Drivers of Hibernation

Brown and black bears hibernate to avoid winter famine. For five to seven months, they do not eat, drink, urinate, or defecate, a strategy quite unlike other mammalian hibernators. Chipmunks, for example, cache food to eat in between bouts of torpor. Marmots and arctic ground squirrels don’t eat during winter and survive off of their fat stores like bears, but they activate their metabolism periodically to wake and urinate.

I recently spent about 40 hours reviewing studies related to hibernation and denning in brown bears for a chapter in my book on Brooks River’s bears and salmon, which reminded me just how remarkable this process is. While in the den, bears spend about 98% of their time not moving. Their heart rate declines dramatically from 50-60 beats per minute during summer to 10-20 per minute in hibernation. During this time, they hardly breathe, taking 1.5 breaths per minute on average. Their body temperature drops several degrees entering them into a state of hypothermia. Finally, the metabolic rate of a hibernating bear is 70-75% less than its summer peak. To survive, bears subsist on their body fat, catabolizing it into energy and water.

brown bear sitting on rock surrounded by water

All brown bears, like this adult male known as 89 Backpack, get fat to survive.

Despite their lack of physical activity, hibernating bears maintain muscle strength and bone health. Even if immobilization didn’t cause starvation, osteoporosis, and atrophy in people, we would die of dehydration if placed in an equivalent situation. Hibernating bears, however, are nearly completely self-supporting. The only input they need from the outside world during hibernation is oxygen.

The physiology of bear hibernation is complicated and not fully understood. Scientists are still elucidating basic details about this remarkable process. For example, what causes bears to enter and exit the den? How long do bears need to switch their metabolism from to hibernating mode? As it turns out, the switch is a long process.

Researchers in Sweden used implanted heart rate monitors and GPS-enabled tracking collars on fourteen brown bears. The devices recorded the movement, heart rate, heart rate variability, and body temperature as well as ambient temperature and snow depth. The results, published last year in “Drivers of hibernation in the brown bear,” are insightful because it allowed the researchers to develop correlations between the variables that drive and trigger and hibernation.

In fall, well before hibernation begins, body temperature and heart rate of bears began to decrease. Heart rate started to slow, on average, 24 days before den entry, and body temperature began to drop 13 days before den entry. Overall activity lessened 25 days before entry, but metabolic activity declined steeply just as the bears entered their dens. It took an additional 20 days after for heart rate and metabolic activity to bottom out.

The transition back to a more active physiology started long before bears left their dens. Heart and metabolic rate began to rise one month and 20 days, respectively, before den exit. Body temperature began to rise even earlier, a full two months before den exit when winter still locked the landscape in ice and snow. All bears left the den when their body temperature was 36.7˚C (98˚F) ± 0.15 °C, the active-state body temperature for brown bears. As the researchers note, the narrow temperature range at this time suggests bears exit the den when their body temperature reaches a specific point. Body temperature and metabolic rate stabilized 10 and 15 days, respectively, after den exit, but heart rate didn’t stabilize for another month.

Graph that shows the timing of several variables affecting the start and end of hibernation in bears.

These graphs chart the relationship between physiological parameters of brown bears in Sweden. Den entry (left column) and exit (right column) are indicated by time zero (the green vertical line) to determine the sequence of physiological events. SDANN is the standard deviation of heart rate variability over five minute intervals. It was used a proxy measure of metabolic activity. A red line denotes when a variable was decreasing, while a blue line indicates when a variable was increasing, with the number of days from the entry/exit indicated. From Drivers of Hibernation in the Brown Bear and reposted under the Creative Commons Attribution 4.0
International License.

Even though the bears’ physiology initiates the ultimate beginning and end of hibernation, climate plays a role in this process too. Changes to body temperature before den entry were affected by ambient air temperature, but bears largely relied upon a physiologic slowdown to cool themselves. In spring, bears left the den when the weather was right, exiting when air temperature rose to above 3.7˚C ± 1.5 ˚C (38.7˚F ± 2.7˚F).  Some biologists have suggested that food availability drives the timing of den entry, but this study did not attempt to test the hypothesis.

