A grizzly bear that fatally mauled a hiker in Yellowstone National Park was killed after DNA evidence linked the animal to the scene of a second hiker's death a month later, a park official said Monday. 
 
 The decision to euthanize the 250-pound (113-kilogram) female bear was meant to protect park visitors and staff, Superintendent Dan Wenk said. 
 
 However, the investigation remains open, and officials might never know definitively whether the same bear that killed California hiker Brian Matayoshi on July 7 also took the life of John Wallace of Michigan in August. 
 
 Evidence showed multiple bears, including the sow, were near Wallace's body but not if the sow made any contact with Wallace. The bear was allowed to remain free after Matayoshi's death because park officials said it was reacting naturally to defend its two cubs. 
 
 "We made a decision at that time, based on all the information available, that we did not have a bear with a history or a bear that was demonstrating any predatory nature," park spokesman Al Nash said. 
 
 The deaths of Matayoshi and Wallace were the first blamed on a bear inside the park in a quarter-century. Two fatal maulings occurred just outside the park in 2010. 
 
 There were no witnesses to Wallace's killing. He was hiking alone in Yellowstone's Hayden Valley, about eight miles (13 kilometers) from where Matayoshi was killed. The mauling occurred in a backcountry area frequented by bears, and signs posted at trailheads warned visitors to take precautions. 
 
 By the time Wallace was found by other hikers a day after the mauling, one or more bears had fed upon his body, Nash said. Authorities couldn't determine from the evidence whether the sow bear "attacked Mr. Wallace or came upon the scene subsequent to the attack, but we certainly know the bear was at the scene," he said. 
 
 The sow bear was linked to the scene through DNA analysis of hair and scat samples found near Wallace's body, Nash said. 
 
 The two cubs were captured and relocated to the Grizzly and Wolf Discovery Center in West Yellowstone. 
 
 In the aftermath of Wallace's death, park officials said they did not believe the responsible grizzly was the same one that had killed Matayoshi because they found no cub tracks at the scene. Investigators now believe those tracks might have washed away in a rain storm that went through the area before Wallace's body was discovered. 
 
 Chris Servheen, a grizzly bear recovery coordinator with the U.S. Fish and Wildlife Service, said investigators have concluded the sow bear was at the scene for some time. He said details would be released when investigators complete their report into the attack, which is expected to take another month. 
 
 Servheen also said park officials had made the best decision they could after Matayoshi's death, given the circumstances. 
 
 Since the mauling, park officials have captured at least seven bears in the Hayden Valley. DNA, tracks and other evidence from the scene showed at least nine bears were present around the general time of Wallace's death, drawn by two nearby bison carcasses. 
 
 All of the captured bears were radio collared and released. 
 
 An estimated 600 grizzlies live in the greater Yellowstone area, which includes parts of Wyoming, Montana and Wyoming. A recent report showed run-ins between humans and that growing bear population reached record levels last year, with 295 conflicts recorded by researchers. 
 
 Three of every four of those involved bears killing livestock or damaging property to get food, garbage, livestock feed or other human-related foods. Nine human injuries were reported in 2010 _ almost double the long-term average of five a year. ||||| (CNN) Yellowstone grizzly bears are emerging from their winter hibernation to news that wildlife officials no longer consider them threatened. 
 
 "Stable population numbers for grizzlies for more than a decade also indicate that the Yellowstone ecosystem is at or near its carrying capacity for the bears," it said. 
 
 Hottle also loves visiting Glacier National Park in Montana, a nine-hour drive by car. "There's a wildness about Glacier that makes it even more dangerous and adventurous than Yellowstone," he said. Glacier's Wild Goose Island is shown here. 
 
 Glacier National Park – Hottle also loves visiting Glacier National Park in Montana, a nine-hour drive by car. "There's a wildness about Glacier that makes it even more dangerous and adventurous than Yellowstone," he said. Glacier's Wild Goose Island is shown here. 
 
