This was written for a magazine that requested I write a bear biology article for them. When I sent them this they liked it but wanted me to remove the section about the controversies of controlled burning. I refused and they decided not to publish it. I was pretty disappointed since it's the major issue facing the conservation of black bears in the SW US, but I hope many enjoy reading it here. As always, thanks for looking.
It was mid April when the sow awoke for the 4th time since October. The sounds coming from the 3 cubs suckling eased her instinctive caution. She inspected her den, the nest of dead leaves, shredded agave and yucca was still dry. Although she had not defecated or urinated since October, the 3 month old cubs had. She ingested the small amount of cub feces and looked outside, alert for danger. Having smelled none she rolled so the cubs could easily find her nipples. The cubs were getting larger each day, their eyes had been open for a month and their claws allowed them to climb almost anywhere. Although she could move quickly, a protein in her circulatory system caused strong fatigue. After a short wakening she would again be in an almost comatose sleep known as torpor. Her heartbeat dropped from 40 to 10 bpm, her metabolism slowed 50 %, but her body temperature remained the same. Because the cubs were growing fast, she had to manufacture more of the richest milk (20 -25% fat) known among terrestrial mammals. Three cubs is rare in AZ and cost her over a pound of fat daily; each required up to 30 oz of milk per day.
Although she had moved little over the past 6 months, her muscles and bones remained strong as waste products from fat metabolism rebuilt them. Evolution had formed an animal that could “ignore” a 6 month period of starvation by shutting down. Finding and duplicating the torpor causing protein called Hibernation Induction Trigger (HIT) was a high priority for biologists as it could mean extending the life of transplanted organs by 300%. Discovering how waste products recycled to rebuild muscle and bone could save humans suffering while bedridden. That meant nothing to the sow. Evolution had also created an animal that thought only of self preservation, feeding, and protecting her offspring; also an excellent adaptation. Too much thinking is dangerous in a world that moves fast.
In another month she was finally awake, although groggy and slept often. Her cubs were persistent with suckling and playing, sometimes chewing a little too hard on mom’s ear. The den was home until mid June. It was located on a north facing canyon slope and not much more than a short 2 foot by 12 inch diameter tunnel opening into a small compartment. A large boulder over the hole kept moisture out and provided afternoon shade. The den was surrounded by dense brush and 2 large alligator junipers. The junipers provided berries, some of sows first foods. She had lost 70 lbs the last 6 months. Her first forays were close and the cubs remained in the den. Since she had not eaten or drank since last October she headed to the canyon bottom to feed on sprouting grasses and drink from a stream. Her hunger was strong but the instinct to protect her cubs was stronger so she didn't travel far enough to eat as much as needed. For a week she made multiple trips alone, but soon the cubs followed and she fed longer. She preferred patches of juniper berries, old acorns or manzanita berries but they were rare and she predominantly ate grass. Although grass was plentiful, its nutrition was limited. Bears don’t have the advanced digestive system of deer, and she ate over 8 pounds a day just to not lose weight. Gaining the 70 pounds back would have to wait until mast (berries and nuts) became ripe. The cubs imitated mom and grazed, but it was mom’s milk that gave them energy for growth and stamina. They returned to the den to sleep until Mid June.
When they left the den permanently the sow’s nose was high in the air during this dangerous period. Males (boars) were moving now, up to 20 miles a day looking for females ready to mate. She was lactating and would not go into estrus, but that would not stop a male from investigating her. Males know if they kill the cubs and the female stops nursing, she could come into estrus within 36 hours. If he killed the cubs and stayed around he would father a litter; it had happened to the sow before. Therefore the sow preferred areas of thick brush with tall trees but with less food. Tall trees were essential as the cubs could now climb an 80 foot conifer. Males could climb but not as high where the trunk was narrow and limber. Each day after feeding the sow dug a flat bed with loose soil near the base of a large tree surrounded by dense brush for the 4 of them to lie.
Where the sow travelled was similar to the area she learned from her mother. Sows often adopt part of their mom’s home range, and her range extended just east of the area she had grown up in. The 3 cubs, one black and 2 brown, followed their cinnamon red mom over the same area that she led her last 2 litters. Only now the sow was having a difficult time finding tall trees. Four years ago a catastrophic fire had burned part of her home range, killing tall trees. The shrubs were coming back, there was plenty of grass and burnt trees harbored insects, but the lack of trees concerned her. She would have liked to avoid the area but the need for food and the fear of searching new areas forced her to remain. That the area was supposed to have been treated with a controlled burn before the fire was unknown to her, as was the politics and financial cuts that prevented the controlled burn that might have saved the large trees in a wildfire. Concerns over EPA air restrictions, paper work to burn in an area near spotted owls, and lack of money for the fire crew were beyond her. Unknown to the sow, this unfortunately was occurring throughout the SW as drought, warming trends, and lack of prescribed burns increased the number of catastrophic burns in black bear habitat. The sow continued her vigilance but she was still hungry, and the burned area still had the most grass and insects available, berries were not ripe yet.
