None of the three bears Game and Fish employees killed recently had rabies test show, which some officials feared might be the cause of their unusually aggressive behavior.
State authorities are still waiting for DNA results to confirm whether any of the three bears killed by a federal contract hunter were involved in the three attacks on humans some 12 miles northeast of Payson.
Officials believe hunger prompted the bears to go after humans, something they rarely do. Officials have recorded 10 bear attacks in Arizona in the last 22 years — three of those within the past month.
A 19-year drought coupled with low moisture this winter means the bears don’t have enough to eat. The staples of their diet — berries, acorns and tubers — are just not there, said Brian Wakeling, a Game and Fish biologist who has studied black bear behavior.
Recent highway improvements may have also fragmented the black bears’ habitat and made it harder for them to get enough to eat, he said.
Highway 260 went from a small, winding, two-lane roadway last year to a four-lane divided highway. While the highway includes animal underpasses, the bears may not have adapted to the crossings, Wakeling said.
Wakeling said while the highway improvements have notably decreased elk versus vehicle collisions, they may have had unintended consequences for the bears.
In Banff National Park in Alberta, research showed bears took a long time to start using crossings installed in the late 1970s.
“If you put a barrier in place that restricts access to places where it could consume food before, it places a greater challenge for them to get in there and make a living.”
Some bears get desperate and seek out new food sources and stumble on human habitats, where food is often readily available.
In Arizona, Game and Fish has been studying bear movement near the Mogollon Rim and Four Peaks since the early 1980s.
Researchers found bears have a huge home range, with adult males ranging across home territories of roughly 150 square miles.
Many bears live on top of the Rim during the summer months, eating grass, acorns from the Gamble oak and fawns. Later in summer, when the grass cures out, bears start looking for food below the Rim or go farther north toward Flagstaff, Wakeling said.
Officials say they’re not sure how many bears live in Rim Country, but that the population approaches 3,000 statewide.
In the mid 1980s, researchers found four bears living in five square miles in the Four Peaks Wilderness Area.
“That was one of the densest populations in the state,” he said.
On top of the Rim, he said the bear density is probably more like one bear for each five square miles.
Below the Rim, the mix of oaks, junipers, pines and streams offers a greater diversity of food and so supports more black bears, the only bear species in Arizona. Black bears are considered the least aggressive of North America’s bears.
When a male adult bear finds an area with a good food supply, he tends to dominate and protect it.
Male bears will often even kill yearlings who wander onto their turf.
For that reason, cubs stay with their mother for two hibernation cycles, until they are large enough to live on their own.
When female bears leave the den, they are often much smaller than their male counterparts. “Female yearlings are afraid of everything in the woods,” he said. “You almost never see a female yearling go into a campground — they are very shy.”
Male yearlings, on the other hand, need to set up a territory, but find other bears have already laid claim to most of the good territories.
Those males often learn that humans are not around at night, so they start to enter human-occupied areas at that time, feeding on garbage, bird feeders, grills or pet food.
“Quickly, bears become habituated to the presence of humans,” he said. “When they get conditioned to the presence of humans and they know that if a person is around they will get a reward for that, then they are dangerous.”
The bears killed by Game and Fish recently include two young males and an adult female, who did not show signs of having had cubs this spring.
Bears that become accustomed to and unafraid of traffic, noise and human activity cause more conflicts with humans, especially if they have come to associate people with food.
“The latest attack victim appeared to take the appropriate precautions, but this bear had already become used to people and expected to find a food source in human-occupied areas,” he said.
Wakeling said any bear that shows aggression toward a human has to be killed.