Last summer, explore.org celebrated the 10th anniversary of the bear cams at Brooks River in Katmai National Park. These webcams offer an in-depth look at the behavior and ecology of a population of brown bears, allow us to observe the same individual bears over many years–giving us the chance to learn about their personalities and habits–and provide a platform for rangers and other experts to host live programs and commentary about the bears and their stories. It’s a wildlife watching experience like no other.
As part of the celebration, I chose to highlight some the moments that I thought were most memorable from the last ten years of bear cam. Some explore point-in-time events. Others celebrate the behavior of individual bears who have left their mark on Brooks River in ways we can’t forget or ignore. Each was unforgettable from my perspective. I hope you enjoy them.
Most Defensive Mother: 128 Grazer
Grazer is an archetypal mother bear. Don’t get in her way and don’t approach her cubs.
Lefty Learns to Fish at Brooks Falls
Old bears can definitely learn new tricks. In July 2015, we watched a fully mature adult male brown bear figure out how to fish where he’d never fished before.
Otis Eats 42 Salmon in a Sitting
Be awed by the capacity of his stomach.
Death of 451’s Spring Cub
When a bear cub falls ill the world will watch.
A lone yearling finds a new family.
Reign of 856
Few bears will ever experience the prolonged dominance and advantage earned by 856.
2020 Salmon Smorgasbord
What happens when bears have access to unlimited salmon? The 2020 salmon run gave us the answer.
History of Fat Bear Week
A goofy idea becomes a world famous internet sensation.
We are Family: 909, 910, and Cubs
Sister bears reunite while raising cubs to create an extended family.
If that’s not enough, the bear cam community complied links to all of our bear cam live events from 2022. Two stand out in my mind: 1. The impromptu Q&A about a fight between and mother bear and a dominant male, and 2. The bear cam 10th anniversary live chat.
We’ve seen a lot of special moments on the cams during the last ten summers–perhaps too many to recall–so these are only a small snippet of the larger story. What are your most memorable moments from the bear cams?
As is tradition—going way back to the before times (2017)—I’ve endorsed a bear for Fat Bear Week. This year’s bracket might be difficult to predict, but with voting commencing today at 12 p.m. Eastern and continuing through October 11, it’s time to throw my weight behind a Fat Bear Week contender.
I’d let him speak for himself but his mouth is usually too full of salmon.
Friends, humans, and ursids, let us stand in awe of a true competitor. A candidate with conviction. A candidate with strength. A candidate that stands up for what he believes. A candidate the size of a double-wide refrigerator. This Fat Bear Week vote for the mighty 747.
747 returns to Brooks River every summer as a giant and just keeps getting bigger.
Perhaps you don’t want to listen to me. After all, I’ve endorsed 747 before and it hasn’t usually led to his victory. Our culture is celebrity obsessed, though, so maybe you’ll listen the expert opinions of these randos.
Homer remarked that 747 is the only other individual whose blubber flies like his.
Pee Wee Herman agreed that 747 was the fattest bear, but he was incredulous when Amazing Larry said he might vote for another candidate.
Dr. Evil threatened world destruction if 747 fails to win.
I spoke with the President too, believe it or not. (He seems to clear his schedule when you have something to say about Fat Bear Week.) Joe Biden noted that 747 grew proportionally faster than this year’s inflation rate.
747’s summer was one of competition and success. In June and July, he yielded space to bear 856. By August, however, 747 turned the tables. He frequently challenged and displaced his long-time rival.
It’s hard work staying dominant and getting fat too. Bears as large as 747 tend to overheat easily, and while their limb bones are built to support their great mass sometimes climbing those hills is a struggle.
You also can’t get that fat without eating a lot of food, and 747 excels in this life goal. Although we don’t know exactly how many fish 747 ate this year, a study about brown bears on Kodiak Island may provide some insight.