As a survival strategy, bear hibernation is remarkably efficient, and no other animal attains the same physiologic feats. Small mammal hibernators wake to pee; bears don’t even need to do that. Changing from an active metabolism to one of hibernation and back again takes a lot of time. If you are fortunate enough to see a bear in the middle of fall or the middle of spring, that bear is likely living in a transitional body equipped to handle two worlds—one with food and one without.

 

Filling the Gaps: 274

In the fall of 2016, a bear with a distinctive light-colored patch of fur on its left shoulder was seen at Brooks River. The identity of this bear, at the time, was a mystery. It behaved like it knew its way around the falls and looked like a bear I should recognize.

The problem was I didn’t. So, I speculated. Based on the bear’s shoulder patch, I said it could be 469, a bear who is not often seen at Brooks River but became of interest to webcam viewers in 2013 as he dealt with a leg or foot injury.

Afterwards, the mystery bear was sometimes labeled as 469 in photos and videos.

I was never sure of this ID. The bear’s face, overall fur color, and body size didn’t match 469, but my suggestion fueled further speculation when the bear returned in 2017.

I now know my identification was incorrect. Katmai’s staff has since identified this bear as 274.

bear standing in water with gull in background

Bear 274 Overflow on September 27, 2017. NPS photo.

274 is a maturing adult male and is believed to be the offspring of 438 Flo. Unlike most brown bear cubs, he and a sibling remained with their mother through four summers (most mother bears in Katmai keep their cubs for two to three summers). This is the only example of a brown bear family in Katmai remaining together for four summers.

bear family with older cubs sitting on grassy island

438 (center right) sits with her two 3.5 year-old offspring in 2010. One of these cubs, perhaps the bear on the far left, is believed to be 274.

I never had the opportunity to watch 274 in person in the fall as he is an infrequent visitor, which is perhaps the reason I was mistaken originally. Bears have distinctive features that allow us to identify them across seasons and years. Yet, they can be notoriously difficult to recognize from early summer to fall. 274’s wide-set blond ears and shoulder patch should remain distinctive identifying features during future autumns. His current shoulder patch, it should be noted, wasn’t present in 2012, the last time he was positively identified in the fall.

bear walking in water next to grassy bank

Bear 274 in September 2012. NPS photo.

As he continues to grow, we could see 274 attaining a higher rank in the bear hierarchy. During the last few years he’s not been timid when using Brooks Falls, but he’s also not been large enough to occupy the most preferred fishing spots without being displaced regularly. If genes (which control his potential for growth, health, and lifespan) and fortune (which provide the opportunity for him to attain his physical potential) align, then 274 could become one of the more dominant bears at Brooks River.

brown bear sitting and looking towards camera

Bear 274 in July 2016.

Filling the Gaps

Last July on bearcam, we witnessed the ascent of 32 Chunk in the hierarchy at Brooks Falls. Chunk was the largest bear to consistently use the falls in July, and most bears didn’t challenge him. We watched Chunk interact with many bears, occasionally with some that I (and many bearcam watchers) didn’t recognize. In mid July, for example, we saw Chunk displace another large adult male.

GIF of bear on left moving away from approaching bear who appears at right.

In this GIF from July 2017, a unidentified bear avoids the approach of 32 Chunk.

At the time, a few bearcam watchers speculated the subordinate bear may have been 856, who was the most dominant bear at Brooks River for many years. As I wrote in a previous post, I didn’t think this was 856. So who was it? Was he a previously identified bear or a newcomer to the river?

Before his seasonal position ended this fall, Ranger Dave from Katmai posted photos of several bears who were seen along the river, but were unknown or unrecognized by webcam viewers. Assuming Ranger Dave’s IDs are correct, which they are much more often than not, the unknown bear in the GIF above could be #611.

brown bear standing in water

Bear 611 at Brooks Falls in 2017. Photo courtesy of Dave Kopshever and Katmai National Park.

611 is a bear I don’t know much about. According to my notes, he was first identified in 2015, but only in September and October not in July. Preliminary bear monitoring data from that fall state this bear was an older subadult or young adult at the time.

611_09162015

611 in September 2015, the first year he was identified. NPS photo.

