Orange County Register

If you hike or bike the historic Irvine Ranch, you might see something new on the trail: artificial pools scooped out by scientists for the hard-pressed spadefoot toad.

The pools could turn out to be a matter of life and death.

Signs posted at the pools offer an explanation, and the scientists, from the U.S. Geological Survey and the Irvine Ranch Conservancy, hope for buy-in from the public in their campaign to save the toads.

“We know that they’re using some pools that have been created in road ruts,” said Susie Anon, field ecologist with the conservancy. “It’s kind of a problem, because they get run over.”

The scientists dug 15 pools altogether, three sets of five, in Crystal Cove State Park and Laguna Coast Wilderness Park, Anon said. 

 ”For the most part, they are along used roads and trails,” she said.

While not listed as endangered, spadefoots are considered a state species of special concern. The toad’s roadside habits are bringing it into conflict with humans, with the toads on the losing end.

The strategy worked wonders for millennia: lay eggs in temporary pools during Southern California’s brief rainy season, then hide underground when it’s dry.

The aptly named spadefoot toads are even equipped with a tiny spike on their rear feet, good for digging burrows — though they often take up residence in a hole abandoned by something else.

In today’s world, however, the toad’s reproductive habits are getting it into trouble. The muddy pools they seek often form along dirt roads or trails,  exposing tadpoles to crushing tires and feet of all descriptions.

That, plus habitat loss, is why the toads are in decline in Southern California.

The pools have two purposes. One is pure science: to learn whether pools of varying shape and size will hold water in Orange County’s scrubland. The second is to try to provide badly needed habitat for the toads.

The scientists dug out the holes over the summer, as the spadefoots, which grow to 1 .5 to 2.5 inches long, slumbered in their burrows, awaiting winter and spring rains.

“When the rains come is not that predictable,” said Adam Backlin, an ecologist with the U.S. Geological Survey. “We wanted the pools in place before the rains came.”

The toads’ summer ’sleep’ is known as estivation, the seasonal equivalent of wintertime hibernation. When awakened by rains, the toads emerge to breed and lay eggs.

The pools must last at least 30 days — enough time for the tadpoles to mature into toadlets and hop away to find their burrows.

 ”They’re really only active during rainy times of year,” Backlin said. “In Southern California, that’s not very often.”

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(Photos of spadefoot toad and of scientists digging pools courtesy Wida Karim, Irvine Ranch Conservancy.)

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