Bear Hibernation Part II

While I was working on black bears in the Yaak for my Masters degree, I had the pleasure of cooperating with Dr. Ralph Nelson from the Mayo Clinic in Rochester, Minnesota. Dr. Nelson was studying hibernation in bears for a variety of human-related reasons, not the least of which was to assist NASA with sending man to Mars. The theory was that if we could induce hibernation in people, we could therefore select astronauts that were somewhat rotund and put them to sleep for 6 months while we sent them off through space. Not only would this alleviate long periods of boredom, but it would also greatly reduce the amount of necessary resources such as food and fuel.

Dr. Nelson had several black bears in captivity in Minnesota that he was studying and from which he collected blood and urine samples. He wanted to know if various parameters such as proteins and hormone levels were similar in wild bears. Dr. Nelson and one of his assistants joined me in the Yaak in March of 1988, where we entered the dens of a number of radio-collared bears that I was monitoring. We took snowmobiles to wherever the bears were denning, tranquilized them, and drew blood and urine samples for later analysis. To my knowledge, researchers have yet to identify what exactly triggers hibernation, but they have found a number of things that can be hugely beneficial for people.

For one thing, bears are able to recycle their nitrogenous waste (urea) and reconvert it back into protein, or muscle mass. Bears have microbes in their gut that converts urea into a form of nitrogen they can use to make new amino acids, which are the building blocks of protein. Imagine doing nothing for 5 or 6 months and you still have the same amount of muscle as before!  This has huge implications for patients on dialysis, whose kidneys are failing and must have their blood cleansed (nitrogen removed) by a machine.

Another thing they discovered is that bears do not experience osteoporosis, or weakening of the bones. Again, if you or I were bedridden for a couple of months, our bones would begin to weaken due to a loss of calcium. This is also a problem with space travel where astronauts do not put pressure on their bones due to a lack of gravity. Researchers have discovered that calcium lost from the bones of bears during hibernation is recycled and re-deposited, resulting in no net loss or strength!

In order for bears to successfully hibernate and reproduce, they must put on very large stores of fat, which are then lost. This process is repeated yearly. Obese people with excess fat often exhibit problems with diabetes and heart disease. Again, bears exhibit no such issues. For patients exhibiting problems with gall stones, scientists have isolated a compound called Ursodiol, which is found in bear bile and is produced by the gall bladder. This compound has since been reproduced synthetically and is currently used by doctors to dissolve cholesterol-laden gall stones and to treat certain liver diseases.

As time goes on, it is likely even more fascinating aspects of bear physiology will be discovered. It will be interesting to see what’s next!


Bear Hibernation (Part I)

People are fascinated by bears for a variety of reasons, not the least of which is their ability to hibernate. Imagine an animal much like people in many ways, being able to crawl into a den for 5-6 months and remain there, without eating, drinking, urinating or defecating, the entire time. As if that wasn’t enough, females give birth to their young in January and nurse and care for them until they eventually leave the den in April or May.

I began working on bears in 1976 in the North Fork of the Flathead under the guidance of Dr. Charles Jonkel and the Border Grizzly Project. In the 1980’s, I did my Master’s Degree on the effects of hunting on black bears in the Yaak. Part of my research involved entering the dens of hibernating black bears, tranquilizing them, and replacing their aging radio collars with fresh ones and gathering biological data. It was an aspect of my life I will never forget.

For starters, when it comes to hibernation, it is important to first understand bear reproduction. Bears exhibit an interesting reproductive strategy called “delayed implantation”. Breeding occurs from late May to early July. The fertilized eggs of a female will cleave several times and form a blastocyst, but unlike most other mammals, the blastocyst remains free-floating rather than implanting in the wall of the uterus and developing further. The blastocysts remain free-floating until the female bear enters the den in the fall, usually late September or early October. At that time, the female bear’s body somehow senses if she has acquired sufficient fat reserves to not only sustain the mother for 6 months, but also allow the young to develop and then nurse them after they are born. If it has been a good year with lots of berries and the female has acquired a thick layer of fat, the blastocysts will then implant in the uterus and development begins. On the other hand, if it has been a poor berry year and an insufficient amount of fat has been accrued to produce and nurse her young while in the den, the blastocysts are simply resorbed by the female or expelled. This unique reproductive mechanism saves the female from wasting a lot of energy needlessly that might also jeopardize her life.

Hibernation itself is a physiological term that involves much more than just sleeping. Breathing and heart rates slow considerably and body temperatures drop 10-12 degrees F. In “true” hibernators like chipmunks and ground squirrels, heart rates may drop to only a few beats per minute and body temperatures may approach freezing. They are very stiff and comatose and unable to defend themselves, if necessary. Also, they must arouse periodically to urinate and defecate. Because the heart rates and body temperatures of bears drop only moderately, many biologists assert that bears are not true hibernators. However, because they can give birth in the den and defend themselves if necessary, all without eating and drinking for 5-6 months, other biologists refer to them as the “ultimate” hibernator!