Toward the end of June the four were in the burn when the sow smelled another bear, close! She woofed for the cubs to scramble and turned to meet the oncoming bear. A large boar met the sows advance but immediately bounced around her. The female followed but the male was faster and soon both he and all cubs were gone in the brush. She followed calling to the cubs. Two came to her and she had to lead them to a tree almost a quarter mile away. After they climbed she went back for her missing cub, still cautious of the male. Her calls continued over 2 hours when she finally got a scent and bounded to its source. All she found was the skin of the brown cub. The male had killed the cub, then noting the female had left, ate it to replenish his own hunger. The mother nosed the skin as if to wake it and then lay down next to it but after 5 minutes was back to the tree where she collected her remaining cubs. They left the burn into an area of thicker cover, the 2 cubs playing chase and occasionally bounding off their mothers back. Any observer would have not have noted anything unusual had happened. The sow kept her cubs in deep brush for 2 days until hunger forced them back to grazing areas.
Life was easier in mid July. Manzanita, chokecherry, and squawberry all ripened and ant nests reached peak populations. This allowed the trio to stay in thick cover and the berries allowed the sow, now 125 lbs, to begin putting on weight. Not only was there more food, but the cubs were able to digest berries easier than grass and their demand for milk decreased. The cubs continued to play with one another, and sometimes got Mom involved. She concentrated more on feeding since boars were moving less and she avoided the burned area.
The sow and her family lived on one of the many ‘sky islands’ found in Arizona, a mountain range that rises straight up from valley floors and is surrounded by a "sea of desert". The elevation range results in different temperatures, influencing precipitation and resulting in a wide variety of plants in close proximity. If there was not ripe food at one elevation, there probably was at another elevation allowing for some of the highest bear densities in the western United States. For the remainder of the summer this was what the trio did, moving up or down depending on where the sow’s memory and smell determined there might be food.
One day in late July the sow noticed a young Coues’ whitetail fawn that unknowingly walked within 15 yards of the sow’s bed. In the back of the sow’s mind the instinct to attack the fawn occurred. Black bears throughout North America, particularly Alaska, areas of the Rocky Mountains, and along the east coast frequently attack and eat large mammals. Occasionally it happens in AZ, but as with this sow, the majority of AZ’s black bears ignore larger more nutritious protein. The sow was beginning to gain weight quickly now so she let the fawn go. Neither the sow, nor the biologist that study them, understand why bears in the SW seem to be strictly herbivores when protein is available.
By mid August, 3 of the local 6 species of oaks were producing acorns. Acorns are primarily carbohydrates and the reason bears do well in the SW, particularly on sky islands. A bear in the White Mountains might have to walk 20 miles to get to this rich food source, whereas a sky island bear can go 500 to 1000 feet up or down. After finding a thick canyon overgrown with oaks, the three would not move more than 500 yards in any direction for the next 5 weeks. She ate up to 5 lbs of acorns daily and gained over a pound each day. Valuable fat reserves were now just as important for the cubs. Nursing had decreased and would stop during the upcoming winter.
One evening in mid September the sow took the 2 cubs down slope over 2000 feet into the Sonoran desert, a place the cubs had yet to visit. They would spend the next 3 days bedded in thick chaparral during day, but in early morning and evening twilight they gorged on the red ripe fruit of prickly pear cactus. The sugar in the fruit attracted the bears, and the increased blood insulin increased the amount of glucose stored as fat.
Unknown to the bears; they were being watched through matching sets of 10 x 50 binoculars mounted on tripods. The couple had scouted this area the weekend before and was excited to spend opening day of bear season watching canyon slopes littered with prickly pear. As night became day, the young lady spotted the movement of reddish brown first. She jabbed her husband, pointed, and whispered bear. As she reached for her rifle her heart sank when her husband whispered “Cubs, two of them”. It was illegal and unethical to shoot a mother leaving 2 cubs to die. The hunters sat sullenly for just a moment, but started enjoying the show as the bear family ate cactus fruits. The hunters felt there was nothing else in the world but them, the bears, and an AZ sunrise and it became a day they would reminisce about for years. That afternoon the sow took her cubs back up the mountain to an area near her previous den. She never heard the gun shot that took a boar in the same canyon by the couple two days later.
The sow found a large boulder in close proximity to thick Manzanita and Juniper and began digging, with rest stops for more gorging of oak and juniper. Within a week the den was finished and all 3 bears began bringing bedding materials as mid October approached. By this time the sow was almost 200 lbs and the cubs were between 50 and 60. The HIT protein began to flow and they spent most of their time in the den as their metabolisms slowed. This was the sow’s 3rd litter of cubs, but the first time 2 had survived. One litter she lost entirely, she managed to enter a den with one of 2 cubs the other time. When she awoke she would drive these 2 away in anticipation of breeding again if age didn't prevent it. But for now, she was only aware of fatigue. Soon all 3 were torpid, and would hardly move over the next 6 months.