Mary Greenblatt- Amphibian Monitoring

The amphibian field crew balances on a beaver dam to cross the wetland.

 

This young chorus frog is one of the park's native amphibians.

You might wonder what a day of amphibian monitoring looks like? In Grand Teton National Park, we usually monitor our wetlands spending one to several days in each catchment. Except for one catchment in the northern part of the park, we monitor most sites without spending nights in the backcountry. Our catchments consist of multiple wetland areas that are grouped together by proximity. We visit these areas or catchments once a year to survey the wetlands. Our visits consist of two independent surveys spaced fifteen minutes apart. During the survey we walk all around the wetland looking for the presence of this year’s young, known as tadpoles or larvae depending on whether we find frogs, toads, or salamanders. We also record the presence of any adult amphibians or reptiles; the air and water temperature; and water depth, length, width, and area using a GPS. We retake the wetland photo from the same exact spot annually. We record all this information on a field form noting habitat information and any changes we observe compared to previous years. some frequent examples are whether the wetland has changed in size or if there is fresh beaver sign.

 

Park wetlands provide habitat and hiding places for this Columbian spotted frog and other amphibians to conceal themselves from predators like herons.

The third week of June is the time for our annual amphibian survey at Sawmill Ponds near Moose. Wearing chest waders, carrying large day packs, and what looks like butterfly nets; we descended the rocky slope to the water’s edge near the overlook. The biggest question on our minds in this notably hot and dry month was had the beavers returned? If the beavers returned and worked on their dams or built new dams this would presumably impound more water creating larger wetlands for us to survey during our annual search for amphibians. We found that indeed the beavers had returned and created larger wetlands for us to survey! While much larger wetlands can sometimes make it harder to detect amphibians, it also creates more habitat for amphibians to breed. Overall, the summer of 2021 revealed that wetlands in Grand Teton and Yellowstone National Parks, that were not beaver influenced, were dryer than in recent years. At Sawmill Ponds, we observed active beaver sign with more water present than in the previous year. In our field notes we suggest that we allow an extra day for amphibian surveys at Sawmill Ponds in 2022. Normally our survey team is small, just me and one additional field partner, but occasionally for the bigger wetlands we use a crew. With additional help, we will be able to survey the same wetlands in two days instead of three and a half days.

 

Tiger salamander larvae are identified by their feathery external gills.

Sawmill Ponds are spring influenced and located along the historic floodplain of the Snake River. The area is rich in wildlife including moose, elk, deer, sandhill cranes, great blue heron, and fox, among other species. It is also the only wetland complex we survey where all four native species of amphibians are found in Grand Teton National Park (Columbia spotted frog, western tiger salamander, boreal chorus frog, and western toad). Interestingly, we have only found western toad tadpoles at Sawmill Ponds when the beavers are active and working on their dams.

When beavers have recently worked on their dam, it can have so much fresh mud that we are afraid to cross it during our survey because the mud is still wet and slippery. If their activity has increased the wetland significantly, we occasionally change a few of our repeat photo points because the water was too deep for our chest waders (which means above waist high/chest high). In areas recently flooded by beaver activity, we will find all sorts of plants including dandelions and mushrooms submerged under the much deeper water that we are surveying.

Beaver dams hold back water, spreading it across the floodplain and creating more breeding habitat for toads and other amphibians. The abundance of water allows vegetation to grow taller and lusher than a dry wetland. With more water the sedges grow taller and become a challenge because as the wetlands dry out the sedges become dry and sharp or ‘angry’ as we like to say. Visiting the wetlands in the drying season always reminds me of the well-known identification rhyme, “Sedges have edges…” and how sharp those edges can be.

 

This frog morph has grown all four legs but has yet to absorb the tail from its tadpole stage.

We returned to Sawmill Ponds in mid-July for water samples. We collect water to determine whether amphibian DNA was present in the surface waters of the ponds. Environmental DNA (eDNA) as it’s known, allows for the detection of amphibians and other organisms from DNA present in water samples. When we returned in 2021, the vegetation had grown so tall it was harder to access the wetlands we visited just a few weeks earlier. Elsewhere in the park, many wetlands were dry. Because of the beaver activity, water was still standing across much of the Sawmill Ponds and Snake River floodplain areas. Stimulated by the moisture, reed canary grass, present because this area was historically homesteaded, was almost six feet tall! This is about two or three feet taller than the previous month. Sawmill Ponds is such a rich and productive wetland not just for amphibians but for many species of plants and wildlife. We are glad that we survey in June before the vegetation gets taller than we are!

 

Mary half hidden by the lush growth of wetland plants.

Seeing this made me think that I had been visiting this wetland over fifteen years, long enough to see it change once again. Now the next question is just how much will change in this catchment before next July? Only time will tell us how long and how active the beavers will be at our catchment or if they will return at another catchment we survey? Seeing these changes and just how much beavers influence our wetlands and create habitat for many other species makes me excited for another field season.

Mary Greenblatt, Amphibian Field Biology Technician
Northern Rockies Conservation Cooperative Partner