Amphibians are an important part of Yellowstone’s aquatic and terrestrial ecosystems. Many of Yellowstone’s reptiles, birds, mammals, and fish prey on larval and adult amphibians and amphibians, in turn, eat a variety of vertebrate and invertebrate species. Amphibians are also sensitive to disease, pollution, drought, variations in annual snowpack, and the arrival of nonnative species; these documented sensitivities make them valuable indicators to environmental change. Amphibians often congregate in large numbers for breeding or overwintering. As a result, they can be adversely affected by localized disturbance or the loss of individual breeding or overwintering sites. Amphibian populations that are affected by one or more of these stresses may exhibit changes in their distribution or abundance. These changes can, in turn, have cascading effects on other aspects of the ecosystem.
Declines in amphibian populations are occurring globally in areas where habitat destruction is pervasive, but also in protected areas. About one- third of all amphibian species are believed to be threatened with extinction. Yellowstone includes some of the most climatologically and topographically complex landscapes in the lower 48 states and therefore provides a valuable study area to examine how climate may influence amphibian distribution and trends. Information about the status and trends of amphibians here may shed light on declines documented in other high-elevation locations or other protected areas around the West.
In 2015, a breeding population of plains spadefoot toads was confirmed in Yellowstone.
Annual surveys since the early 2000s have documented four amphibian species as widely distributed in Yellowstone: boreal chorus frogs, Columbia spotted frogs, western tiger salamanders, and western toads occur in wetlands and ponds throughout Yellowstone. In 2014, the plains spadefoot (Spea bombifrons) was confirmed in Yellowstone through genetic analyses. These toads are rarely seen because they spend most daylight hours underground. Currently, a single breeding population is known to exist within Yellowstone. However, monitoring efforts are underway to locate additional breeding sites because plains spadefoots typically do not disperse far from their natal pond.
In Yellowstone, amphibians depend on limited suitable habitat with shallow, quiet waters needed for egg laying and larval development. Annual differences in snowpack and precipitation change the extent and location of wetland sites, resulting in considerable year-to-year variation in amphibian reproduction. Breeding data collected across the park and since 2006 show that annual variations in breeding are common. Multi-year monitoring data indicate that amphibian populations using small, shallow isolated wetlands are most susceptible to drought or changes in precipitation. In contrast, amphibian populations occupying deeper wetlands and ponds appear to be more stable through time.
Since the 1950s, air temperatures have increased across this region and changes in the flooding pat- terns or the complete drying of wetlands have been documented. Since 2006, annual visits to approximately 250 wetlands across Yellowstone have further documented annual variation in the availability of wetlands. This data suggests that in hot dry years (e.g., 2007) upwards of 40% of the park’s wetlands dry up. In cool, wet years (e.g., 2011) most wetlands across the park are flooded and available to support amphibian breeding. Further warming is anticipated for this region and could contribute to the drying of wetlands and influence the distribution and abundance of amphibians and other wetland dependent species.
Disease agents, such as ranavirus and chytrid fungus (Batrachochytrium dentrobatidis), could also affect the survival and reproduction of amphibian populations in Yellowstone. Ranavirus has been found in tiger salamanders and Columbia spotted frogs collected from die-offs since 2008 and been involved with die-offs of all four widely distributed species in the region. Chytrid fungus does not necessarily cause a fatal infection and usually appears in Columbia spotted frogs and western toads following metamorphosis. The DNA of the chytrid fungus has been identified in skin swabs collected from both species in Yellowstone, though the impacts at the population level have not been determined. Since 2015, 44% of tissue samples (tail clips) collected from larval amphibians (frog and toad tadpoles) have tested positive for ranavirus. These findings highlight that several factors, including host susceptibility and environmental conditions, may determine whether an infection is lethal and results in a die-off or a decline in population abundance.
Number in Yellowstone
5 species: Western tiger salamander, boreal chorus frog,Western toad, Columbia spotted frog, and plains spadefoot toad.
Toads are not taxonomically different from frogs. The species called “toads” are associated with drier skin and more terrestrial habitats.
Columbia spotted and boreal chorus frogs are widely distributed with many breeding sites in the park.
Western tiger salamanders are common and abundant on the northern range and Hayden Valley.
Western toads are abundant in some local areas.
None of the park’s amphibians are federally listed as threatened or endangered.
Scientists are concerned about the Western toad, which has declined sharply in other parts of the West.
2000: Researchers begin inventorying amphibians.
2005: Long-term amphibian monitoring begins in Yellowstone.
2014: A breeding population of plains spadefoot (Spea bombifrons) was confirmed near Fountain Flat Drive.
Survival in Winter
To survive the winter, some Yellowstone amphibians go into water that does not freeze (spotted frogs), others enter underground burrows (salamanders and toads), and others (boreal chorus frog) tolerate freezing and go into a heart-stopped dormancy for the winter in leaf litter or under woody debris.
Studying Amphibians in Yellowstone
The Greater Yellowstone Network (GRYN) has led a collaborative monitoring of wetlands and amphibians in Yellowstone since 2006. Long-term monitoring of amphibian populations provides an opportunity to observe trends that may not be apparent at local scales or in areas with more direct human influences on habitat quality.
Amphibians are monitored at catchments (or watersheds), which average approximately 500 acres in size. On average, 30 catchments are revisited during annul monitoring visits. All wetlands within the selected catchment are visited each summer, when two independent observers search for amphibians breeding evidence (i.e., eggs, larvae, or recently metamorphosed individuals) and document important habitat characteristics and the presence or absence of surface water.
The objectives of GRYN’s annual monitoring are to estimate the proportion of monitored catchments and wetlands used for breeding by each native amphibian species annually, to consider whether the rate and direction of use may be changing through time, and to document the number of wetlands within catchments that are potentially suitable for amphibian breeding.
This annual monitoring is then combined with local climate data to carefully examine the links between climate, wetlands, and amphibians. Taken together, amphibian and wetland monitor- ing data from the last decade, coupled with local climate information, will help support predictions of amphibian occurrence under different climate scenarios.
Explore some sights and sounds of amphibians in Yellowstone.
A chorus of uncommon spadefoot toads call during springtime in the park. These toads are named for their spade like feet that they use to dig their burrows deep underground in order to overwinter. The toads sing during breeding season, especially following heavy rains.
/Natural sounds of frogs chirping/ I remember walking out of the house in the afternoon and I heard the most amazing sound. and it seemed to be coming from everywhere because it was so loud. I eventually wandered down to a lovely little riparian area near the housing and I still couldn't figure out what was making the sound. How can you have so much sound and not see what it is? The boreal chorus frog is really common in Yellowstone, but they're such an uncommon animal. They are very small...a huge male is only an inch and a half long. And they have a special adaptation that there bodies can nearly freeze, and yet they are not damaged when they thaw out. Which is a cool thing, but it also means that if we can figure out how it works, this may help humans who have suffered severe hypothermia or other damage to their bodies from extreme cold. I'm ranger Rita Garcia. I'm an interpretive park ranger at Yellowstone National Park.
If you've visited Yellowstone during spring, you've probably heard the all-male chorus of the boreal chorus frog: but actually seeing them is another matter. Ranger Rita Garcia reminisces about discovering these tiny amphibians for the first time.
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