Brown bears shed their fur once per year in early to mid summer. Since new fur grows during a bear’s active season, it contains a record of what the bear ate during that time. Studies of captive bears had previously determined the relationship between the mercury content in food and the mercury content in hair. To apply this to bears on Kodiak, researchers first determined how much mercury is found in the Pacific salmon that spawn on Kodiak. They then analyzed the mercury content found in the bears’ hair to gain an estimate of salmon consumption. Large adult males, on average, ate 6,146 pounds (2,788 kg) per bear per year! Some adult males ate a lot more, though, as much as 10,000 pounds of salmon. Since 747 fished at Brooks Falls almost every day between late June and mid September this summer, then his total salmon consumption may likely have been near the upper end of that spectrum.
For fisheries managers and biologists, these statistics are more than pieces of trivia. They are necessary to help inform decisions about salmon escapement goals, so that salmon runs are sustainable for people and the wildlife who depend on them. The aforementioned Kodiak study found that “the estimated population of 2,300 subadult and adult bears [on Kodiak] consumed 3.77 million kg of salmon annually, a mass equal to ~6 percent of the combined escapement and commercial [salmon] harvest (57.6 million kg).” Katmai National Park’s bear population is about as large as Kodiak’s, and when we work to sustain salmon runs we’re also celebrating the life they provide to many other species and individuals, such as bear 747.
Bears get fat to survive winter hibernation, and Katmai National Park’s Fat Bear Week bears are well positioned to weather the oncoming famine. But there’s candidate who eclipses the rest. Your bear might be a 10 but 747 is 1,400 pounds. I’m voting for 747, are you?
Download your bracket from FatBearWeek.org and go there to vote in each Fat Bear Week match from October 5 to 11.
THE THING ABOUT BEARS IS THAT A LOT OF THEM ARE BIG. BUT LIKE HAVE YOU SEEN 747?? HE’S SO BIG. A GIANT, REALLY. HE JUST SITS THERE AND FISHES LIKE THERE’S NO TOMORROW. I MEAN HE HARDLY LEFT THE FALLS ALL SUMMER. DOESN’T MATTER HOW COLD THE WATER IS OR WHICH OTHER BEARS ARE THERE….
Life as a champ is rough. Rivals look to take advantage of any weakness you might show. Arm chair critics analyze your every move. Fans expect perfection. When the next championship tournament rolls into town your body has aged another year and your preferred food has worked its hardest to evade and escape you. Meanwhile, you’re trying to live your best life, because you are a bear and the concerns of humans matter not to you.
Yet, for those of us who recognize greatness and celebrate success when we see it, there is one clear choice for Fat Bear Week 2021—the mighty 747.
Long-time readers of this blog may be thinking, “This again?”
…Let me tell you dear friends: 747 is as fat as ever. He deserves your Fat Bear Week vote.
Brown bears get fat to survive. Their obesity (and it is that since a bear’s body fat percentage is routinely 20-30 percent or more when they begin hibernation) is a savings account. In the den, bears do not eat or drink. They stay warm and hydrated by burning body fat. Unlike utilizing muscle for energy—a process that produces metabolic wastes that must be recycled, sequestered, or purged from the body—burning fat is a relatively clean fuel as I write in chapter 4 of my book, The Bears of Brooks Falls.
It’s akin to cultivating mass only to carefully harvest it later. Just not for vanity’s sake, bro.
747 cultivates mass at an exceptional rate. This summer, he reigned as Brooks River’s most dominant adult male. Even the river’s long-time dominant bear, 856, would not challenge him, and as a result 747 had nearly free access to any fishing spot of his desire.
A single brown bear can eat thousands of pounds of salmon per year. The largest can eat 6,000 to 10,000 pounds. Given his size, appetite, high rank in the bear hierarchy, and his keen fishing skills, 747 is more than capable of eating many thousands of pounds of salmon each summer. At Brooks Falls, he intercepts a great deal of fish by being at the right place at the right time and waiting for his food to come to him. When Brooks River’s sockeye migrated upstream, 747 was primed to harvest them.
He’s so successful that in September 2019 and again in September 2020, he was estimated to weigh more than 1,400 pounds. This places him, as I estimate, among the top one percent of brown bears based on body mass.
Even with his size, he remains agile.
Well, maybe not always that agile.
When he walks close to the webcams at Brooks River, he eclipses the sun.
And yes, that is a tapeworm hanging on for a ride.
