bears

Fat Bear Week 2018 Endorsement

/ Mike Fitz / 16 Comments

Last October I wrote, “There are small and fat bears, old and fat bears, young and fat bears, and just plain fat bears. But none, NONE I say, are as fat as 747.” A year later, 747 continues to demonstrate his survival skills and success at Brooks River. He’s big enough and fat enough to once again earn my official endorsement for Fat Bear Week 2018. 747 is titanic, a giant among bears.

GIF of large, dark brown bear walking down a steep hill

Bear 747 is an adult male in the prime of his life. First identified as a subadult bear in 2004, he’s matured into the largest bear I’ve ever seen.

 

747 on July 5, 2018.
747 on September 10, 2018.

But don’t just take my word for it. Bear 747 is endorsed by several of his competitors at Brooks River.

bear lying on ground

“Look, we’re all fat right now, but no one is as fat as 747. Seriously, his belly nearly drags on the ground. Even I never achieved that level of pudge. “ Bear 410

profile of bear walking along edge of river

“I keep my distance from him because I’m concerned he’ll roll on top of me.” Bear 68

402_07062016

“I’m still in awe of his size. Can he even dig a den big enough to fit within?” Bear 402.

bear with blond ears and blond coat standing in water

“Even though I’m in the Fat Bear Week bracket, I still might vote for 747. It’s the logical vote. He probably weighs at least three times as much as me.” Bear 719

profile of brown bear standing on edge of waterfall

“747 is a role model of fat bear success. I hope to be as fat as him one day.” Bear 503

bear sitting in water below waterfall

“I’m too hungry to comment.” Bear 480 Otis.

Many people who have observed 747 closely also agree with the endorsement.

bear lying in water facing photographer

“He’s all business—fishing and eating. Nobody gets fat like 747.” Jeanne R., former Katmai National Park ranger.

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.

Other bears might be more charismatic or tug on your heartstrings, but 747 truly is a giant among Brooks River bears. He deserves your vote for Fat Bear Week 2018.

Katmai Fat Bear Week Bracket 2018 Fitz choices.png

My 2018 Fat Bear Week bracket predictions.

You are encouraged to vote for Brooks River’s fattest bear on Katmai National Park and Preserve’s Facebook page. Starting on Oct. 3, park rangers will post head-to-head matchups between well-known bearcam bears. The bear whose photo receives the most likes will advance to the next round, until one bear is crowned fattest bear on Fat Bear Tuesday, October 9th. Don’t forget to watch Katmai’s fattest bears on bearcam.

 

 

 

A bear, wolves, and a moose carcass

/ Mike Fitz / 4 Comments

Although they probably inhabit all of Katmai National Park, wolves are infrequent visitors to Brooks River, and seeing a wolf on the bearcam is a noteworthy occasion.

Late one evening at the end of June and about a dozen miles from Brooks River, I was lucky enough to see wolves compete with a bear for food along the middle reaches of Margot Creek.

At the beginning of the video, a blob in the middle of the creek represents the bear as it laid on the moose carcass. Two park rangers observed the same bear on the moose about seven hours before (no one witnessed how the moose died). When presented with a large animal carcass, bears will often bury it and/or sleep directly on it to protect it from other scavengers.

Not long after I started to watch the bear, a wolf emerged from the forest. It circled the bear, perhaps testing how tolerant or defensive the bear might be. Bears are quick, capable of outrunning any human, but they aren’t as fast as a wolf, and wolves know this. Therefore, the wolf was in little danger from the bear as long as it remained wary and stayed out of the bear’s reach. This didn’t stop the bear from charging the wolf several times though (only a few of which I was able to record). Despite the bear’s defensiveness, the wolf was persistent.

low resolution photo of a bear running at a wolf

A bear defends a moose carcass by charging a wolf who approached too closely. Photo courtesy of Anela Ramos.

Soon after the wolf appeared, the bear left the carcass and a second wolf arrived. The wolves didn’t appear to be in sufficient numbers or aggressive enough to chase the bear away. Perhaps the wolves were enough of an annoyance that the bear was unable to rest or the bear could’ve been chilled by lying on the carcass in the creek for several hours. Whatever the reason, after the bear left for good the two wolves quickly began to gorge on the moose. They focused their efforts on the moose’s abdomen, thoroughly eviscerating it within fifteen minutes.

grainy photo of two wolves eating a moose carcass in a creek

Two wolves tear into a moose carcass soon after a brown bear left it unattended. Photo courtesy of Anela Ramos.