 Hottle recommends that hikers travel in groups of at least three, stay on designated trails, carry bear pepper spray and make noise as they hike to avoid surprising bears (mother bears can attack when surprised). He and his family have hiked "every inch" of Electric Peak, a nearly 11,000-foot mountain. 
 
 Yellowstone: Our first national park – Hottle recommends that hikers travel in groups of at least three, stay on designated trails, carry bear pepper spray and make noise as they hike to avoid surprising bears (mother bears can attack when surprised). He and his family have hiked "every inch" of Electric Peak, a nearly 11,000-foot mountain. 
 
 In elk mating season, which starts around September, the bulls come down from the mountains and gather up as many cows (female elk) as they can into harems. Shown here is a harem of 27 cows resting in Mammoth Hot Springs near the town post office. Visitors are cautioned to stay at least 25 yards away from the elk, which have been known to ram cars and trap people. 
 
 Yellowstone: Our first national park – In elk mating season, which starts around September, the bulls come down from the mountains and gather up as many cows (female elk) as they can into harems. Shown here is a harem of 27 cows resting in Mammoth Hot Springs near the town post office. Visitors are cautioned to stay at least 25 yards away from the elk, which have been known to ram cars and trap people. 
 
 Rangers plead with with visitors to pull off the road to shoot pictures of bison (shown here in the Lamar Valley) or other wildlife that call Yellowstone home. Travelers have been known to stop their cars in the middle of the road to look at the view, or worse: look sideways to admire the nature while driving. 
 
 Yellowstone: Our first national park – Rangers plead with with visitors to pull off the road to shoot pictures of bison (shown here in the Lamar Valley) or other wildlife that call Yellowstone home. Travelers have been known to stop their cars in the middle of the road to look at the view, or worse: look sideways to admire the nature while driving. 
 
 There's a good chance of spotting wolves on the drive to the Lamar Valley, Hottle says. He likes to stop at a pullout about halfway to the valley and hike into the woods, where he can sometimes see a wolf or its pack. (Hottle found this wolf in his backyard.) 
 
 Yellowstone: Our first national park – There's a good chance of spotting wolves on the drive to the Lamar Valley, Hottle says. He likes to stop at a pullout about halfway to the valley and hike into the woods, where he can sometimes see a wolf or its pack. (Hottle found this wolf in his backyard.) 
 
 Grand Prismatic Spring is Hottle's favorite spring in the park, and it's in Midway Geyser Basin about five miles from Old Faithful. When the light is right, hike up one of the mountains surrounding the spring and you'll see the steam change colors because of the spring's bacteria. 
 
 Yellowstone: Our first national park – Grand Prismatic Spring is Hottle's favorite spring in the park, and it's in Midway Geyser Basin about five miles from Old Faithful. When the light is right, hike up one of the mountains surrounding the spring and you'll see the steam change colors because of the spring's bacteria. 
 
 Castle Geyster just in the same basin as Old Faithful. 
 
 Castle Geyser – Castle Geyster just in the same basin as Old Faithful. 
 
 Old Faithful Geyser may be the most-famous "resident" of Yellowstone National Park, but park ranger Dan Hottle says there is much more to see at the 2.2 million-acre park. 
 
 Yellowstone: Our first national park – Old Faithful Geyser may be the most-famous "resident" of Yellowstone National Park, but park ranger Dan Hottle says there is much more to see at the 2.2 million-acre park. 
 
 "In response to the successful recovery of one of the nation's most iconic animals, the U.S. Fish and Wildlife Service today proposed to remove the grizzly bear in the Greater Yellowstone Ecosystem from the Federal Lists of Endangered and Threatened Wildlife ," it said. 
 
 Delisting means the bears are no longer threatened, and would not be protected by the Endangered Species Act. They could be hunted within the Greater Yellowstone Ecosystem, which lies in Wyoming, Idaho and Montana , though not the Yellowstone National Park itself. 
 