Fat Bear Week celebrates the success of Brooks River’s bears, the ecosystem and salmon that sustain them, and the bears’ abilities to get fat and survive. 747 exemplifies success among adult male brown bears. He deserves your vote and a repeat Fat Bear Week victory.
I first traveled to Brooks River within Katmai National Park in early May 2007, and today it’s hard for me to imagine my life without it.
On the morning of my first flight to Brooks Camp (which is only accessible by boat, plane, or a very long, boggy, buggy, and rough cross-country hike), fellow rangers and I hauled our clothing, equipment, and months of food to the floatplane docks along Naknek River in the small town of King Salmon, a sprawling community surrounding an airport and mothballed U.S. Air Force base. We were excited and enthusiastic to begin the adventure, but few of us, I believe, truly understood what we were getting ourselves into. I certainly didn’t. Not quite a greenhorn when it came to wild areas, I had never experienced a landscape like this.
Immediately after takeoff, I gazed out the window of our small plane, my eyes transfixed on what many people would describe as nothing. King Salmon’s few houses, roads, and infrastructure quickly yielded to tundra and scattered spruce trees. This was land devoid of permanent human habitation. Cross hatching animal trails led to unknown destinations. I saw wildly meandering creeks, too many ponds and lakes to count, and a horizon bounded by unnamed mountains.
After twenty-five minutes of flying, the pilot landed smoothly on Naknek Lake’s calm surface, and we taxied to an empty beach in front of the few scattered buildings marking Brooks Camp. With the help of fellow staff, I hurriedly unloaded and stashed my gear inside a nearby tent frame cabin and began to settle in.
Later that evening, Jeanne, my then girlfriend and now wife, and I returned to the beach. I had just finished a winter job at Death Valley National Park, where daily temperatures had already risen above 100˚F, but Brooks Camp looked like winter couldn’t decide to stay or go. Leaves had not broken bud, thick blankets of snow clung to the mountains, and the underground water pipes to our cabin remained frozen. I walked wide-eyed, trying to take in the totality of the scene—the turquoise color of Naknek Lake, the snow-capped mountains, the pumice-strewn beach, a set of bear prints in the sand—when Jeanne waved her arm toward the horizon and remarked, “This is spectacular.”
I don’t recall if I responded or not. Doesn’t matter, because she was right. I had never looked upon land so empty yet so full.
Katmai and Brooks River are unlike any other place. But relatively little has been published about the bears, salmon, and humanity that intertwine at the river. In 2014, I first imagined an idea of writing a book about Brooks River and its inhabitants. In 2016, I began to work on it in earnest and this year I finished the manuscript. I’m pleased to announce my book, The Bears of Brooks Falls: Wildlife and Survival on Alaska’s Brooks River, is available for pre-order. It ships out in March 2021 via Countryman Press. In eighteen chapters, the book strives to explore the ecology of the river’s famed brown bears and salmon as well as the complex relationship people have with the place.
Part one focuses on the colossal eruption of Novarupta Volcano in 1912 and the discovery of the Valley of Ten Thousand Smokes. This event reshaped the area’s history and led to the establishment of Katmai National Monument in 1918, a time when the national park idea was still fledging.
Today, Katmai is most famous for its brown bears. Part two is devoted to their lives and the salmon the bears depend on to survive. I explore the marvel of the hibernating bear from a den on Dumpling Mountain, discover the river from a cub’s perspective, and follow the tribulations and growth of young bears recently separated from their mother. The brown bear mating season provides the chance to learn how bears compete during one of the most important times in their lives. Writing about the bear hierarchy, I consider how this social structure provides advantages to bears who live in an unfair world. Katmai’s brown bears experience hunger in a profoundly different way than people. They must eat a year’s worth of food in fewer than six months to survive hibernation. Their feeding choices and habits reflect highly tuned adaptations to take advantage of summer’s ephemeral bounty. And, the poignancy of a cub’s death, one witnessed by thousands of people on the park’s webcams, provides the chance to reflect on the end of a bear’s life.