Shortly afterward, stomachs bulging with moose entrails and meat (wolves can eat over 20 pounds of food in a single feeding session), the wolves sauntered into the forest.

Events like this happen in many places where wolves and bears share habitat, but in Katmai it might be more intense in spring and early summer before spawning salmon become abundant across the ecosystem. Bears often steal the show at Katmai, but wolves also prowl the landscape, following their own strategies for survival and sometimes competing directly with bears for food.

Return to Bearcam 2018

/ Mike Fitz / 14 Comments

As many readers of this blog are aware, one of my favorite places in the world is Brooks River in Katmai National Park. There, about 300 miles southwest of Anchorage, Alaska, brown bears and salmon gather to create one of the most iconic scenes in America’s national parks.

many bears standing and fishing near a waterfall

Brooks Falls on a busy evening

 

I’m pleased to announce that through the generosity of explore.org, I’ve received a fellowship to work with Katmai’s bearcams, live streaming webcams of at Brooks River.

In conjunction with Katmai’s park rangers, I’ll write blog posts (which you can read on explore.org and Medium), chat frequently in the bearcam comments, and host live chats and play-by-play style broadcasts. I hope to make time to write about my other explorations on this blog as well.

Bearcam season is almost upon us. Webcam technicians are at Brooks River now, upgrading the webcams for a better live cam streaming experience. The first sockeye salmon should arrive at Brooks River in a matter of days and the bears will arrive soon after. This will be an exciting summer, so please join me here and on bearcam.

Hibernation Hangover

/ Mike Fitz / 4 Comments

In Glacier National Park, Montana, a black bear has emerged from hibernation, but hasn’t left his tree cavity den.

According to the park website, this bear was first seen on March 23. Since then, the black bear, who is male, has mostly rested in the tree cavity. After a long winter of hibernation, you might assume a bear would be eager to get moving and find something to eat, but bears often don’t leave their denning site for days, sometimes weeks, after they emerge in the spring.

A bear fresh out of the den isn’t the same bear it will be in May. Immediately after emerging from their dens, bears are active but neither hungry nor particularly thirsty. In one of the first studies on the physiology of hibernating bears, researchers found captive bears ignored food and water for up to two weeks and some bears didn’t begin to eat and drink normally for three weeks after they emerged from their dens. One grizzly bear didn’t even urinate for two days after it emerged. (In contrast, during another study a black bear in the fall urinated copiously, producing eight to sixteen liters of urine per day.)

This annual life stage of springtime bears has been described as “walking hibernation.” Compared to summer and, especially, early fall, bears in walking hibernation are hypophagic. They actively ignore food and drink little water while still surviving on body fat. During walking hibernation, bears experience an internal transition from full hibernation to a more active physiology. Research on brown bears in Sweden, which I wrote about previously, has found the body temperature and metabolic rate of brown bears doesn’t stabilize until 10 and 15 days, respectively, after den emergence and their heart rate doesn’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.

bear feet sticking out of hole in tree trunk

The transition from hibernation to fully active includes lots of resting. Screen shots from the Glacier National Park bear den live stream.

black bear in tree cavity

Possibly because their metabolism and heart rate remain somewhat low, many bears seem to loathe leave their dens, at least right away. So, it’s not uncommon for bears to remain near their denning site while their bodies transition back to more active levels.

The bear at Glacier will leave its tree cavity den relatively soon. His hunger will grow as his metabolism returns to active levels. His libido will increase too, and he’ll begin to prowl the land for females in estrous (the mating season for black and grizzly bears peaks in late spring). Compared to other stages in their annual cycle, less is known about the first few weeks of life for bears after they emergence from hibernation. It is rare for us to witness a bear’s life at this time. With webcams and other digital tools like GPS collars, we’re gaining a greater depth of knowledge about many wild animals. Glacier’s webcam provides a rare opportunity to observe a bear shortly after it has emerged from hibernation. Like most bears right now, it remains in a bit of a hibernative hangover.