I may be splitting hairs or misunderstanding Dave’s intent, but note that Ranger Dave said, “This is believed to be 611” when he posted the photo. Perhaps there’s still some uncertainty regarding the ID. Filling in the gaps of who’s who at Brooks River can be difficult, and it isn’t possible to identify every bear with certainty. But—based on scars, size, head shape, and ear color—I am fairly convinced the bear in the 2017 photo posted by Ranger Dave is the same bear that Chunk displaced in the GIF above.

At Brooks River, I made the effort to learn to recognize the bears who used the river frequently. Since bear behavior is often complex and can vary from animal to animal, recognizing individual bears leads to a better understanding of their growth, behavior, and strategies for survival. If 611 returns in 2018, we’ll have another opportunity to observe his behavior. Will he challenge other adult males for fishing spots or will he avoid confrontation more often than not? Whatever happens, it will allow us to learn just a little more about the bear world.

Burpee Hill

Dry weather has been infrequent in western Washington this fall, so when a clear day dawned earlier this week I couldn’t resist the opportunity to take a wandering bike ride, one of my favorite pastimes. Over the last several years, my bicycle rides and hikes have become far more leisurely since I have become more prone to distraction. Without a fixed agenda though, I’m more open to discovery. Why, for example, would anyone pass on the chance to see a baby snake?

tiny snake in palm of gloved hand

This tiny garter snake was basking on the side of the road on a warm fall day in late October. Concerned it might become road kill, I moved it off of the pavement.

With temperatures near freezing on Monday, I wasn’t going to find any snakes, but over a fifty mile round trip—from Skagit River to the end of the road near Baker Lake—I found more than enough to hold my attention. After a mere two miles of pedaling, I found a reason to pause.

I began at the old concrete silos in Concrete, a small town along the middle reaches of Skagit River…

Concrete silos. Text on silos reads,

Why was Concrete named Concrete? You only get one guess.

Cycling route profile from Google Maps.

No, I didn’t ride the hill as slowly as Google Maps says it will take.

…and immediately began a steep climb up Burpee Hill. In two miles, the road gains over 800 feet of elevation, although I didn’t mind the opportunity to warm up with frost lingering on the grass.

The North Cascades region is the sum of a complex geologic history. Large-scale mountain building, volcanism, and extensive glaciation created and shaped a landscape of unparalleled ruggedness in the Lower 48 states. This area’s geology is, well, complicated. Just take a look at the geologic map.

screen shot of geologic map of Mount Baker and Baker Lake area

Yikes.

On a bicycle, unlike in a car, stopping to check out roadside curiosities—wildlife, road kill, trees, wildflowers, rocks, scenery—is very easy and is an important reason why I enjoy it so much. About half way up the Burpee Hill climb, I stopped to ponder some interesting sediments exposed in a road cut. The coarse to fine grained sediments were well sorted, indicating flowing water had deposited them, and were capped by a mix of unsorted rocks. This is one piece of a grander glacial puzzle.

view of road cut

A few exposures of loose and coarse sediment can be found on the Burpee Hill Road.

Maps that outline the last glacial maximum in North America give the impression that ice flowed largely north to south. While generally true, the story is a bit more complex on a local scale, as Burpee Hill illustrates.

Glaciers are masses of ice that flow and deform, and they behave differently than ice from your freezer. Set an ice cube on a table and strike it with a hammer and it will fracture. Ice in a glacier’s interior, however, is under tremendous pressure. Ice crystals are altered and deformed like plastic putty, so much so that only the upper 30 meters of temperate glaciers are brittle. (The relatively consistent maximum depth of crevasses reveals this fact. Below 30 meters, deforming ice seals any crevasses. Cavities at the base of glaciers have been measured to seal as fast as 25 centimeters per day.) The ice is not impervious to liquid water though. Within temperate glaciers, ice remains at or slightly above freezing, which allows meltwater to percolate to the glacier’s base. Pressure from overlying ice also causes some water to melt at the bed. Once there, meltwater acts as a lubricant helping the glacier slide. These factors, combined with gravity’s pull, drive glaciers along the paths of least resistance, and sometimes these paths lead uphill.

