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E. Muths

Publications and source records attributed to E. Muths.

27 records · Page 2Linked to original sources
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↗