Toads hit the road from Northwest Trek

A horde of creatures is on the move at Northwest Trek wildlife park near Eatonville, but animal keepers havent attempted to fence the critters in. Instead, people will try to avoid stepping on them.

The sight of thousands of tiny Western toads carpeting the ground this month as they make their way from wetlands to underbrush amazes even biologists familiar with the seasonal spectacle.

"The whole lawn wiggles, and then they disappear off in the woods somewhere," said Dan Belting, Northwest Treks education curator.

The lawn he's talking about is the backyard of a house that has belonged to Trek since the park added 100 acres to its north border three years ago. Behind the house sits a shallow, man-made pond, off-limits to most Trek visitors. It is one of three places in Pierce County that state Department of Fish and Wildlife biologists list as Western toad breeding sites.

This subspecies, which goes by the scientific name Bufo boreas, was once common throughout the West, but biologists believe populations have declined over the past few decades.

No one has counted the toads throughout Washington. However, biologist Lisa Hallock of the state Department of Natural Resources, who works for the state's natural heritage program, said recently that reports suggest Western toads are disappearing from the Puget Sound lowlands and along the Columbia Gorge, where they were once common.

Because part of Northwest Trek's mission is species conservation, managers were enthusiastic when they discovered the migrating toads in their new backyard. "It's hard to miss," said Belting. Last year, about 10,000 were counted in the exodus.

"There's a time when you can stand here and this whole lawn moves," he said earlier this month. While he talked, he watched dozens of toads scamper around the edge of the pond, apparently waiting for the rest of the crew to mature enough to leave.

The throng is made up of new graduates from the tadpole ranks, each no bigger than a quarter. The rookie landlubbers grew out of thousands of eggs deposited in the pond in the spring.

In general, Western toads do their breeding in shallow water. Females produce between 5,000 and 20,000 eggs, which eventually become tadpoles.

After they lose their gills and tails and grow legs and lungs, the toadlets head for the trees. They don't return to water until they are ready to mate and typically congregate at breeding sites.

Researchers who have tracked Western toads elsewhere found that they travel long distances miles, in some cases but not very fast. It's a lifestyle that puts the toad at odds with people who have drained wetlands, put in roads and built homes, said biologist Marc Hayes, who works for the state Department of Fish and Wildlife.

Biologist Phil Peterson, an Olympia consultant, has studied Western toads for years. "You get a lot of road kill," he said. He recalled one instance along the Nooksack River in Whatcom County when he encountered a migration of thousands.

"You come around the corner and all of a sudden the road is covered with these things," he said.

Migration from ponds, like the one at Trek, is a staged event. Belting said he has watched the toads move as one, out of the wetland, across the lawn and up the driveway that leads from the road to the house.

Where the little toads go after that is a mystery. "Quite honestly, we just don't know," Belting said.

This year Trek managers decided to hire an intern, University of Puget Sound student Keaton Wilson, to help map the migration route and log a timetable.

The direction the toads take could influence plans for wetland restoration and management of the 100-acre parcel, now a buffer between Trek's public areas and Clear Lake, which is surrounded by homes.

Belting said Clear Lake residents have noticed the toads trouping across their properties, but don't know what happens to them after that.

To map the toads' progress, Wilson has erected a series of tiny fences and live traps at intervals surrounding the spot where the toads typically exit the pond.

Hayes, a herpetologist, or specialist in reptiles and amphibians, suggested the fence-and-trap array. The toadlets are too tiny to carry the radio transmitters that are sometimes used to track larger animals. Wilson plans to empty the traps at least once a day.

Wilson's most distant set of fences stands more than 82 feet from the pond. After that, he plans to keep watching. That is, at least until the toads cover a distance about equal to the length of a football field. That's the protocol.

The march usually lasts several days. Whether the migration study continues next year depends on the direction the toads head out, Belting said.

The toadlets are particularly vulnerable at this stage in their development because they aren't mature enough to emit the skin poisons that typically deter predators, Hayes said.

The same kinds of toxins protect toads before metamorphosis, he said. This accounts for their vast numbers in contrast with frogs, most of which are eaten before they grow legs and emerge from the water.

Hallock said scientists suspect the mass migrations of toads may be a ruse to deceive predators.

Jim Lynch, a Fort Lewis biologist who monitors Western toads on the post, said he's noticed the group-oriented behavior even among tadpoles, which tend to swarm. "They really seem to hang out together," he said.

Hallock also noted that small toads often pile on top of each other while basking in the sun.

Once, Lynch said, he encountered a group of 25 toads about one year old near a fallen log. "It was odd. It was interesting," he said. "They were all in the same spot."

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Information from: The News Tribune, http://www.thenewstribune.com