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The recent discovery of a pathogenic fungus (Batrachochytrium dendrobatidis) associated with declines of frogs in the American and Australian tropics, suggests that at least the proximate cause, may be known for many previously unexplained amphibian declines. We have monitored boreal toads in Colorado since 1991 at four sites using capture – recapture of adults and counts of egg masses to examine the dynamics of this metapopulation. Numbers of male toads declined in 1996 and 1999 with annual survival rate averaging 78 % from 1991–1994, 45 % in 1995 and 3 % between 1998 and 1999. Numbers of egg masses also declined. An etiological diagnosis of chytridiomycosis consistent with infections by the genus Batrachochytrium was made in 6 wild adult toads. Characteristic histomorphological features (i.e. intracellular location, shape of thalli, presence of discharge tubes and rhizoids) of chytrid organisms, and host tissue response (acanthosis and hyperkeratosis) were observed in individual toads. These characteristics were indistinguishable from previously reported mortality events associated with chytrid fungus. We also observed epizootiological features consistent with mortality events associated with chytrid fungus: an increase in the ratio of female:male toads captured, an apparent spread of mortalities within the metapopulation and mortalities restricted to post metamorphic animals. Eleven years of population data suggest that this metapopulation of toads is in danger of extinction, pathological and epizootiological evidence indicates that B. dendrobatidis has played a proximate role in this process.

From Library Journal Reading and Miller (Prairie Night: Black-Footed Ferrets and the Recovery of Endangered Species) are conservation biologists who present 49 case studies of endangered animals. The case studies are signed and represent the work of 70 individuals from 16 countries. They give the common name, scientific name, order, family, status, a list of threats, habitats, distribution, natural history, conflicting issues, and prognosis for each animal. They further provide a list of selected conservation organizations. An essay on the Yellowstone Grizzly Bear case by Tim W. Clark is also included, as is an essay by the editors. Gale's Encyclopedia of Endangered Species (LJ 1/95), which covers over 700 animals and plants, is obviously wider in scope, but it is less scholarly and extensive for the animals covered here. The Official World Wildlife Fund Guide to Endangered Species of North America (LJ 6/15/92. o.p.) is a solid tool but limited by region. The Grolier World Encyclopedia of Endangered Species (Grolier, 1992. o.p.) offers color pictures, which this lacks. Although the number of animals is limited, this guide is recommended for academic libraries requiring more detailed, scholarly information on specific animals and for the bibliography provided for each animal. Paul Haschak, Southeastern Louisiana Univ. Lib., Hammond Copyright 2001 Reed Business Information, Inc. --This text refers to the Hardcover edition.

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.

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 (Rathbun and Murphey 1996; Bartelt and Peterson 2000, Waye 2001). Attaching radios to small anurans is particularly problematic because of their mass, shape, and delicate skin. Small radios, https://0.61 grams or less, are available, although battery life is usually only 2 – 3 wks (e.g. Holohil Systems Ltd; Carp, Ontario, Canada ). 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.

Knowledge of the environmental constraints on a pathogen is critical to predicting its dynamics and effects on populations. Batrachochytrium dendrobatidis (Bd), an aquatic fungus that has been linked with widespread amphibian declines, is ubiquitous in the Rocky Mountains. As part of assessing the distribution limits of Bd in our study area, we sampled the water column and sediments for Bd zoospores in 30 high-elevation water bodies that lacked amphibians. All water bodies were in areas where Bd has been documented from neighboring, lower-elevation areas. We targeted areas lacking amphibians because existence of Bd independent of amphibians would have both ecologic and management implications. We did not detect Bd, which supports the hypothesis that it does not live independently of amphibians. However, assuming a detection sensitivity of 59.5% (based on sampling of water where amphibians tested positive for Bd), we only had 95%confidence of detecting Bd if it was in $16% of our sites. Further investigation into potential abiotic reservoirs is needed, but our results provide a strategic step in determining the distributional and environmental limitations of Bd in our study region.

