What follows are remarks by Debra Patla. She has been studying wild amphibians in the Greater Yellowstone Ecosystem since 1993 as a Northern Rockies Conservation Cooperative research assistant and field coordinator for amphibian monitoring in Grand Teton and Yellowstone national parks. This year the Meg and Bert Raynes Fund supported her work on amphibians on the National Elk Refuge. I asked Deb to say a bit about how these animals get through winter in Jackson Hole:
In late summer and early fall people in Jackson Hole are sometimes astonished to encounter an amphibian — a frog, toad or salamander — in unexpected places. On the trail, in the garden, in the garage or even in the house … there hops or crawls an animal you may never have before seen, even after years of living here. Or the encounter may be acoustic. On a quiet afternoon one trilling voice calls out from the ground, and “frog?” seems the best guess.
Is the creature lost, somehow displaced from its home pond? Is it a released, unwanted pet? The most likely answer is that you have found a native wild amphibian en route to a place where it can survive the coming harsh Jackson Hole winter.
Our list of native amphibians is short: boreal chorus frog, Columbia spotted frog, boreal toad and tiger salamander. These species depend on shallow water to breed and deposit their eggs, but what they do the rest of the year is distinctive.
The Columbia spotted frog is the only species that winters in water, seeking out spring-fed aquatic features that will not freeze or become depleted of oxygen. Tiger salamanders and boreal toads go underground, down below the frost zone, into natural cavities or the burrows and tunnels of other animals, which they may enlarge by wriggling. The tiny boreal chorus frog stays closer to the surface, where it works a wonder of nature by freezing for days or weeks in the coldest times of winter. Freeze tolerance is accomplished when the frogs make a kind of antifreeze to protect vital organs, while water in the body outside the cells freezes up. (It takes many environmental cues to pull this off. Do not put frogs in your freezer!)
Amphibians you meet in the fall are probably migrating from their breeding sites or summer foraging areas to their winter retreats. The distance of amphibian migrations varies, not only with respect to species, sex, age and the environmental setting but also among individuals. Biologists have found seasonal movements to be mostly less than 500 yards but have also seen examples of much longer movements, well over a mile for some species here.
Amphibians have a strong sense of “home,” specific places where an individual will breed and winter during its lifetime. Local amphibians may live 12 years or more. The amphibian you encounter most likely has a destination in mind or could be making an exploratory foray to expand its range.
Juvenile amphibians, however, may disperse randomly across the landscape in the weeks after they metamorphose from tadpoles. A spectacular example was witnessed this year near a picnic area in Grand Teton National Park, north of Colter Bay. The picnic area, on dry land above Jackson Lake, was inundated by a host of tiny boreal toads starting at the end of August.
Park staff quickly and admirably responded by blocking vehicle access to keep the toads from being crushed, and posting a sign about the toad event. These toadlets were apparently moving in vast numbers from their birthplace in a shallow bay of the lake, 500 yards to the south. They traveled up steep banks, through the forest, across a thickly willowed stream and along the lake shore. Going … who knows where? With luck, journey’s end was a good place to go underground for the winter. Field studies elsewhere suggest some, perhaps the majority of survivors, will return to breed at the same bay when they grow up in three to five years. But some may find new places, establishing new breeding populations. This phenomenon gives us a peek at how amphibians originally spread across Jackson Hole after the Ice Age glaciers retreated.
How amphibians navigate and find “home” is a fascinating subject. Explanations include vision and smell, memory, genetic inclinations, celestial (mostly solar) guidance, magnetic orientation and perception of polarized light. No one knows how frogs integrate all that information.
What to do when you encounter an amphibian? Move it out of harm’s way if you can, such as off the pathway or away from pets, preferably in the direction you think it was moving, into natural vegetation. Trust that it knows where it is going; don’t move it far. And don’t forget to put your observation in Nature Mapping. Conservation of these tiny, tough wildlife depends on protecting their migration zones and winter sites as well as the wetlands where we will find them gathered in the spring.
Field Notes: It’s October. No more speculation about whether autumn has arrived; it’s when will winter hit. Leaf color is subdued, or trees are bare. Still, some are greenish or are yet to turn. I thought recent heavy rain would have taken more leaves down; wrong again.
Birds and animals are doing their Fall Shuttle, heading to winter quarters. Bears are in the news, and in settlements. Mice are looking to domicile in domiciles. Hummingbirds are gone. Blackbirds are flocking (Susan Patla).
A host of coots and some associated waterfowl arrived on Flat Creek overnight on Sept. 30-Oct. 1 (Chuck Herz and others). Twenty-two juvenile grebes were stranded on Jackson airport Friday evening, Sept. 26, disoriented in rain and low fog. Unable to take off again, rescued by airport and Grand Teton National park personnel.
Swainson’s hawk coming down: Ben Hahn spotted one on Oct. 1. Autumn is happening.