The Difference Between Brown and Grizzly Bears

/ Mike Fitz / 5 Comments

For my book on Brooks River’s bears and salmon, I find myself digging deep into natural history and ecology of brown bears. Sometimes I uncover research that challenges my long held assumptions. Take the difference between brown and grizzly bears, for example; something I often said was mostly based on geography and diet. As I wrote for Katmai’s website:

All grizzly bears are brown bears , but not all brown bears are grizzly bears. Grizzly bears and brown bears are the same species (Ursus arctos), but grizzly bears are currently considered to be a separate subspecies (U. a. horribilis). Due to a few morphological differences, Kodiak bears are also considered to be a distinct subspecies of brown bear (U. a. middendorffi), but are very similar to Katmai’s brown bears in diet and habits.

Even though grizzlies are considered to be a subspecies of brown bear, the difference between a grizzly bear and a brown bear is fairly arbitrary. In North America, brown bears are generally considered to be those of the species that have access to coastal food resources like salmon. Grizzly bears live further inland and typically do not have access to marine-derived food resources.

These geographic and dietary distinctions seem simple enough. However, there is little scientific evidence to support it. Both brown bears and grizzly bears exist, but the differences between them aren’t what I had long assumed.

bear grazing on vegetation with travertine and forest in background

A grizzly bear grazes on springtime vegetation near Old Faithful in Yellowstone National Park.

bear in water

A brown bear at Brooks Falls in Katmai National Park. (NPS Photo)

Although North American brown, grizzly, and Kodiak bears belong to the same species, Ursus arctos, bear taxonomy underwent many revisions before scientists reached this conclusion. In the nineteenth and twentieth centuries, taxonomists frequently lumped and split brown/grizzly bears into many different species and subspecies. The separation peaked in 1918 with the publication of C. Hart Merriam’s Review of the Grizzly and Big Brown Bears of North America in which Merriam proposed around 80 (not a typo) species and subspecies of North American brown bears. Taxonomists like Merriam relied on morphological characteristics that could be seen or observed to classify living and extinct organisms. Warm-blooded animals that have hair, breathe air, and produce milk for their offspring are mammals, but warm-blooded and air-breathing animals that lay eggs, have feathers and toothless beaks are birds. These are greatly simplified examples, I realize, and such tidy and clear distinctions aren’t necessarily common in nature. They often become more difficult to resolve at the genetic and species level, especially in cases of hybridization or when taxonomic distinctiveness is based on subtle physical differences.

Merriam’s nuanced classifications of brown and grizzly bears were based on differences in skull morphology and dentition, characteristics he examined painstaking detail. Among taxonomists, Merriam was a splitter. On southeast Alaska’s Admiralty Island alone, he classified five distinct species . In the Katmai region, Merriam described two species, Ursus gyas for the Alaska Peninsula and Ursus middendorffi for Kodiak Island , as well as others for bears living in the Cook Inlet area and on the Kenai Peninsula.

If you think his classifications of brown/grizzly bears was a little over the top, you’re not alone. Merriam foreshadowed opposition to his conclusions when he wrote in his Review, “The number of species here given will appear to many as preposterous . To all such I extend a cordial invitation to . . . see for themselves.” And they did. Most of the species or subspecies described by Merriam were later regarded as local variations or individual variants. While all of Merriam’s species have since been lumped together as U. arctos, in the mid 1980s as many as nine extant or extinct subspecies of U. arctos were recognized in North America , but the only names for North American brown bear subspecies in still widely used are U. a. horribilis, the grizzly bear, and U. a. middendorffi, the Kodiak bear. Recently, however, even these classifications have come under question.

In hindsight, it’s easy to scoff at Merriam’s conclusions. Could there really be dozens of brown bear species in North America? Within the methodologies and knowledge of his era, his results aren’t that far fetched. Little was known about the behavior, growth rates, ecology, and population dynamics of North American bears in the nineteenth and early twentieth centuries. Given access to the same tools and information as modern taxonomists, Merriam may have discovered grizzly and brown bears can’t be so easily divided by differences in skull and tooth shape.

Ursus arctos is one of the most widely distributed mammal species on Earth. Historically, brown bears were found from the British Isles south to North Africa and east across northern and central Asia to Alaska and most of western and central North America. Two to three million years ago, they split from a common ancestor shared with black bears . The oldest brown bear fossils are from China and date to about 500,000 years ago. By 250,000 years ago, they spread to Europe. During the last 100,000 years of the Pleistocene, bears immigrated and emigrated across much of the northern hemisphere as climate and habitat dictated. When continental ice sheets advanced, available habitat shrunk and bears became isolated into separate populations. When the ice receded, bears dispersed into the new territory. Beginning around 70,000 years ago, the first brown bears moved into North America. While we know when and where bears lived and live from fossils and historical records, this doesn’t necessarily deduce the genetic relatedness of modern populations.