We conducted a health survey of amphibians in and adjacent to Rocky Mountain National Park (RMNP) to document current disease presence inside RMNP and identify disease outside RMNP with the potential to spread to the Park’s amphibians. Amphibians from five sites within RMNP and seven sites within 60 km of Park boundaries were collected and examined. Necropsies (n = 238), virus isolation, bacterial and fungal cultures, and histological examinations were carried out on amphibian egg masses (outside RMNP/within RMNP: 26/22), larvae (30/42), imagos (recently metamorphosed individuals) (0/3) and adults (61/67) of five species. Marked infections by a pathogenic chytrid fungus (chyridiomycosis), Batrachochytrium dendrobatidis, were detected in three species (Bufo boreas, Pseudacris maculata and Rana sylvatica) from three of five sites within RMNP and in one of three species (P. maculata) from three sites outside RMNP. Of the fully metamorphosed individuals tested (B. boreas, P. maculata and R. sylvatica), chytridiomycosis was found in 60 % (n = 3), 46 % (n = 37) and 54 % (n = 7), respectively. Chytridiomycosis was the principal lethal pathogenic infectious disease detected in three amphibian species within or adjacent to RMNP. Higher fungi were isolated from the cloaca and skin of all five amphibian species. Watermolds (Oomycetes) were isolated from amphibian eggs or skin of all five species. No evidence of Ranavirus was found in cultures and histological examinations of 176 and 142 amphibians, respectively. Fifteen genera of bacteria were identified in larval and just metamorphosed amphibians, and a potentially pathogenic lungworm, Rhabdias sp, was identified in 61.1 % (n = 11) of B. woodhousii outside RMNP, but in only 2 (15.4 %) R. sylvatica within the Park.

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.

The Amphibian Research and Monitoring Initiative (ARMI) began in 2000 as an attempt by the United States Geological Survey to determine the status and trends of amphibians on federal lands in the United States and its territories. ARMI research focuses on determining causes of declines, if observed, developing new techniques to sample populations and analyze data, and disseminating information to scientists and policy makers. Monitoring is conducted at multiple scales, with an emphasis on an ability to draw conclusions about status in well-defined study areas such as national parks and wildlife refuges. Several papers originally presented at a national symposium in 2004 are published in this special issue of Alytes.

Corn and Muths (2002) described how seasonal and annual variation in estimated flux of ultraviolet-B (UVB)radiation, combined with year-to-year variation in amphibian breeding phenology, introduces considerable variability in the UV-B exposures to amphibians. The response to our paper by Blaustein et al. (2004)misstates the objectives and conclusions of our study, contains other errors of interpretation, and critiques our study for adopting practices that they themselves use. We are confident that an unbiased assessment will show that the conclusions of Corn and Muths (2002) are valid and robust with respect to montane amphibians, and that the criticisms raised by Blaustein et al. (2004) are either invalid or irrelevant.

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.

The Rocky Mountain Region of the United States Geological Survey’s Amphibian Research and Monitoring Initiative is conducting monitoring of the status of amphibians on a transect that extends along the Continental Divide from Canada to Colorado and comprises four National Parks. Monitoring uses visual encounter surveys to determine site occupancy, with multiple visits to a subset of sites to estimate detection probabilities for each species. Detection probabilities were generally high (above 0.65) among species. There was a gradient in site occupancy, with most species scarce in the south and relatively common in the north. For example, Bufo boreas is close to extinction in Rocky Mountain National Park, was found at fewer than 5 % of sites in Yellowstone and Grand Teton National Parks in the middle of the transect, but occurs at approximately 10 % of sites in Glacier National Park. The salamander Ambystoma tigrinum was rare in Rocky Mountain and occurred at less than 25 % of sites at Yellowstone and Grand Teton, but A. macrodactylum occurred at more than 50 % of sites in Glacier. There are numerous differences among parks, such as latitude, climate, numbers of visitors, and human population density in the surrounding landscape. The degree to which these factors have influenced the current distribution and abundance of amphibians is unknown but should be a focus of additional research.

Book chapter that discusses specific limitations to the recovery of boreal toads from population declines in Colorado.

The chemical composition of 97 lakes and ponds in and near the Mount Zirkel Wilderness Area (MZWA) was studied during snowmelt of 1998 and 1999 to determine the magnitude of episodic acidification and the effects of acidification on amphibian reproductive success. Within the areas identified as sensitive to acidification based on granitic bedrock types, there was substantial variability in ANC that was likely related to differences in hydrologic flowpaths that control delivery of weathering products to surface waters. Many of the lakes are sensitive to acidification (summer and fall ANC< 100 eq/l), however, none of them appeared to be immediately threatened by episodic or chronic acidification. 22 ponds had minimum ANC of < 30 ueq/l, indicating that they are extremely sensitive to acidic deposition, however net acidity (ANC < 0) was not measured in any of the ponds. 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 measured during the study.