Between 19,000 and 18,000 years ago, a broad lobe of the cordilleran ice sheet invaded the lowlands of Puget Sound. Fingers of the ice sheet reached into the North Cascades as it continued to advance southward. Around 16,000 years ago, the ice sheet reached its maximum extent in western Washington, reaching south beyond Seattle, Tacoma, and Olympia.

On the margin of the ice sheet, lowland valleys like the Skagit offered ice easy passage as it advanced. About 18,000 years ago in the lower and middle reaches of the Skagit valley, ice flowed in the opposite direction of the modern Skagit River. Burpee Hill is largely the result of this process. It’s a 200 meter-thick layer of glacial outwash, glacial lake sediments, and glacial till deposited at the front of ice as it advanced up the Skagit valley. The features are clearer in a LIDAR image.

LIDAR Image

Burpee Hill is the wedge-shaped feature in the center of the image.

LIDAR image with labels. From left to right:

Glacial ice from the Puget Sound area flowed east over the current location of Concrete. The sediments that make Burpee Hill were deposited in front of the advancing ice.

Since its formation, erosion and landslides have eaten away at Burpee Hill, and it is easy to overlook when the lure of craggy peaks and snow-capped volcanoes always dangles ahead. If volcanoes and orogenies are architects of this landscape, then glaciers are certainly its sculptor, reshaping landforms in profound ways. Stories like this are tucked away everywhere. Landforms are rarely ordinary.

Epilogue:
I continued my ride, which (in case you’re wondering) was wonderful even though temperatures remained near freezing. As I expected it to be on week day in early December, the road was quiet. The views of Mount Baker, pockets of old growth forest, and Baker Lake were worth the effort.
view of snow capped volcano and creek valley

Hey National Parks: You Need More Webcams

Katmai National Park and Preserve is a place of unparalleled resources. It’s studded with over a dozen active volcanoes and protects the site of the largest volcanic eruption of the twentieth century. Its lakes and rivers are swarmed annually by millions of salmon. Abundant food and an undeveloped landscape provides habitat for over 2,000 brown bears, more than any other national park. For 9,000 years people have made it their home, adapting to the landscape’s constant change and challenges.

pumice covered landscape with volcano in background

Mount Griggs towers behind Baked Mountain in the Valley of Ten Thousand Smokes.

As a park, it’s very remote and expensive to experience. Its coastline, measuring over 400 miles, and almost all of the rest of the 4.1 million-acre park remain roadless. For nearly a century after its establishment, Katmai was only accessible to people who could afford to visit and were physically capable of doing so. Webcams (bearcams) changed that.

Webcams allowed Katmai National Park to democratize itself, providing audiences all over the world with meaningful opportunities to connect with the park, especially its bears, and build stewards on a global scale. Survey results* indicate watching the bearcams increased viewer interest in Katmai and wildlife conservation, and viewers’ interest in national parks and wildlife conservation is on par with on-site visitors. Essentially, webcams can inspire stewardship on the same level as a physical visit to a park. They are powerful interpretive tools with great potential to increase awareness, understanding, and stewardship of wildlife and conservation areas. Yet, national parks rarely utilize webcams to their full potential and online audiences are either ignored or deemed secondary to on-site visitors. This needs to change.

bear sitting on rock in river

Bear 708 Amelia sits on a rock–a typical scene on Katmai’s webcams.

Inspired by the success of Katmai’s webcams and to communicate the need to utilize them in more places, I’ll be leading a session at the 2017 National Association of Interpretation Conference. Roy Wood, Katmai’s former Chief of Interpretation and the current Chief of Interpretation and Education at Shenandoah National Park, and Ryan Sharp, Assistant Professor of Park Management and Conservation at Kansas State University will join me. Roy and I will discuss our methods to interpret bears, salmon, and other park resources to online audiences. Ryan will present survey results exploring the online bear viewing experience at Katmai and its influence on support for bear conservation and management.

screen shot of description of conference presentation

If you’re interested in watching but can’t  attend, don’t worry. A presentation about Katmai’s bearcams wouldn’t be complete if it wasn’t streamed live on bearcam. That’s why I made tentative plans with explore.org, who hosts and funds Katmai’s webcams, to live stream the presentation. The session begins at 10:45 a.m. PT on November 16.

