VANCOUVER, Wash. — More than a month after an elaborate multi-agency operation moved some three dozen endangered Columbian white-tailed deer to protected habitat in Clark County, the animals are adapting to their new surroundings.

Now wildlife officials turn their attention to the next phase of the unusual project: keeping track of the deer now at the Ridgefield National Wildlife Refuge. A few of the animals have already wandered outside the refuge boundary at times. Two even swam to Oregon’s Sauvie Island.

“It’s a challenge,” said Ridgefield refuge manager Chris Lapp. “But monitoring is such a huge component.”

The U.S. Fish &Wildlife Service this year moved 37 deer to Ridgefield from the Julia Butler Hansen National Wildlife Refuge, near Cathlamet. Another 12 deer went to Cottonwood Island, on the Columbia River in Cowlitz County. Officials moved quickly to relocate the animals due to the expected failure of a dike separating the Julia Butler Hansen refuge and the Columbia River. If it fails, much of the refuge will flood, putting the animals at risk.

The effort began in January, and continued into April. Workers captured and moved deer with a wide array of tools including nets, tranquilizers, crates, trucks and even a helicopter. Upon their release at Ridgefield, animals emerged inside the cover of a makeshift cloth shelter designed to keep them calm.

Officials originally hoped to move 50 deer. Not surprisingly, the animals were less-than-eager participants in the process.

“We were in a time window that we had to work with,” Lapp said. “We don’t drive it. The animals do.”

As fawning season approaches, managers hope growing numbers will eventually establish three herds of 50 white-tailed deer in the region, which would remove them from endangered status.

So far, the transition hasn’t been entirely smooth. Of the 37 deer plucked from the Julia Butler Hansen refuge and moved to Ridgefield, 10 have died either during or since the relocation. Most were either killed by predators, likely coyotes, or died from the shock of the move itself, Lapp said. Two were struck by cars outside the Ridgefield refuge, said USFWS spokeswoman Megan Nagel.

But those numbers aren’t totally unexpected — the natural mortality rate for Columbian white-tailed deer is about 15 to 20 percent, Nagel said.

“While it’s unfortunate, and we don’t want to lose any deer, we are at the typical mortality rate,” Nagel said.

The relocated have yellow tags on their ears. Radio collars also allow wildlife officials to track the animals remotely. For now, biologists are in the field monitoring and observing the deer three days per week. That will continue in some capacity for at least a year, Lapp said.

As for the deer that stayed behind the Julia Butler Hansen refuge, wildlife managers are working with the U.S. Army Corps of Engineers on a fast-tracked solution to reinforce or back up the failing dike, Lapp said. Construction could start as soon as this year, but likely won’t be done by this winter. Until then, “it’s a race against time,” Lapp said.

“That remaining herd is still at risk because that dike breach is still possible,” he said. “It is something that they’re going to have to monitor very closely.”

At the time the relocation began, there were about 100 white-tails on the Julia Butler Hansen refuge, according to USFWS.

Visitors to the Ridgefield refuge may be lucky enough to spot a white-tailed deer. But don’t count on it — many of the animals reside in parts of the 5,300-acre refuge that are off limits to the public. The landscape offers plenty of ideal habitat, Nagel said. Deer often mingle near forest edges with low shrubs and grass to feed on, she said.

And in a way, the animals returned home with the move.

“One of the reasons we relocated them to Ridgefield is that this is part of their historic range,” Nagel said.