Rocky Mountain National Park (RMNP) has historically been a home to boreal toads (Bufo boreas boreas). Since the 1970s the number of toad populations in Colorado and in the Park has declined. Now there are only three locations where breeding is occurring in RMNP. The USGS Fort Collins Science Center has been studying boreal toads in RMNP for over 15 years and has documented population declines coincident with the detection of the amphibian chytrid fungus.

After 4 years of surveys, disease testing, and planning specific to this effort, RMNP is collaborating with USGS and the Colorado Division of Wildlife to reintroduce boreal toads to a site on the west side of the Park. The site is typical of historical toad habitat in the park, has only a small population of chorus frogs (Pseudacris maculata), no evidence of the amphibian chytrid, and no fish. Although most of the wetland dries by the end of summer, deeper waters in the middle provide a refuge for late-developing amphibian larvae. Boreal toad tadpoles do not overwinter, and therefore must grow and metamorphose before the onset of freezing temperatures and snow, making this water refugia important.

This year over 14,000 tadpoles were released by a team of over 40 volunteers on June 25th. This exercise involved carrying plastic bags filled with water and about 300 tadpoles per bag up two miles of trail and into the site. The tadpoles were hatched at the Colorado Division of Wildlife’s Native Species Hatchery in Alamosa, Colorado. The parents of these tadpoles were wild caught boreal toads from RMNP.

This effort involved over 40 volunteers including representatives from the Park Service, U.S. Geological Survey, Bureau of Land Management, U.S. Forest Service, Colorado State University, the Colorado Division of Wildlife and non-governmental agencies.

This was Year 1 of the planned three years of tadpole releases for this site. Boreal toads, if they can survive the tadpole stage and successfully metamorphose, take three to four years to reach sexual maturity and return to their natal pond to breed. Tracking these tiny toads is extremely difficult between metamorphosis and their return to the pond. Multiple releases over several years increase the chances that some will survive and return to breed, and is patterned after a successful reintroduction of Natterjack toads in England.

In addition to the tadpoles, seven adult boreal toads, animals that were in excess of those needed for the captive breeding stock at the hatchery, were also released. These animals, four males and 3 females, were released in early summer after receiving a hormone injection to encourage breeding. Each animal was fitted with a radio transmitter and will be tracked 2 to 3 times per week over the summer until autumn when the batteries on the transmitters will be drained.

Tadpoles are generally considered the best lifestage to use for reintroduction efforts; however, releasing adults also can be advantageous. Released adults can act as “sentinels” to detect disease, particularly the amphibian chytrid fungus. Although the site was tested using non-invasive swabs from captured chorus frogs as well as a newer technique to test the water for this fungus, the lack of a positive test does not provide certainty that the site is disease-free. Having adult toads in the habitat gives researchers the opportunity to monitor susceptible animals for the disease over the course of time. Each animal will be tested every week for the amphibian chytrid fungus and, if the organism is found, this information will be used in determining the course of the reintroduction effort. In addition to serving as sentinels for disease, released animals are being followed closely to determine how they respond to their new habitat, how they make use of it, and how far they roam from it – all critical information for other reintroduction efforts with adult amphibians. Information collected on the released adults, such as body temperature and micro-habitat characteristics, is contributing to another collaborative study (Idaho State University and USGS) on boreal toads that is focusing on toad and site temperatures in relation to the amphibian chytrid fungus at sites in Colorado and Wyoming.

Overall, the multi-year reintroduction of tadpoles and adult boreal toads represents an extraordinary example of inter-agency cooperation in working towards the recovery of a state endangered amphibian.

For further reading:

Muths, E., Corn, P.S., Pessier, A.P., and Green, D.E., 2003, Evidence for disease related amphibian decline in Colorado: Biological Conservation, v. 110, p. 357–365.

Muths, E., 2003, Homerange and movements of boreal toads in undisturbed habitats: Copeia, v. 2003, no. 1, p. 161–165.

Denton, J.S., and Beebee, T.J.C., 1996, Habitat occupancy by juvenile natterjack toads (Bufo calamita) on grazed and ungrazed heathland: Herpetological Journal, v. 6, no. 2, p. 49–52.