Few organisms are as important to an ecosystem as salmon are to Katmai. Leading Odyssean lives, sockeye salmon face tremendous obstacles and challenges. From fresh water to the ocean and back again, they travel thousands of miles, running a gauntlet of predators to fulfill their destiny. Weakened by their freshwater migration and subsisting without food for weeks, the journey of Brooks River’s sockeye ends when they sacrifice their lives to reproduce. They are the ecosystem’s keystone, driving the river’s abundance and significance.
In part three, I examine modern humanity’s influence over Brooks River. Humans may be the river’s biggest ecological wildcard. Climate change looms large over the land and seascapes, and people alter the behavior of the bears that make the scene so special. The infrastructure needed to support thousands of visitors and their recreational activities invite conflict with bears. Managing bears and people in such a small area is especially challenging, provoking a decades-long and often emotional debate about the river’s future.
The Bears of Brooks Falls: Wildlife and Survival on Alaska’s Brooks River is an exploration of brown bears and salmon in one of the Earth’s last fully intact ecosystems. It’s an honest and deep dive into issues surrounding the role people play in the riverscape and Katmai National Park. And, I’m so excited for you to read it, and I hope you’ll consider adding it to your bookshelf.
This blog has been relatively dark over the last year, not because I hadn’t intended to write for it but because I frequently had other writing duties to fulfill. Afterward completing one task, it was often easier to space out at the end of the day than concentrate on writing something that approaches partial intelligence.
I want to share a little of what I have been writing though. Each Tuesday, I cohost a question and answer session in the comments on explore.org’s Brooks Live Chat channel. It’s an AMA about anything related to Katmai National Park’s bears and salmon. Many people submit your questions in advance, which allows me to answer them with greater detail than a question asked on the spot. Below are my answers to those questions during the Q&As for early September.
Be sure to join the Q&A every Tuesday from 5 -7 p.m. Eastern in the Brooks Live Chat channel, and if you prefer to chat in sentences limited to 200 characters, then join the bearcam conversation on explore.org’s Brooks Falls YouTube feed.
September 1, 2020
I’d like to talk about the “Beaver Pond,” which Kathryn asked about via the Ask Your Bearcam Question form. “I’ve often looked at photos of the [Beaver Pond] and wonder if any salmon can make it to the pond and if any of you have seen bears fishing or hunting around the pond?”
The “Beaver Pond” is located about fourth-tenths of a mile south of the outlet of Brooks River. A road provides an avenue to get near there although there is no developed trail to the pond’s edge. Bears use the area but mostly as part of their efforts to get to and from Brooks River because the pond is inaccessible to salmon.
Beavers maintain a lodge on the pond’s north side and a grass-covered dike (an old beaver dam) lines much of that area. But, the Beaver Pond isn’t a true beaver pond in the sense that its formation was the direct result of beavers. It was once part of Naknek Lake and has since been cut off by the sediments deposited by wind driven waves.
The beaver pond was once a cove on the edge of Naknek Lake. Strong easterly winds create waves that erode the gravel shoreline to the southeast of Brooks River. The waves carry gravel and sand northwest toward Brooks River. Over time, a horsetail shaped beach began to encircle the cove. This image below is from an unpublished geologic report about the Brooks River area. Note the concentric ridges along the lakeshore near the beaver pond. These are the beach ridges that cut off the beaver pond from Naknek Lake.
This process is similar to what we see at the river mouth, especially in the “spit” area that partly encloses a lagoon-like area rangers call the boat cove. The boat cove may be destined to become a small pond or marsh like the wetlands between the river mouth and the beaver pond today, although the mouth of Brooks River is more exposed to direct blows from wind-driven waves than the beaver pond area. Strong storms can quickly rework and reshape the gravel at the river mouth.
In the above image, the parallel lines farther inland are old beaches as well, although they weren’t formed by longshore currents. Instead, they mark the former levels of Naknek Lake and Lake Brooks. Naknek Lake has been slowly lowering in elevation as Naknek River cuts through the glacial sediments that dam the lake.
Although we don’t know exactly what the Brooks River mouth area will look like in the future, we definitely know it will not look the same.