 Conservation plans 
 
 The wildlife service said the restoration of bear populations in Montana, Wyoming and Idaho "stands as one of America's great conservation successes." 
 
 "Our proposal today underscores and celebrates more than 30 years of collaboration with our trusted federal, state and tribal partners to address the unique habitat challenges of grizzlies," director Dan Ashe said. 
 
 "The final post-delisting management plans by these partners will ensure healthy grizzly populations persist across the Yellowstone ecosystem long into the future." 
 
 Public chance to comment 
 
 The wildlife service is seeking comment from the public, agencies and scientists after publication in the Federal Register, expected in the next few days. 
 
 "Even with this proposed delisting, the service remains committed to the conservation of the Yellowstone grizzly bear, and will stay engaged to ensure that this incredible species remains recovered," Ashe said. 
 
 Still in need of protection? 
 
 "Yellowstone grizzly bears are an isolated population that is experiencing high levels of conflicts with people and is likely declining in the wake of the loss of whitebark pine, a critically important food source," said Sylvia Fallon , a senior scientist at NRDC. 
 
 Fallon questioned the accuracy of the population estimates, saying the bears were on the decline. 
 
 She added they would likely also need to be connected to bears outside the Greater Yellowstone Ecosystem to avoid genetic problems. 
 
 "The Endangered Species Act has been tremendously successful at saving this population and preventing its demise," she said. 
 
 " And retaining those valuable protections until the Yellowstone grizzly population is more robust and its future more certain is the best way to turn that past success into true recovery." 
 
 The Fish and Wildlife Service removed the Yellowstone grizzly bear population from the threatened species list in 2007, but the decision was challenged and later overturned by a federal district judge. A later appeal by the service failed. 
 
 The wildlife service describes endangered species a s those at the brink of extinction now while a threatened species "are likely to be at the brink in the near future." 
 
 Awake and hungry 
 
 Meanwhile, Yellowstone National Park has warned that its grizzlies are awake, hungry and looking for food. 
 
 The National Parks Service said the first confirmed report of grizzly bear activity after the winter hibernation came nearly two weeks ago. 
 
 1st grizzly sighting of the spring today over Nez Perce Crk. Get a bear safety refresher at https://t.co/PsyfFoKaT9. pic.twitter.com/JhkflMRwOY — YellowstoneNPS (@YellowstoneNPS) 24 February 2016 
 
 "Bears begin looking for food soon after they emerge from their dens," the parks service said in a statement. 
 
 It recommended that park visitors stay in groups of at least three, make noise on the trail and carry bear spray. 
 
 "Yellowstone regulations require visitors to stay 100 yards from black and grizzly bears at all times. 
 
 The best defense is to stay a safe distance from bears and use binoculars, a telescope or telephoto lens to get a closer look," the parks service said. 
 
 Yellowstone closes areas of the park where humans are more likely to encounter bears that could react aggressively while feeding on elk and bison carcasses.
– A mama grizzly linked to the mauling death of two hikers in Yellowstone Park has been killed by rangers. Two men were mauled to death in separate incidents over the summer in the first bear killings in Yellowstone in a quarter of a century. Bear DNA found at the site of the first mauling was also found at the site of the second death a month later. In the first attack, a grizzly sow with two cubs chased and killed a man as he hiked with his wife. A report by Yellowstone rangers concluded that a possible "contributing factor" to the mauling was that the couple "ran from the bear while screaming and yelling," and they decided not to track down the grizzly. "We made a decision at that time, based on all the information available, that we did not have a bear with a history or a bear that was demonstrating any predatory nature," a park spokesman told the AP. But the same sow's DNA was found at the site of the second killing of a hiker walking alone—although tracks and DNA from several other bears were also found at the body, and rangers can't be certain which animal killed the hiker. The euthanized grizzly's two cubs were captured and relocated to the Grizzly and Wolf Discovery Center wildlife park in West Yellowstone. An estimated 600 grizzlies live in the greater Yellowstone area.