-Tim Thier

Community, Wildlife

I carry a gun

I carry a gun when I go for walks.  Occasionally I see an article about carrying an everyday pistol – yet these folks might as well be in a different world.  I don’t need the pistol to protect myself – I have two small dogs that are at some level of risk when we run across coyote or cougar.  Come to think of it, the last encounter was when Kiki decided to protect me from 2 grizzlies – they ran for about 80 yards, and then one must have realized that there wasn’t much dignity in 2 grizzlies being chased by a 7-year-old Pomeranian. 

The nice lady who handles problem bears for FWAP explained the advantages of bear spray to me.  I even kind of agree that my aging, overweight Pomeranian has an awesome ability to make a stressful grizzly encounter worse.  That said, bear spray is short range – 7 to 10 yards sticks in my mind.  My little companions can range 50 yards from me, and they have already encountered coyotes, a cougar, and an eagle that regarded them as prey.  I’ve had a wolf kill a fawn within 150 yards of the house.  They’ve all been beyond the range of bear spray, and they have all backed off at my confident approach.  Still, at 71, that confidence is enhanced by the pistol on my hip.

Robert Ruark penned the phrase, “Use enough gun.”  I believe – but it is inconvenient to carry enough gun for a pair of grizzlies everywhere I walk . . . and there are only a few moments of my life spent in grizzly encounters.  Coyotes are more common, as are cats – and over a half-century ago, Paul Totten explained that a 22 is adequate for cougar.  Even a 45 feels small when you’re looking at the real bear, and politely asking, “Please Mr. Bear, you go your way and I’ll go mine.  Neither one of us wants trouble, OK?”  So far the conversation has been effective every time.

So I carry a small, inadequate HK4.  It can protect my small dogs from the common predators, and, if worse comes down to worst, I think I’d feel more competent concentrating on my sights and trigger than praying. 

Community, Wildlife

Game Camera Fails

At 6 am, Mike was out collecting firewood from the stack to start the days fire. Kiki, the older, chubby white Pomeranian was out with him.  Kiki positioned herself off the back steps and started trying to raise the dead with her bark. With enough firewood in hand, Mike called Kiki to the house.  Remarkably, she came when called.  Mike noted that some critter was out there but thought a follow up investigation was better left until daylight.

Later that day, we received a call. “Looks like a grizzly walked down your driveway” the caller reported. We had received 1 ½ inches of snow during the night.  “How’d they know it was a grizzly?” I wondered. Mike replied the prints probably had claws. 

Bear tracks wider than a size 12 insulated boot but not as long as the boot

Wandering down the driveway with the dogs, we found the tracks in the fresh snow.  Holy **** ! That’s a big bear. We followed the tracks up and down the driveway. The bear had lumbered by all 3 game cams.  I pulled the SD cards from the cameras to look for pictures of a big bear.  The Stealth camera did not have pictures of a bear despite the bear slowly walking by the camera. The Stealth camera’s record remained unbroken. (Game Cam 2 link) The Herter’s camera missed the bear.  It had daylight photos of cars and deer but no nighttime photos.  Time to change the batteries.  Only the Cabela’s camera had a not very good picture of the big, fat, healthy grizzly.

The grizzly that left the bear tracks on the driveway at 5:53 am

This grizzly approached the driveway through the woods, lumbered onto the driveway and exited onto Fortine Creek Road before making its way back to the creek bottom. From the time stamp, by the time Kiki was reporting on it at volume the bear was probably on the road.  Our neighbor reported that the bear had been leaving signs in the lower pastures that bordered the creek for several weeks.   Seems we might have a couple more weeks of bears around the place. 

Great pictures of game cameras are frequently a matter of luck.  We have a “good enough” picture to confirm the type and relative size of the bear.  Two of of the cameras completely missed the bear. Even the “best” camera had 1 poor picture but that time stamp sure caught our attention.

Update: A day later with the fresh snow and more reports of tracks, we again went hunting.  This time we found 2 sets of tracks. One large set and a smaller set of tracks that sometimes were adjacent to the larger tracks and sometimes they overlapped the larger tracks. We followed the tracks into the woods to find a deposit from the smaller bear.  Lots of hair in that deposit;  the bears appear to be eating well. Again the bears had walked by 2 game cameras.  Not 1 picture of either bear on any camera.  There are multiple reports of bear tracks in the neighborhood. The bears appear to be making a large loose loop around the Trego school.