By Biologist Wade Nolan
I was walking into the wind, north of Wide Bay Alaska, when my feeble nose picked up the smell of something big and dead. On the Alaska Peninsula, this almost always means you have found a bear kill. Plan A was not to surprise a giant brown bear as he guards his fermenting dinner. We got out the binoculars and spotted an area about the size of a modest back yard that had been churned up by what looked like a small dozer. In the center of this excavation there was what we bear folks call a “bear pile.” A brown bear had killed and buried a moose above ground. Almost always the bear is handy, so we circled up wind and blew the bear out of the nearby alders where he was sleeping it off. He stayed in heavy cover for a long while and departed, at least for now. We had to get a closer look.
Yep, it was a mature moose – one leg hung out of the mound complete with a coffee-can sized hoof. The top of the pile was compressed as the owner had recently been lying on top to ward off predators and scavengers. It is not at all unusual to find such a “bear pile” in the spring. Both the resident Alaska-Yukon moose and the caribou are in their most stressed time of the year. Winter is tough on these ungulates, and just before green-up is the worst. Add hungry brown bears to the mix, and it’s a bad time to be a moose or caribou. But they have got to eat too. What do they eat and how much? Biologists have been speculating this question for a long time and thanks to some modern science, they are getting answers.
Bruce Dale is the Wildlife Science Coordinator with the state of Alaska, and he teamed up with another biologist out of Palmer, Alaska, Chris Brockman. Together they planned to break some new ground in brown bear research. Their plan was to attach cameras/GPS collars to brown bears and have them shoot selfies to help unravel the bear predation question. I spoke with Chris Brockman to help me understand his research.
They chose to work out of an area that is quite accessible and only about 50 miles from Glennallen, Alaska in the Nelchina River drainage. I know a lot of people who live in this region, and I’m familiar with the wilderness in this vast drainage. Snowcapped mountains tower to the south and catch much of the snow that comes off the Gulf of Alaska. Most of the trees are black spruce with a few white spruces in the dryer places. Along the vast river and creek bottoms, willow and cottonwood thrive. Willow is the staple of moose. On the higher elevations, dwarf birch, ankle high blueberry bushes and dwarf willow carpet the rolling hills. The pastel green ground cover is caribou moss, a staple lichen of caribou. In short, it looks like much of Alaska. One more thing, the Nelchina Basin is a deep freezer in winter with 40-below being common.
The earlier research was limited to twice-daily airborne observation, which at best got a short glimpse of bears and their prey. Not only was it difficult to see the bears if they were in heavy cover, but also identifying the prey species was complicated. With this new methodology, they may just get a glimpse of what was happening on a minute-by-minute basis. Here is their research model. They captured and collared 17 bears from 2011 – 2013. Among all the animals you can attach a collar to, bears may be the most likely ones to get rid of the collar. That’s was exactly what happened, and only seven bears supported video collars for the entire data set. The good news is that those seven bears gathered over 36,376 video clips across a period of time when bears are most likely to be feeding on moose and caribou calves. The cameras took a 10-second video clip every 15 minutes from mid-May to the end of June, which is calving season. At the end of the study, bears were re-darted and camera collars collected.
What they learned was remarkable. Video camera footage of these seven brown bears showed that they killed approximately 238 moose and caribou calves across the 45 days. That’s an average of about 34 moose and caribou calves per bear, of which 13 were moose. Note that 75% of the Nelchina caribou herd’s calving area is within the study area. Because moose numbers in the Nelchina Basin dwarf the number of caribou means that brown bears are having an impact on moose calf survival. Don’t forget that bears are not the only predator working on moose calves. Wolf packs and natural calamities also play a major role, although wolves have been intensely managed in the drainage. Also, don’t forget that not all the bears in the Nelchina drainage supported a video camera, most didn’t. It is tough being a moose calf in Alaska.
The research could divide out the daily structure of an average camera equipped bear. It revealed that a brown bear in this study spent on average 60% of his day bedded or resting, 21% of the day traveling, 6 % of his day just standing around, and 6% of his day feeding. Here is the interesting statistic. These bears spent just 1% of their day hunting. Although calves made up most of their red-blooded prey, these bears also ate Trumpeter swans, snowshoe hares and in one case a ten-year-old male brown bear killed and ate a six-year-old sow.
I personally have spent a lot of time observing moose calf predation in Denali National Park. Across a six-year period, I was privileged to accompany wildlife biologist Vic Van Ballenburghe as he researched Alaska-Yukon moose. Vic is one of the top moose biologists in the world. One spring we tried to get footage of bear-based moose calf predation across the calving period. Although we observed a couple of feeding sequences, we never actually observed the kill. One afternoon, I was alerted to a situation at mile nine of the park road where a single wolf had taken down two moose calves while the cow moose tried to protect them. She spent the next 20 hours trying to protect the dead calf bodies as the wolf slowly outsmarted her. A wolf weighs 150 lbs. and is not equal to the predatory prowess of a brown bear.
As years spun forward Vic realized that many of these Toklat grizzlies were becoming better and better at targeting moose calves until one year he told me that he estimated that there might have been no moose calf survival in some regions of the park. How could that be? Here is the likely answer. Bears have a home range and they know where seasonal abundances of food lie. For example, they arrive at salmon streams each year just as the salmon run arrives. In the case of moose, they first discover the area where a mature cow moose chooses to have her calves and the bear enjoys a successful hunt. Unable to reason, that moose returns the next year to the same area to calve. This area may be under an acre in size. Likewise, the bear arrives the same time the following year and teaches her cubs that this is a hot spot for moose meat. The cubs now know the spot and the moose’s chance of successfully raising a calf diminishes. The successful cows switch calving areas.
All this data and observation is part of a scientific management plan that the Alaska Department of Fish and Game uses to set methods and bag limits for species they are managing. Allowing hunting brown bears/grizzlies over bait was added to their management strategy in many game management units. Better science, like GPS collars equipped with cameras, help them do their job.
To view a videos from the study click here
These clips are from a collar camera on a 10-year-old, 700-pound male Alaska brown (grizzly) bear.Clip #1 is a composite of four separate clips; it shows a few seconds of the bear eating, then it jumps to a clip of the bear rushing through brush at a moose calf and grabbing it. He’s feeding again, then another scene of the bear rushing at prey. In clip#2, he’s feeding on a bear he killed.
