Sunriver to aid toads’ annual pilgrimage across the street
By Rachael Scarborough King / The Bulletin
Published: July 14. 2007 5:00AM PST
SUNRIVER — The rock on the western bank of Sunriver’s Aspen Lake was disintegrating. In every direction, little brown blobs flew into the air and landed in the grass at the water’s edge.
But the brown mass on the shore wasn’t a rock. It was a pile of 3-month-old Western toads, just emerging from the lake to start their annual migration into nearby forests and meadows.
Every year, adult Western toads lay their eggs in Aspen Lake, and a few months later, the toadlets emerge from the water. This year, however, researchers say they are seeing huge numbers of toads at Sunriver — probably the most in 14 years.
And as the thousands of toads start heading up from the bank and across nearby roads to reach dry land, researchers at Sunriver Nature Center & Observatory are hoping to avoid lines of squished animals. They are planning to move the toadlets across obstacles in buckets, and are asking for volunteers to help.
“If they want to disperse more so they have less competition for food, they’re going to find our parking lot (and) then the roads, so the goal is with the human-made hazards to try to get them past the hazards,” said Sue Manley-Hinton, a naturalist and manager at the Nature Center.
Staffers also are planning to use a leaf blower on the pavement in the Nature Center’s parking lot to encourage the toads to avoid the area, according to a news release from the center.
The toadlets probably will do most of their migrating during the cooler hours at night and early in the morning, Manley-Hinton said. These toadlets are young Western toads that have gone through their metamorphoses — changing from tadpoles to an animal with four legs and no tails — and are about 3/4 inch to 1 inch in length. Full-grown Western toads are about 3 to 4 inches long, Manley-Hinton said.
The toads will spend most of their adult lives out of the water, returning to ponds — possibly Aspen Lake — to breed in about four years, she said.
“That’s the difference between frogs and toads — frogs will spend their whole lives in water, versus toads (that) will live in dryer climates,” she said.
Jay Bowerman, the Nature Center’s principal researcher, said in recent years the lake has usually played host to tens of thousands of toads. This year, researchers think there could be hundreds of thousands getting ready to migrate. In the past, Bowerman said the toad migration has lasted for a few weeks.
“We won’t know now until this migration is finished whether we’ve got a couple hundred of thousand of toadlets that are spread out along a large area of shoreline, or whether we’ve got 10 times that many,” Bowerman said.
In 1993, he added, between 500,000 and 1 million toadlets emerged from the lake. A few decades ago, 1 million to 2 million animals was an average number, he said.
But officials at the Nature Center are still at a loss to explain why this year has turned up such a bumper crop.
“The proximate reason is that there were more adults that laid eggs, but why we had a really good breeding year this year is a surprise to me because I would have predicted it would have been a very low year this year,” Bowerman said. “We did not have particularly good winter conditions. We had three really cold spells, and we did not have much in the way of snow cover to provide insulation. … That plus we had very dry conditions during April and early May when they make their way to the lake to lay their eggs.”
Manley-Hinton said they currently have several theories about the surge. One possibility is that staffers dug out some of the shoreline vegetation earlier this year, which may have made the lake more appealing to the breeding toads.
“Those are sometimes the mysteries that we just formulate questions (for),” she said. “There’s so many variables — was it the temperature? Was it the number of adults migrating here to do the breeding? We sometimes just have to observe, ask questions and look and see if we can pinpoint any variable.”
Western toads are prevalent throughout the Western United States, Bowerman said, and also are known as boreal toads.
This week, signs at the Nature Center advised visitors about the toads, and many people taking a walk along the lake stopped to gawk at the animals hopping across their paths.
Cynthia Fox, who was visiting from Portland with her daughter and son, said they have visited the Nature Center several times in the past.
“It’s amazing,” she said. “Is that cool or what?”
Her 7-year-old son, Michael Malone, pointed out several toads as they hopped along the path.
“Wow, look at them all,” Michael said. “They look like little tiny ninjas, kind of.”