species at each site. Richness scores, the sums of species richness among sites, were similar among methods: 8 for call surveys, 10 for frog-loggers, and 11 for intensive surveys (9 if the non-vocal salamander Ambystoma tigrinum is excluded). The frog-logger at 1 site recorded Spea bombifrons which was not active during the times when call and intensive surveys were conducted. Relative abundance scores from call surveys failed to reflect a relatively large population of Bufo woodhousii at 1 site and only weakly differentiated among different-sized populations of Pseudacris maculata at 3 other sites. For extensive applications, call surveys have the lowest costs and fewest requirements for highly trained personnel. However, for a variety of reasons, call surveys cannot be used with equal effectiveness in all parts of North America.

Northwestern Naturalist↗
USGS1996

Circulating levels of prolactin and progesterone in a wild population of red kangaroos (Macropus rufus) Marsupialia: Macropodidae

Circulating progesterone and prolactin levels were measured in shot and live-caught wild red kangaroos using radioimmunoassays validated for the red kangaroo. The objective of the study was to correlate hormone profiles with reproductive status and determine if red kangaroos follow the general pattern elucidated for other macropodids. During Phase 2a lactation (<70 days) plasma progesterone concentrations were <189 pg/ml ( n = 41). This value increased to >600 pg/ml ( n = 32) during the transition to Phase 3 lactation (181 to 235 days) when the quiescent corpus luteum and embryo were reactivated. Progesterone concentrations then decreased to <300 pg/ml ( n = 29) during dual lactation when females were suckling a neonate and a young at foot. Concentrations of prolactin during Phase 2a were <6 ng/ml ( n = 17). Coincident with the period of reactivation of the diapausing blastocyst (181 to 235 days), plasma prolactin concentrations increased to 15 ng/ml ( n = 32), then decreased and remained low through the subsequent stage of dual lactation. These results indicate that progesterone and prolactin profiles in wild red kangaroos follow patterns found previously in other macropodid species, the tammar and Bennett's wallabies.

General and Comparative Endocrinology↗
USGS1996

Kangaroo rat bone compared to white rat bone after short-term disuse and exercise

Kangaroo rats ( Dipodomys ordii ) were used to study the effects of confinement on mechanical properties of bone with a long range objective of proposing an alternative to the white rat model for the study of disuse osteoporosis. Kangaroo rats exhibit bipedal locomotion, which subjects their limbs to substantial accelerative forces in addition to the normal stress of weight bearing. We subjected groups of kangaroo rats and white rats ( Rattus norvegicus ) to one of two confinement treatments or to an exercise regime; animals were exercised at a rate calculated to replicate their (respective) daily exercise patterns. White laboratory rats were used as the comparison because they are currently the accepted model used in the study of disuse osteoporosis. After 6 weeks of treatment, rats were killed and the long bones of their hind limbs were tested mechanically and examined for histomorphometric changes. We found that kangaroo rats held in confinement had less ash content in their hind limbs than exercised kangaroo rats. In general, treated kangaroo rats showed morphometric and mechanical bone deterioration compared to controls and exercised kangaroo rats appeared to have slightly “stronger” bones than confined animals. White rats exhibited no significant differences between treatments. These preliminary results suggest that kangaroo rats may be an effective model in the study of disuse osteoporosis.

Comparative Biochemistry and Physiology, Part A: P↗