In the age of internet and social media, traditional interpretive programs catering solely to on-site visitors (through guided walks, ranger-led talks, slide shows, etc.) are no longer adequate to build and maintain widespread stewardship for parks and other conservation areas. When I worked at Katmai National Park, I was amazed, awestruck really, at the reach and effectiveness of the bearcams. Nearly everyday, I could find evidence of people connecting in meaningful ways with Katmai’s wildlife. Katmai is better protected today than it was even ten years ago due to the awareness and understanding its webcams have brought to people around the world.

The bearcams annually reach tens of millions of people worldwide. With effective interpretation, webcams consistently and positively engage viewers, increase public awareness and stewardship of wildlife, expand messaging to pre and post on-site visitors, and extend interpretive messages to audiences worldwide. Existing technology now provides conservation organizations with the ability to reach people all over the world, not just those who are fortunate enough to visit. We need more webcams and more rangers on them. This is how parks take their message to the world.

Update (Nov. 17, 2017): A replay of my presentation is now online.

Download the slide presentation in PowerPoint (199 MB) or Keynote (127 MB).

*Sharp, Ryan, J. Skibins, and J. Sharp. Online and onsite brown bear viewing: Influence on visitors’ support for conservation-based management at Katmai National Park and Preserve. Unpublished Report to Katmai National Park and Preserve. Kansas State University. Jan. 23, 2017.

Late Season Bears on Dumpling Mountain

Dumpling Mountain, in west-central Katmai National Park, rises gently between Naknek Lake and Lake Brooks. Overridden repeatedly by glaciers during the last ice age, its slopes contour less abruptly than taller mountains to the east. About half the mountain’s topographical prominence lies above timberline. The upper mountain is a chilly, wind-swept place (especially in mid October) where only hardy, ground-hugging shrubs and forbs grow.

tundra and view of low mountain

Tundra on upper Dumpling Mountain on August 22, 2015

snowy tundra

Tundra on upper Dumpling Mountain on September 30, 2015.

The Dumpling Mountain Cam recently captured footage of a mother bear and three yearling cubs there.

The Dumpling Mountain Cam is located about 2,150 feet above sea level on the mountain’s dry alpine tundra, just under 300 feet below and .75 miles distant from the mountain’s 2,440-foot high summit. I hiked up Dumpling Mountain dozens of times, mostly to escape the relative hustle and noise of Brooks Camp, but I rarely saw bears on the mountain. Tracks, sure. Scat, definitely. But bears? Almost never. They don’t use the mountaintop as frequently as other areas. So why would bears venture nearly to the summit of Dumpling now? Are they migrating to a denning site?

Last fall, in a blog post for explore.org, I discussed what is known about the denning habits of Brooks River’s bears. From limited radio tracking studies done in the 1970s, we know these bears probably den on steep, well-vegetated slopes that collect a lot of snow. The same study determined Katmai’s bears denned, on average, at 1,300 feet in elevation.

Dumpling Mountain offers much suitable denning habitat. Although none of the bears radio-collared at Brooks River in the 1970s were tracked to it, I found at least three areas with bear dens in my explorations of the mountain. None are visible within the Dumpling Cam’s viewshed, but they aren’t very far away either.

Screen shot from Google Earth. Purple polygon is viewshed of Dumpling Mountain Cam. Text reads: "Dumpling Mountain Cam" "Bear Dens" "Bear Dens" "Bear Den in Video"

All the dens I found on Dumpling Mountain were around the 2,000 foot elevation line or lower. The purple area represents the Dumpling Mountain Cam viewshed.

Person squatting in entrance to bear den.

Yours truly sits at the entrance of a bear den on Dumpling Mountain.

Bear dens are cozy places. An entrance tunnel leads to a sleeping chamber, which is usually just large enough for the bear crawl into and turn around. Brown bears have the strength and endurance to dig their dens quickly, but den excavation typically takes place over several days. They may also make several excavations near their denning site, perhaps aborting these first attempts due to poor soil conditions.