Jen wrote in wondering about the line-up of salmon we sometimes see below the river watch cam and asks, “Has that behavior been noted before?” And, “What criteria initiate egg-laying?”
This is the formation that Jen refers to.
Sockeye salmon line up in fairly parallel rows frequently in late summer in the lower Brooks River. Until this year, however, with more salmon using the channel below the river watch cam, we haven’t been able to see this on the cams very well. Although this is not a new phenomenon at the river, I haven’t been able to find an explanation for it. We know the salmon are staging (waiting for the right time to spawn) but I don’t know if lining up in rows gives them any sort of advantage. It may be the most efficient way to sort themselves or there could be some social cue among the fish that prompts the formation. It’s a beautiful feature of the lower river in late summer.
Regarding Jen’s second question, a female salmon lays her eggs in nests she constructs by fanning the gravel with her tail. This action winnows away fine sediments that might hinder water flow (and hence dissolved oxygen) around her eggs. She’s looking for gravel of the right size and in areas of the river with consistent water flow. Males will fan the gravel occasionally too but they play no role in nest construction. Once the female determines her nest is suitable and she’s accompanied by a suitable male, she’ll release her eggs directly into the nest while the male releases his milt. In this way, it is the female who determines when to lay eggs.
LoveTheBears writes, “I understand that there is an area designated for cleaning any caught and kept fish. What happens with the discarded fish parts?”
There used to be a public fish-cleaning building at Brooks Camp. The first iteration wasn’t much more than screened-in shelter with a bucket on the floor where people disposed fish entrails. It was later replaced by a more substantial log cabin style building where people could clean their fish. Today though, there is no public fish cleaning facilities at Brooks Camp and the public is prohibited from cleaning fish within 1.5 miles of Brooks Falls. People can keep one fish per person per day downstream of the bridge, but they must take it immediately to the Fish Freezing Building (the old fish cleaning building) and place it in a freezer. It must remain there until you depart Brooks Camp.
Although no bears at Brooks River are currently conditioned to seek human food, it hasn’t always been this way. In the 1960s and 1970s, many bears learned to associate people with food and sought opportunities to get at human foods at Brooks Camp. The fish cleaning buildings were part of the issue along with open dumps, outdoor burn barrels for garbage, and overall lack of awareness and regulations about proper food storage in bear country. As part of the effort to reduce the risk of bears becoming food conditioned, the NPS got rid of the public fish cleaning facility.
Bears easily learn and remember any trick that allows them to find food. Therefore, we must remain constantly vigilant to ensure that bears don’t learn to associate us with fish. The NPS and the State of Alaska implemented somewhat strict fishing regulations in the 1990s, which has greatly reduced the number of incidents when bears have learned to associate people with fish. Eliminating public fish cleaning facilities and prohibiting fish cleaning within 1.5 miles of Brooks Falls inconveniences some people but it is a big step toward protecting bears.
Angela writes, “We were talking about hibernation in the chat thread and wondered if it is necessary for bears to hibernate. We understand that bears at Katmai hibernate, but were wondering if bears in captivity also hibernate or if because there is a regular food source, the need to hibernate isn’t triggered?”
Hibernation exists along a spectrum rather than being an either/or behavior. Some mammals such as arctic ground squirrels are obligate hibernators, meaning they hibernate regardless of ambient temperatures or access to food. Bears experience a type of facultative hibernation. Given the right circumstances, bears needn’t hibernate to survive winter.
Each year, at least some black bears in mild climates (Sierra Nevada foothills, coastal plain of the southeast U.S., and Big Bend National Park to name a few) remain active all year. These are generally adult males. Similarly, a few adult male brown bears are active on Kodiak all year. Mild temperatures and at least some food allow these bears to remain out and about.
In North America, only pregnant female bears must enter a den and it isn’t because they must hibernate. Bear cubs are born so small and physically immature that they need many weeks of additional development before they are mobile enough to travel with mom. This is even true of polar bears who utilize the winter season to hunt seals on sea ice. Instead of heading out on to sea ice in early winter, pregnant female polar bears, just like all other pregnant North American bears, head to dens to give birth.
