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Little is known about use of burned habitat by post-breeding adult western toads. In this study, I examined adult western toad use of the habitat mosaic created by a recent wildfire on the west side of Glacier National Park.

Prey species that occur across a range of habitats may be exposed to variable communities of multiple predator species across habitats. Predicting the combined effects of multiple predators can be complex. Many experiments evaluating the effects of multiple predators on prey confound either variation in predator density with predator identity or variation in relative predator frequency with overall predation rates. We develop a new experimental design of factorial predator combinations that maintains a constant expected predation rate, under the null hypothesis of additive predator effects. We implement this design to evaluate the combined effects of three predator species (bass, aeshnid and libellulid odonate naiads) on mortality rate of a prey species, Hyla cinerea (Schneider, 1799) tadpoles, that occurs across a range of aquatic habitats. Two predator treatments (libellulid and aeshnid + libellulid) resulted in lower tadpole mortality than any of the other predator treatments. Variation in tadpole mortality across treatments was not related to coarse variation in microhabitat use, but was likely due to intraguild predation, which occurred in all predator treatments. Hyla cinerea tadpoles have constant, low survival values when exposed to many different combinations of predator species, and predation rate probably increases linearly with predator density.

We examined 142 papers, which contained 603 separate predator-prey trials, to investigate whether unpalatability is an important defense against predation for amphibian eggs and larvae. Although unpalatability is often cited as an antipredator defense, it was rarely demonstrated that 89% of the trials that we reviewed found prey to be palatable. The most extensively studied taxa, the genera Bufo and Rana, were diagnosed unpalatable at rates comparable to all other taxa. Diagnoses of unpalatability were not always consistent for a prey species across different predators and were influenced by experimental method. Despite these limitations and our conservative definition of unpalatability, several patterns emerged. First, across all taxonomic groups, eggs and hatchlings were unpalatable more often than mobile larval stages. Second, species that breed in temporary ponds were more likely to be palatable to fish predators than those that breed in permanent habitats. Third, fish and caudates were more likely to find amphibian prey unpalatable than insect predators. We conclude that unpalatability is rare, but when it occurs, it is a property of an ensemble (predator, prey, and alternative prey) and a life-history stage in a particular circumstance but is not a species specific attribute. We suggest methods of experimentation that could strengthen future research on the palatability of amphibian eggs and larvae.

Information on life-history traits is critical to understanding population dynamics of anurans. The objective of this study was to examine aspects of the reproductive ecology of Hyla cinerea in northwestern Florida. Four breeding localities in Leon County, Florida, were sampled over three seasons (2001–2003), amplexed pairs were found as early as 12 April and as late as 12 August. Egg clutches were counted from 51 amplexed pairs and adult size was measured in 43 pairs. Average clutch size was 1214 ± 528 eggs ( ± se, range = 359–2658). Female H. cinerea were slightly larger than males ( ± se tibiofibula length = 24.9 ± 2.2 and 24 ± 1.7 mm, respectively). Female size was significantly positively correlated with clutch size and weakly correlated with size of the paired male. Comparison of the results of this study with previous research indicates that the reproductive ecology of H. cinerea varies across its geographic range.

Long-term effects of hybridization and introgression are influenced by performance of hybrids in habitats of parental species. The treefrogs Hyla cinerea and Hyla gratiosa, which typically breed in permanent and temporary habitats, respectively, have occasionally hybridized throughout the Southeastern United States. To predict in which of the parental habitats effects of hybridization might be strongest, I performed experiments to evaluate predation on tadpoles of H. cinerea, H. gratiosa, and F1 hybrids with predators typical of the breeding habitats of the parental species. Hybrid tadpoles had lower survival with sunfish than odonate naiad (dragonfly) predators and tended to increase hiding behavior in response to sunfish predation. Tadpoles of H. gratiosa also had higher survival with odonates than sunfish, but H. cinerea had similar survival with both predator types. These results suggest that hybrids are most likely to survive and return to breed in temporary habitats used by H. gratiosa. Thus, hybridization and introgression might be more likely to have adverse effects on populations of H. gratiosa than H. cinerea.

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 conducted health screenings for infectious diseases of amphibians at four warm-water fish hatcheries and one National Wildlife Refuge in the southeastern United States. We confirmed the presence of Batrachochytrium dendrobatidis (amphibian chytrid fungus) in Rana catesbeiana (American Bullfrog) from one hatchery, as well as potentially new species of microsporidian and myxozoan parasites infecting all 10 amphibian species sampled. Viruses were not found in tissue cultures or histologically. Tens of thousands of individual amphibians may breed in outdoor warm water fish-rearing ponds. Although there have been no reports of disease outbreaks at the sampling sites, the potential transmission of infectious diseases between amphibians and fishes could have serious consequences for amphibian populations at recipient sites.

The amphibian chytrid fungus Batrachochytrium dendrobatidis, responsible for the potentially fatal amphibian disease chytridiomycosis, is known to occur in a large and ever increasing number of amphibian populations around the world. However, sampling has been biased towards stream- and wetland-breeding anurans, with little attention paid to stream-associated salamanders.
We sampled three frog and three salamander species in the Chesapeake and Ohio Canal National Historic Park, Maryland, by swabbing animals for PCR analysis to detect DNA of B. dendrobatidis.
Using PCR, we detected B. dendrobatidis DNA in both stream and wetland amphibians, and report here the first occurrence of the pathogen in two species of stream-associated salamanders. Future research should focus on mechanisms within habitats that may affect persistence and dissemination of B. dendrobatidis among stream-associated salamanders.