Bear abundance at Brooks River peaks in late September and early October then decreases coincident with fewer spawning salmon. The bears’ migration away from the river doesn’t necessarily mean they’ll immediately head to their denning site. Bears can still find opportunities to feed elsewhere, even on Dumpling.

These bears on Dumpling may not have been moving to a denning site. Instead, they could’ve been there to eat. Their time on camera showed them traveling, playing, and grazing. Crowberry (Empetrum nigrum), alpine or bog blueberry (Vaccinium uliginosum), and lingonberry (Vaccinium vitus-vitae) all grown on the mountain’s tundra and can be important, and easily accessible foods for bear. Wild berries in Katmai are a fickle crop though. Some years, berry plants produce bumper crops, while in others I was hard pressed to find many berries at all. When one or all are abundant, however, berry-filled scat reveals the bears’ motivation on the mountain. In October, all three species can linger on the bush, but lingonberries are most likely to remain abundant into fall.

 

Dumpling Mountain offers several things bears need—food in the form of seasonally abundant berries, open space relatively free of human disturbance, and pockets of prime denning habitat. Bears using the mountain, especially in the fall, could be there to locate a denning site, to graze frozen berries, or simply on their way from one place to another.

Addendum:

Some bearcam viewers have speculated the bear family recently seen on Dumpling Mountain was 854 Divot and her three yearlings. While the video evidence is inconclusive I saw Divot on Dumpling Mountain in the spring of 2015, so the mountain is part of her home range.

What is Hyperphagia?

Side-by-side comparison of bear in late spring and late summer. Text reads, "747 June 13, 2107" "747 September 11, 2017"

Photos of bear 747 from late spring and late summer illustrate this bear’s substantial weight gain. Photos courtesy of Katmai National Park.

As we’re in the midst of Fat Bear Week, it’s a good time to ponder some of the mechanisms that allow bears to gain enough weight to survive hibernation. Bears get fat to survive and hyperphagia is how they do it. In the bearcam week in review for October 5, I briefly explained hyperphagia. Here it is in case you missed it.

Bears experience hunger in ways humans do not. They need to eat a year’s worth of food in six months or less to survive winter hibernation and the lean months of spring. To do this they eat A LOT, especially at this time of the year. 

In bears, hyperphagia is the period of excessive eating which takes place in late summer and fall. During this time black bears will eat 20,000 calories of food per day. Katmai’s brown bears can easily eat even more by catching calorie-rich salmon. Even though their calorie intake is extremely high, hyperphagic bears don’t feel full.

Satiety is the feeling of fullness after a meal. During hyperphagia, a bear’s body temporarily suppresses the normal mechanisms that balance food intake with weight gain. The body says, “You aren’t full. You don’t have enough fat reserves and need to eat more.” In short, hyperphagic bears don’t feel sated. This contrasts with the excessive eating of bears in June and July when they are eating a lot, but their bodies probably still respond to a feeling of fullness (which is sometimes hard to believe when you watch Otis or 747 catch fish after fish after fish). Hyperphagia, therefore, is a physiological state of bears in late summer and fall, as much as it is a behavior we can see. It’s how they prepare to survive the famine ahead.

747 should be your choice for Fat Bear Week

There are small and fat bears, old and fat bears, young and fat bears, just plain fat bears. But none, NONE I say, are as fat as 747 in 2017. He has earned my official endorsement in the 2017 Fat Bear Week tournament.

fat bear walking in shallow water near grass

747 displays his massive silhouette near Brooks Falls on September 6, 2017.

747 is a mature adult male in the prime of his life. He has gained at least as much and probably more weight than all others. In my opinion, 747 is the biggest and fattest at Brook River.

Compare 747’s overall size in late spring…

Large brown bear

747 in mid June 2017. Photo courtesy of David Kopshever.

…with his fatness in early September.

Fat bear walking in grass

747 is so fat, his belly almost touches the ground.

Still not convinced? Then watch this video of 747 from September 6, 2017.

Since then, 747 has gained even more weight.