Although a handful of bears remain active all year, especially in more southerly populations compared to Katmai, hibernation is a bear’s best energy conservation strategy. It makes sense for nearly all bears to hibernate during winter when food is either very limited or non-existent. For those bears who stay active (other than polar bears), their metabolism and activity rates are much lower than summer. Winter activity, therefore, doesn’t mean that bears are as active as they would be in summer. So even captive bears may ignore food and water provided to them, relying more on their hibernative physiology to survive.
Erin asks, “747 is a huge bear. Is he the biggest bear seen at Brooks River? Have there been bigger bears in the past?”
As I’ve said and written many times, 747 is a giant of a bear. He is the most massive bear I’ve ever seen and we should not take his presence for granted. If 747 were to disappear from the river, it may be a long while before we see another as big as he. Last year, 747’s was estimated to weigh more than 1,400 pounds.
Each year, there are comparably sized bears in Katmai and at Brooks River. I’ll start by listing three of the currently seen bears who approach 747’s size class and then highlight two who might have approached it in the past. Only the largest adult males are comparable.
Right now 32 Chunk, 151 Walker, and 856 are close to 747’s size (at least within 300 pounds or so). They certainly rival him when measured by height and length. Each of these bears seem smaller to me than 747, but looks can be deceiving. Size is also an important determinate of dominance in the bear world. It is not absolute though. While 747 is more dominant than Chunk and Walker, 747 consistently yields to 856.
In the past, Brooks River has hosted some very big bears. While I never had the opportunity to see Diver in person, he was reportedly extremely fat and large in his heyday during the 1980s and 1990s. Look at this photo as an example.
In 2007, the most dominant bear I saw at the river was 24 BB. He was very tall and long–so a massively framed bear. He didn’t use Brooks River in late summer though so we never got to see BB at his peak size for the year. BB behaved much like 856. He asserted his dominance frequently and spent less time fishing than 747 does today, so he might not have been as heavy as 747 but the potential was there.
Marlene writes, “856 is getting older. I am wondering if he will know when he no longer can hold the top spot or do you think there will have to be a confrontation?”
856 has been the river’s most consistently dominant bear since 2011. Like all bears, 856 is great at weighing risk versus reward. For him, the overall risk of confronting other bears is low and provides great reward in the form of access to food, fishing spots, and mating opportunities, because other bears recognize his dominance. 856 will use that to his advantage as long as he can.
His high level of dominance is tied to his health and fitness. He’s a large bodied bear so will remain relatively dominant no matter what but he needs to maintain his good health and fitness in case another bear challenges him or is unwilling to yield. 856 might fall from the top of the hierarchy if he is defeated in a fight by another comparably sized bear.
His reign as the river’s most dominant bear could end in another way though. He might not feel up to the challenge.
In July 2017, 856 was an infrequent visitor in July and when he did show up, he yielded easily to 32 Chunk, perhaps because he suffered from a leg injury that hindered his ability to compete with other comparably sized males. At the time, already after many years of dominance, I thought this was the end of 856’s reign at the top. I was wrong. 856 returned to the return to the river in September 2017 looking as healthy as ever and acting as dominant as ever. He hasn’t taken a step back since.
The chances of a repeat of July 2017 could be in 856’s future just as much as his defeat in an intense fight at the paws of another bears. If 856 continues to return to the river as he ages into his early and mid 20s, I think we’ll see at least one of those scenarios play out.
Across much of North America, tucked within isolated dens, a new generation of bears is beginning their lives.
Mother bears spent much of the last year preparing for this event. Although the timing varies among species and individuals, North America’s bears mate in late spring and early summer. The fertilized eggs, however, do not immediately implant in the uterus, undergoing only a few cell divisions before they enter a state of arrested development. During this process of delayed implantation, the female goes about her business while embryos remain in suspended animation. Implantation and fetal growth renew only close to the time she enters her winter den. Afterward, bear fetuses gestate for 6 – 8 weeks.
