Small Variations in Breeding Pools Make for Big Differences in Yosemite Toad Use

Researchers have discovered that Yosemite toads have surprisingly fine-scale preferences when selecting alpine meadow pools for breeding.

The Yosemite toad (Anaxyrus canorus) is a rare species found exclusively in California’s Sierra Nevada. While its range encompasses hundreds of miles, spanning five national forests and two national parks, the livelihood and future survival of this federally threatened species may come down to mere centimeters.

According to research by the U.S. Forest Service’s Pacific Southwest Research Station and its collaborators, for pools within alpine meadows to be suitable habitat for laying eggs and sustaining tadpoles, little things mean a lot.

“Our research looked at pools across the toad’s range, in a variety of weather and precipitation conditions across a number of years,” said Christina Liang, a research ecologist with the Pacific Southwest Research Station and lead author of the study. “But no matter the year-to-year variations, we found relatively consistent and definitive characteristics were shared by the majority of pools supporting Yosemite toad offspring compared to those unoccupied.”

As the snow pack begins to recede across the Sierras, now is the time mating pairs of Yosemite toads seek out pools with the right mix of length and width, depth, vegetation and temperature to bring forth the next generation of toadlets. In Liang and her colleagues’ study, “Fine-Scale Habitat Characteristics Related to Occupancy of the Yosemite Toad,” they found the following differences, on average, between occupied and unoccupied pools:

  • Depth of bottom debris: 1.62 cm (occupied) versus 1.69 cm (unoccupied)
  • Pool vegetation height: 13.20 cm versus 14.16 cm
  • Water depth: 4.35 cm…

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