Phylogeography is a branch of phylogeny, the evolution of an organism or group of related species or populations. As such, phylogeography traces the distribution of genetic variation through time and space. In this regard, mitochondrial DNA (mtDNA) is especially useful to track female ancestry. MtDNA  resides in the mitochondrion, a cell’s powerhouse, and is inherited from the mother only, unlike nuclear DNA which is a recombination of genes from both parents. According to mtDNA analysis, there is no divide between brown and grizzly bears based on an animal’s relationship to the coast or marine food sources, nor does it support the status of U. a. horribilis or U. a. middendorffi or any other historical subspecies in North America. The only historic classification that holds is at the species level—Ursus arctos. Instead, matrilineal ancestry suggests brown bears in North America fall into three main clades.

  • Mainland Alaska, Kodiak Archipelago, and northwest Canada.
  • ABC Islands (Admiralty, Baranof, and Chichagof) in southeast Alaska.
  • Southwestern Canada (Alberta, British Columbia) and the lower 48 States.

Clades are groups of organisms evolved from a common ancestor and consequently share a genetic relationship. The three North American clades, as well as others in Europe and Asia, are believed to be descended from brown bears living in isolated populations in Asia during the late Pleistocene . Since then, the mtDNA has remained geographically separated due to the tendency of female brown bears to be homebodies. Female brown bears are philopatric. They tend to remain near or have partly overlapping home ranges with their mother and do not rapidly invade areas already occupied by other brown bears . This can prevent or at least greatly slow mtDNA from mixing into other bear populations, even long after significant barriers like ice sheets have disappeared.

screen capture of Earth with clades of bears outlined.

Approximate range of brown bear clades in North America based on mtDNA. Different clades are represented by horizontal and vertical lines. The solid red circle marks the location of brown bears on the ABC islands.

Bears on the ABC Islands are the most genetically distinct of all Ursus arctos. Their mtDNA aligns them more closely to polar bears than to other brown bears , a genetic uniqueness most likely resulting from interbreeding with a small number of isolated polar bears at the end of the last ice age. Since then, female brown bears on the islands have not spread their polar bear genes to the mainland. Bears in British Columbia, Alberta, and into the lower 48 represent another lineage who arrived in Alaska around the same time as the ancestors of the ABC bears. During a warm interglacial period, some of these bears moved south into the mid continent before the ice advanced again and sealed them off from their brethren to the north.

All other brown bears in northwest Canada and Alaska, including those on Kodiak, belong to a clade that dispersed from Asia in two separate waves. Those in northwest Canada arrived first, perhaps as early as 33,000 years ago. Bears now occupying mainland Alaska represent the last pulse of ursine migrants onto the continent, arriving just before rising sea levels flooded the Bering Strait and closed the land bridge between Asia and North America. Excluding the ABC islands, all Alaskan brown bears belong to this pedigree, which stretches from northwestern Canada and Alaska west across Russia and into Europe and includes most of the world’s brown bears.

The results from mtDNA only convey information about the maternal line, however. MtDNA cannot trace genes spread exclusively by male brown bears, so it underrepresents the role of males in gene flow. Male brown bears have larger home ranges and disperse away from their mother’s home range more readily than females, especially during their first few years of independence. Males do carry one important bit of DNA that females don’t—the Y chromosome. Like mtDNA, it is only inherited from one parent, but unlike mtDNA it can only be passed from father to son, making the Y chromosome an important marker to trace paternal gene flow and diversity.

While mtDNA shows particularly strong clade differentiation  across the entire range of Ursus arctos, geographic variation in the Y chromosome of brown bears is much shallower . According to analysis of the Y chromosome, no deep genetic or geographical divergences could be found from bears in Eurasia or North America. Brown bears on the ABC islands and mainland Alaska, for example, share closely related haplotypes (a group of genes inherited from a single parent ) found in the Y chromosome. Even brown bears from populations as separate as Norway and the ABC islands have been reported to carry highly similar Y chromosomes . Male genes, therefore, flow across clades.

infographic showing hypothetical inheritance of mitochondrial DNA and Y-chromosome through three generations of bears.