The gestation time is remarkably short for such a large mammal, and it produces especially tiny and helpless cubs. Brown bear cubs, for example, weigh a scant pound and measure only 8 – 9 inches long at birth, about the size of a beagle puppy. They are also born blind, lightly furred, and nearly immobile. Their ears are closed and their muzzles are short with a round, toothless mouth. Newborn cubs are so underdeveloped and small that they cannot maintain their own body heat in the den and must remain in contact with their mother to stay warm. About the only thing they can do is scream, which, not unlike human newborns, they employ frequently to gain their mother’s attention. It’s hard to imagine large adult bears so helpless, but they all start life this way.
Newborn black bear cubs. U.S. Fish and Wildlife Service photo.
The small size of newborn cubs is surprising for animals that weigh several hundred pounds when fully grown. Generally, larger mammal species have longer gestation periods and give birth to larger offspring than smaller mammal species. African elephant calves gestate for nearly two years and are born bigger than elk calves; elk calves gestate for about eight months and are born bigger than deer fawns; deer fawns gestate for seven months and are born bigger than fox kits; etc. But, bears break the rule by a considerable margin. Bears give birth to the smallest offspring in comparison to adult female body size of any mammal.
Cubs are only 1/200th the size of even the smallest reproducing female grizzlies and commonly 1/500th or less for large adult brown and polar bears. In contrast, newborn human babies are an order of magnitude larger than bear cubs. A 10 pound child born from a 150 pound woman is 1/15th the size of its mother (yeah, I know that’s a big baby but the math was easy). Additionally, offspring born to large mammals are generally precocial, i.e. they are at least somewhat and sometimes highly mobile soon after birth. Bear cubs, however, are more akin to helpless hatchling birds or pinky mice. There is no parallel among placental mammals—only marsupials give birth to offspring as undersized as bears.
But why are bear cubs born purposefully premature? Why not just have a longer gestation time and birth larger, more independent cubs? The short gestation period and the relatively small size of bear cubs at birth both appear to be an adaptation to maximize the use of fat.
Bears are the only mammals that give birth while hibernating, a time when they do not eat, drink, urinate, or defecate. Survival during this time is dependent on stored body fat, but the paradigm poses a problem for expectant female bears. A developing mammal fetus cannot metabolize free-fatty acids, perhaps because these substances do not cross the placenta as readily as sugars and protein. So, as long as a bear tries to sustain fetal growth through her placenta, she needs to draw energy from her own body protein. Fetuses also produce bodily waste, which is transferred to the mother and adds to her physiological challenges. To cope, bears evolved an alternative strategy, one that allows her to give birth while hibernating, support the continued growth of cubs, and keep the family safe.
Unlike in the womb, baby mammals can metabolize fat shortly after birth and milk is the vector to deliver it. Bear milk is a particularly rich and nourishing substance. Brown bear milk, for example, is about 22% fat by volume. Polar bear milk is even richer, a whipping cream composed of over 30% fat. By shortening the gestation period, mother bears trade placental nourishment (mostly protein and sugar) for mammary nourishment (mostly fat) and tap into the one resource they have in abundance.
Female bears utilize their fat reserves to support the growth and nourishment of their cubs.
On a diet of fatty milk, a brown bear cub can gain about a 1/5 of a pound of body mass per day, weighing about 5 pounds when one month old and 15 – 25 pounds by 90 days. Not coincidentally, this is about big as they would be if gestation was of an “expected” length like other placental mammals. The den, therefore, becomes a surrogate womb, protecting the family during the most vulnerable time in their lives.
Polar bears play at the entrance to their mother’s den. These cubs are probably several weeks old. U.S. Fish and Wildlife Service photo.
Bears face many obstacles to survive and reproduce, not the least of which is winter famine. Hibernation provides bears with the ability to outwit winter by surviving on accumulated fat, but during this time a female bear must support the growth of her cubs with nothing more than the energy stored in her body. Given the challenges posed by gestation, hibernation, and winter famine, the birth of a bear represents a remarkable and unparalleled feat of mammalian adaptation.
This was a busy year on the bearcams, courtesy of explore.org and Katmai National Park. We hosted more live broadcasts this year than any other year since the bearcams first went live in 2012.