Too much fat is unhealthy for humans, but fat is essential to the survival of brown bears. It is a savings account against famine. Without ample fat, bears do not survive hibernation. In spring, often a season of starvation for bears, females with cubs will metabolize fat into milk to nurse their growing cubs, and adult males will use their fat to fuel their pursuit of mates.

747 won’t be rearing any cubs next spring as male brown bears play no role in raising offspring. During a season when almost no high calorie foods are available to bears, 747 will use his fat to roam the landscape for mates instead.

747 faces some tough competitors in this year’s tournament, but don’t fall for any other fat bear propaganda from the fake news mainstream leftwing socialist progressive liberal media. 747 is larger and fatter than any other bear at Brooks River. He’s huge, tremendous, and will win “bigly.”

2017 Fat Bear Week bracket with 747 as champ

This is my 2017 #FatBearWeek bracket. I look forward to seeing your bracket and campaign posters in the bearcam chat on explore.org.

 

 

Testing the Water

At Brooks Falls, most bears tend to focus their efforts at one or two fishing spots. More rarely, a bear will learn to fish successfully almost anywhere at the falls. 503 has used several different fishing spots at Brooks Falls this year—the far pool, near the downed log, the jacuzzi, and the lip. Is he learning to become a generalist angler or will he eventually specialize in a particular spot? Bears from Brooks River’s past and present can offer us some insights into 503’s potential future. Read more in my latest post on explore.org.

Injured Nose Bears

It’s not uncommon to see bears with open wounds and distinctive scars, like bear 83 who seems to repeatedly get injured.

crescent-shaped wound on bear rump.

Photo of 83’s wound from 2015. In 2016, his rump was injured again courtesy of bear 747.

Wounds and the subsequent scars are useful when identifying Brooks River’s bears, since each bear carries a unique suite of them. 83 now sports a large scar on his rump.

Bear standing in white water.

The lump on 83’s rump marks the scar from his 2015 injury.

Sometimes though, we see bears with scars or injuries that may be more than superficial, perhaps impacting the sense they rely on most.

On September 13, 2017, a bear with a large, distinctive scar on his left shoulder was photographed at Brooks River.

1stnite2

Photo courtesy of Lee (aka RiverPA) via Flickr.

Most distinctively, his nose is split.

1stnite

Photo courtesy of Lee (aka RiverPA) via Flickr.

This appears to be an old injury and when I saw these photos I wondered have we seen this bear before?

In 2010 and 2011, a subadult bear with a torn nostril was seen at Brooks River. Bear 253 was a young subadult at the time, but Katmai’s bear monitor was not able to determine its sex. Its nose was most likely injured in 2010 as photos from 2011 show some healing.

 

 

253 probably isn’t the unidentified male photographed with the nose injury this past September though. 253’s muzzle is long and somewhat pointed while the male bear’s muzzle is blockier in shape. The nose injury on the male bear also seems more symmetrical than 253’s.

Would injuries like these impair these bears’ sense of smell? Perhaps, especially if it reduced the surface area inside the nose where scent can be detected.

Bears have a legendary sense of smell. The inside of their nose is filled with many turbinals, a complex scaffold of paper-thin bones. Humans have turbinal bones too, just far less than ursids. In black bears, for example, these bones greatly increase the surface area inside the nasal cavity, providing 100 times more nasal mucosa, or mucous membranes, than humans. More tangibly, if the area of muscous membranes inside the human nose equals the area of your typical postage stamp, then the area covered by mucous membranes inside the black bear nose covers an 8.5 x 11” sheet of office paper. On the surface of the membranes are millions and millions of scent detecting cells. In short, bears live in a world of odors we can scarcely imagine.

Like human eyesight, hearing, and smell, the strength of these senses likely varies in bears. Some bears may have worse eyesight than others (although it’s a myth that bears have poor eyesight; they don’t). Others may have worse hearing. In the case of bears with injured noses, they may not be able to smell as well as their cohorts. (It’s important to note that in the case of 253 and the adult male seen this past September, the injury to their nose may not be deep enough to affect the turbinals.)

If bears are anything though, they are tough survivalists. A nose injury could impose a severe disability on them, but that won’t stop them from doing whatever they need to do to survive.