Within mammals, mitochondrial DNA can only be inherited through the maternal line. The Y chromosome is only passed from father to son. MtDNA tends to stay within genetically related clades because female bears are philopatric. Male bears, due to their inclination to disperse farther and have larger home ranges than females, can spread Y chromosomes over bigger areas. Unlike nuclear DNA, neither mtDNA nor the Y chromosome are a mix of maternal and paternal genes.

This isn’t to imply male bears from the Yukon immigrate to Europe or vice versa, just that males are more apt to wander and set up home ranges well away from their mother. If female brown bears, due to their philopatry, differentiate a population’s genetics over time, then male bears homogenize it. In other words, female brown bears like to stay in familiar terrain, but males often spread their seed far and wide.

With evidence of geographically isolated clades through mtDNA but not in the Y chromosome—can we still divide brown bears into biologically significant units? Even though genetic research adds another dimension to our understanding of wildlife, morphology remains an important way to differentiate species, and subspecies don’t necessarily need to be from separate or unique ancestry to be worth protecting. Grizzly and brown bears still exist, just not along a clean geographic and dietary divide. Where we draw the line is less important than the overall conservation of bears. Populations of brown bears—whether they are from Katmai, Kodiak, or Yellowstone—remain ecologically and culturally special no matter their genetic distinctiveness. Bears in Yellowstone are geographically and (at least currently) genetically separated from other “grizzlies.” Kodiak bears aren’t genetically distinct enough to justify them as a separate clade even though they have been isolated from mainland bears for approximately 12,000 years. Hypothetically speaking, if bears are extirpated from Kodiak or Yellowstone then they won’t be coming back and a valuable repository of genetic diversity will be lost forever.

The line between a brown bear and a grizzly, as I used to define it, was always tenuous at best. (Should grizzlies in interior Washington, British Columbia, and Idaho—who may have fed on salmon before runs in the Columbia and Snake watersheds collapsed—be considered brown bears?) Now through DNA analysis we know Ursus arctos cannot be so arbitrarily split based on their geographical closeness to the ocean. It’s still ok to say grizzly, Kodiak, or brown bear—the names can still be incredibly powerful and useful—but maybe the only truly accurate name for them is Ursus arctos.

References:

Bidon, T. , et al. Brown and polar bear Y chromosomes reveal extensive male-biased gene flow within brother lineages. Mol. Biol. Evol. 2014. 31(6): 1353-1363.

Davidson, J., et al. Late-Quaternary biogeographic scenarios for the brown bear (Ursus arctos), a wild mammal model species. Quaternary Science Reviews. 2011. 30:418-430.

Rausch, R. L. Geographic Variation in size in North American brown bears, Ursus arctos L., as indicated by condylobasal length. Canadian Journal of Zoology. 1963. 41(1): 33-45.

Schwartz, C.C. et al. “Grizzly Bear,” in Wild Mammals of North America: Biology, Management, and Conservation. 2nd Edition. Editors Feldhamer, George A., Bruce C. Thompson, and Joseph A. Chapman. John Hopkins University Press. 2003.

Talbot S. L., et al. Genetic characterization of brown bears on the Kodiak Archipelago. Final Report to Kodiak National Wildife Refuge, U.S. Fish and Wildlife Service. 2006.

Waits L. P., et al. “Genetics of the bears of the world.” In Bears: Status Survey and Conservation Action Plan. Compiled by Christopher Servheen, Stephen Herrero, and Bernard Peyton. IUCN/SSC. 1999.

Waits, L. P., et al. Mitochondrial DNA Phylogeography of the North American Brown Bear and Implications for Conservation. Conservation Biology. 1998. 12(2): 408-417.

 

Drivers of Hibernation

/ Mike Fitz / 10 Comments

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 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

/ Mike Fitz / 8 Comments

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

/ Mike Fitz / 3 Comments

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.

Late Season Bears on Dumpling Mountain

/ Mike Fitz / 8 Comments

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.

Lingonberry (Vaccinium vitis-idaea)
This dark purple bear scat is filled with black crowberry (Empetrum nigrum).
Bog or alpine blueberry (Vaccinium uliginosum)

 

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?

/ Mike Fitz / 3 Comments
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.