During play-by-play broadcasts Katmai rangers and myself narrated the Brooks River’s wildlife activity, much like broadcasters for sporting event (although the lives of brown bears and salmon is no game). We never knew what might happen during a play-by-play. Watching the prolonged posturing between two of Brooks River’s largest adult males, 856 and 32 Chunk, on July 12 and integrating the ranger’s radio traffic into the September 17th broadcast are two of my favorite play-by-play moments.
The other broadcasts, live chats, typically focused on a specific topic such as bear fishing styles, hibernation, and bear research at Brooks River. Rangers Andrew LaValle and Russ Taylor from Katmai joined me as frequent co-hosts for live chats and I was also fortunate enough to speak with many special guests. Perhaps the most memorable moment from these broadcasts occurred when bear 132 and her spring cub almost stepped on Ranger Andrew and I during our Katmai centennial live chat on September 24.
I was busy on a keyboard this year, even though there were long gaps between posts on this site. In case you missed them, here are the posts that I wrote for explore.org in 2018. They are listed in the order they were posted. My personal favorites include “How does a bear family breakup,” “How many salmon will a bear eat,” “Bearcam live chat surprise,” and “Living with Bears in Churchill.”
Bear 856: On Top Again: Bear 856 appears to be big enough and healthy enough to show the river’s other adult male bears he’s ready to compete once again.
Death of a Bear Cub at Brooks River: As the smallest and most vulnerable of all bears, first year cubs (also called spring cubs or cubs-of-the-year) face significant risks and challenges, not the least of which are larger bears.
Dumpling Mountain Hike: Rising over 2000 feet above Brooks River, Dumpling Mountain offers anyone a quick escape from the hustle and bustle of Brooks Camp. Each time I hike on it, I get an opportunity to see the land in a new way.
Four Cubs for 402 Again: No matter this family’s fate, we can marvel at 402’s determination to follow her maternal instincts in an attempt raise another generation of Brooks River’s bears.
How Does a Bear Family Breakup? Until somewhat recently, I stated that 402 had “abandoned” her yearling (now known as 503). While this might be true in a sense, I no longer think that this is an accurate way of describing the event. After reading more about the emancipation process, I’ve come to believe 402 didn’t abandon her yearling in 2014. She emancipated him.
How Many Salmon will a Bear Eat? We often observe bears partake in marathon fishing sessions at Brooks Falls, so how much can they eat in a day or season? Quite a lot.
Salmon on the Underwater Bearcam: The calmer, deeper water near the outlet of Brooks River provides salmon with a temporary refuge that is relatively safe and costs them little energy.
451 and Her Yearlings: 451 is currently raising her second litter, and it’s easy to see that the family is skinner than many of the other bears on the bearcams.
Fishing By Snorkeling: Efficient and effective, snorkeling is one of the best strategies to scavenge fish.
Can a Bear be Too Fat? When you see bears whose stomachs appear to drag on the ground, one wonders if a bear can grow too fat for its own good.
Bearcam Live Chat Surprise: “This being a live broadcast it’s entirely possible…a bear could walk through the screen at any time. So if we have to exit or end the broadcast abruptly that’s probably why.”
Evidence of Rapid Change in Katmai: the Ukak and Savonoski Rivers spill across a broad, 1.5-mile wide delta. In a landscape often defined by change, this is one of the most dynamic places in Katmai National Park.
2018’s Top Ten Bearcam Moments: the people have spoken! Bearcam viewers have chosen the top ten bearcam moments of 2018. Each moment is unique and significant for a different reason.
Living with Bears in Churchill: The confluence of bears and people in this remote community has created a special set of challenges, which can only be met through the town’s willingness to tolerate the largest four-legged predator on Earth.
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.
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.
“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
“I keep my distance from him because I’m concerned he’ll roll on top of me.” Bear 68
“I’m still in awe of his size. Can he even dig a den big enough to fit within?” Bear 402.
“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
“747 is a role model of fat bear success. I hope to be as fat as him one day.” Bear 503
“I’m too hungry to comment.” Bear 480 Otis.
Many people who have observed 747 closely also agree with the endorsement.
“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.
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.
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.
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.
Two wolves tear into a moose carcass soon after a brown bear left it unattended. Photo courtesy of Anela Ramos.
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.