In the Sonoma fire zone, Peter Tira returned to his in-laws’ home site in Glen Ellen, where last October every house on the block burned to their foundations.

“I was expecting wholesale devastation, like a nuclear bomb,” said Tira, who works for the California Department of Fish and Wildlife. “The human tragedy is overpowering, the loss of homes, the loss of lives. I went to where the house had been and I couldn’t believe it. Right behind it, what had been the backyard, the garden was intact. I couldn’t believe how good it looked.

“Nearby, I was also surprised how much wildlife habitat was unburned or very lightly burned.”

Amid the personal devastation, Tira said, people have been asking the DFW if wildlife, birds and fish could survive the recent series of cataclysmic wildfires.

The answer, say DFW biologists from past and present, is that wildlife is genetically wired to survive such disasters.

“These native species have evolved from Day 1 with fire as an ever-present part of the landscape,” Patrick Foy, a DFW captain, said. “They have adapted, evolved and are well-equipped and genetically programmed to survive wildfires.”

Roughly 8,000 fires have burned nearly 1 million acres this summer, according to the California Department of Forestry and Fire Protection and the National Interagency Fire Center. Last October, the Tubbs Fire destroyed 5,636 homes and killed 24 people.

Wildlife finds a way

During the 257,000-acre Rim Fire west of Yosemite National Park, I arranged an escort into the fire zone to see if the fire had wiped out the wildlife. Instead, I found a deer feeding on a patch of grass that escaped the flames, squirrels and songbirds in an unburned swath near Cherry Lake, and an osprey diving at the lake to feed on a trout.

Nearby, I learned that deer and other wildlife had run off to the greenery and lakes at Pine Mountain Golf Course near Groveland, and other golf courses, as well as the athletic fields at schools in the region. In other words, they found a way out until the land could be reborn.

“Even in intense wildfires, they have avenues of escape,” Tira said. “There’s a sliver of green, a pond, lake or river, and they find it. We’re pretty confident were not going to be seeing wholesale widespread wildlife losses.”

Foy confirmed that and added, “Every single day, they survive for a living and they are better at it than most of us.”

The late Brian Hunter, a wildlife biologist and retired regional manager for the Department of Fish and Game, once took me aside and explained how to assess the difference between “a disaster” and what he called “a bad thing that happened.”

“A disaster,” said Hunter, who died last October, “is when you lose your home.” Then he paused for effect: “A disaster for wildlife is when its habitat is destroyed, like when wetlands are paved over to build a shopping center. The habitat is lost forever. There is no coming back from that.

“For fish and wildlife, a fire, an oil spill, things like that, these are bad things that happened. It looks bad right now, but the habitat isn’t lost forever. If the habitat isn’t lost, then it can come back, and so will the wildlife.”

Case-by-case

Tira, Foy and other DFW wildlife experts explained how many major species survive wildfires.

Deer: “When there’s a fire and they smell the smoke, they are much like people, and they look to get out of there,” Foy said. “They do a very good job of getting out of danger. There can be a loss when things go terribly wrong, but often they can outrun the fire.” One GPS migration study by DFW wildlife biologist Rich Callas found that herds can migrate as much as 40 miles, in a sustained march, often in two or three days. That ability can get them to safe zones. Tira noted that fires are uneven, burning at different heats and patterns, and that leaves escape routes for deer. A word of caution: In Sonoma and other regions with vineyards, Hunter warned about deer-proof fencing, which can block escape routes for wildlife, and Tira added that there have been anecdotal reports where mountain lions have trapped and killed deer against vineyard fences.

Bears: The story of a bear cub with burned paws being rescued from the Carr Fire near Whiskeytown Lake made national news. The message from this encounter is that the juveniles are at risk, Foy said. “They do their best, attempting to run away,” Foy said. “Bears can’t sustain for long distances in short time frames, like deer. Three bear cubs we’ve found, where they survived up in lightly burned pockets of forest, they had burned paws.” Wildfire, however, is not a limiting factor to bear populations, Foy said. In the past 40 years, an era during in which wildfires have become bigger, more intense and more common, the bear population in California has expanded from roughly 10,000 to 15,000 in the 1980s, according to DFW estimates, to 25,000 to 30,000 now.

Small animals: Ground squirrels, rabbits, badgers, voles, weasels and many other small wildlife species will dig deep into the ground to survive wildfires. “They already have escape routes from predators,” Tira said. “They use those same routes to get away from fire. The fire will pass right overhead. They can wait it out.” Others, such as mink, beavers and fishers, can survive in watersheds, which often go unburned even in near-incineration events. In the Rim Fire, I found entire slopes of manzanita and chemise that were burned to bare ground, yet nearby, along the Tuolumne River, riparian zones at water’s edge were often untouched. That provided refuges for many small wildlife species.

Birds: “As with people, some individuals get disorientated and can get caught,” Tira said, “but most birds just fly away.” This includes large birds, such as eagles, ospreys and owls, and very small birds, such as the tiny migratory songbirds. In parallel studies, in which both Foy and I took part, we joined wildlife experts who caught tiny migratory songbirds, from warblers to sparrows, in mist nets set in micro-flyways. Some of the birds had bands, which traced their origins to as far away as the Southwest and Mexico. “A bird that migrates from Mexico has the capacity, stamina and motivation to get out of the way of fire,” Foy said. In addition, Tira noted that the migration of birds on the Pacific Flyway, which starts in September with shorebirds, sandhill cranes, and follows with ducks, coots and geese, is not yet under way en masse. Those birds have not been in harm’s way. As they arrive, they can fly to safe havens.

Fish: The sight of helicopters with huge buckets scooping water out of lakes to dump on fires has led some to believe that fish are being picked up and killed. That is not what happens, say the experts. “When the helicopter approaches the lake, if there are any fish, they get scared off by the rotor wash and they are not sticking around,” Foy said. In addition, at Shasta Lake, for instance, where helicopters have been scooping water for weeks, the surface temperature has been 82 degrees. That means most of the fish are submerged in the thermocline, roughly 50-80 feet deep. They will not rise to the surface waters until October, when summer’s layer of warm water on the surface sinks with the arrival of cool weather, and the lake “turns over.” “It’s unlikely there’s any fish in those buckets,” Foy said.

Tom Stienstra is The Chronicle’s outdoor writer. Email: tstienstra@sfchronicle.com Twitter: @StienstraTom or Facebook