Site visit insights: Thunderstorms, hail and elusive Yosemite toads

By the U.S. Fish and Wildlife Service

Biologists from the Sacramento and Reno Fish and Wildlife Offices and the U.S. Forest Service collaborate on a Yosemite toad monitoring site visit. ©Rick Kuyper

Site visits are critical to helping scientists learn more about species and their habitats.  The trips often take them into areas most people do not have a chance to explore, including public and privately-owned restricted sites, as well as some remote and hard-to-reach areas.  “Site visit Insights” provides a behind-the-scenes perspective of wildlife biology, featuring photographs and interesting discoveries and happenings biologists experience in the field.

In cooperation with the U.S. Fish and Wildlife Service, The Wildlife Society is pleased to share these insights.

Wildlife Biologist: Rick Kuyper, chief, Sierra Cascades Division, Sacramento Fish and Wildlife Office
Site visit location: Toiyabe National Forest

What was the purpose of the site visit?

SFWO Biologist Becky Kirby and I were invited by the Reno Fish and Wildlife Office to meet with U.S. Forest Service Biologist Rachel Van Horne to participate in Yosemite toad (Anaxyrus canorus) monitoring activities on the Toiyabe National Forest.

Yosemite toads are difficult to find during most of the year because they prefer to remain hidden. They spend a lot of time underground in burrows for example. In the spring, the snow begins to melt, which creates ponds that the toads use for breeding and laying eggs. This usually lasts for only a week. We were able to see breeding toads, egg masses, and one-year-old juveniles in several different ponds. During our site visit, Becky and I helped collect male toads for a pit-tag study. A small “chip” is placed under the skin of the toads, giving each toad a unique identification number. When the toads are caught they are scanned to see if they already have a chip. And if they do, we are able to determine if toads have moved from one area to another, the age of toads, and we can estimate population sizes. All of this information allows us to understand how well toad populations are doing and the Forest Service can use this information to help inform land management decisions.

Where did you go?

We were on the Toiyabe National Forest, on the east side of the Sierra Nevada, in the Sonora Pass area. As we drove to the site, we could see the northern edge of Yosemite National Park. The elevation was around 9,000 feet.

What partners were you working with and what is the nature of SFWO’s partnership with them?

We worked with biologists from the Reno Fish and Wildlife Office and the U.S. Forest Service. The Reno office works closely with the Toiyabe National Forest because this forest is within its jurisdiction; but SFWO is the “species lead” for Yosemite toad, so the Reno FWO biologists invited us out to see the toads. We work closely with our colleagues in Reno and the Forest Service throughout the Sierras on many species, including Yosemite toads and Sierra Nevada yellow-legged frogs.

What did you learn from this site visit that you didn’t know before?

This was the first time Becky and I were able to observe Yosemite toads. With our job, it is essential to see the species up close in their habitat. Just observing the toads and seeing how they spend the day was extremely informative. We watched breeding behaviors, we could see where the females preferred to lay their eggs, we observed males sitting in burrow openings, and countless one-year-old juveniles hopping all over the place along the outer edges of the ponds. We had to walk with great care to make sure we weren’t stepping on any of the little juveniles.

What surprises did you encounter during the site visit?

Going in I knew that toads are well camouflaged and difficult to see, but I was still surprised at how hard it was to see them unless they moved. If they hold perfectly still you’ll walk right past them. At first it was hard to find them, but then your eyes get a search image and you start seeing toads more easily. The eggs were especially difficult to see. We marked the egg masses with red flags so we wouldn’t accidentally step on them. When the males are calling for females, it gets loud but as you approach the pond they stop calling and everything becomes perfectly quiet for a few moments and then they start up again.

Because Yosemite toads breed in remote meadows in the Sierra Nevada Mountains, it’s difficult to time your visit just right.  They’re only congregating together for a few short days during the year, and then they head away from the wet meadows into the forests and they are rarely seen until the next snowmelt. Being there during this small window is an unforgettable experience.

There was still a lot of snow on the ground. The toads manage to survive during the winter hunkered down in burrows and they had to wait a little extra long this year for the snow to melt.

We were also treated to afternoon thundershowers and a hail storm.

Yosemite toads are difficult to find during most of the year because they spend a lot of time underground in burrows. ©Rick Kuyper

Mating and egg-laying take place from May to July, shortly after the snow melts in shallow pools in meadows, on the margins of lakes and quiet streams. ©Rick Kuyper

Male Yosemite toads set up a territory in shallow water and make a trilled breeding call to attract a female. Part of the species name, “canorus” means ‘tuneful’ in Latin, referring to the male’s sustained melodious trill. ©Rick Kuyper

Yosemite toads have the largest size difference between males and females of any other North American frog or toad. ©Jill-Marie Seymour

To help monitor the Yosemite toads, a small chip is placed under their skin, giving each toad a unique identification number. Scanning the chip reveals if toads have moved from one area to another, the age of toads, and population size estimates. ©Rick Kuyper

The U.S. Fish and Wildlife Service is a Strategic Partner of TWS.