Survival Skills of the bears

[Deleted]

Apr 8, 2019 2:33:05 GMT -5 brobear said:

Apr 8, 2019 1:59:11 GMT -5 @londonbluebear said:

And the only other predator to make it to polar bear habitat. They have learned how to hunt seals.

Remember though; it was grizzlies who first conquered the high arctic and comparatively rapidly evolved into polar bears.

True. If grizzlies can learn to hunt seals, polar bears can learn to hunt bovids.

[brobear]

www.eurekalert.org/pub_releases/2019-12/osu-ept121919.php?fbclid=IwAR0pJ9p4QcxVdanQqBKv9tSuzaGZmnBlZK50edW6N-3szKIER4ITnuu-NCw

NEWS RELEASE 19-DEC-2019
Easy prey: The largest bears in the world use small streams to fatten up on salmon

CORVALLIS, Ore. - It's a familiar scene to anyone who's watched footage of brown bears catching sockeye salmon in Alaska: They're standing knee-deep in a rushing river, usually near a waterfall, and grabbing passing fish with their paws or jaws.

But a new study published in the journal Conservation Letters reveals a different picture of how and when bears eat salmon. Most of these bears, also known as grizzlies, are dipping into small streams to capture their iconic prey.         
 
                                                                                

[tom]

Interesting study. Good find.

[brobear]

Bears as predators....

The size of a carnivore strongly influences the size of the prey it is capable of killing, the maximum size of prey killed being slightly larger than that of the predator. For example, a 100 kilogram (220 pound) bear can handle prey weighing up to roughly 150 kilograms (330 pounds). Polar bears prey primarily on the smallish (60 kilogram/ 130 pound) ringed seal and the larger (up to 360 kilogram/790 pound) bearded seal. In some instances, polar bears can remove up to 44 percent of the ringed seal pups born in a particular area. They are also known to kill walruses (500 kilograms/1,100 pounds) and white whales weighing up to 600 kilograms (1,320 pounds).

Brown bears, while primarily vegetarian, can also prey significantly on hoofed mammals. In some areas, adult males reportedly kill three or four adult moose (450 kilograms/990 pounds) per year, with females killing an average of one. Caribou (150 kilograms/330 pounds), musk ox (250 kilograms/550 pounds), elk (200 kilograms/ 440 pounds), and bison (500 kilograms/ 1,100 pounds) have all been taken. Brown bears also prey on ground squirrels, trout, and salmon, but usually only when they are sufficiently abundant to make hunting them energy-efficient.

ANDREW E. DEROCHER AND IAN STIRLING, Bears: Majestic Creatures of the Wild (1993).

[brobear]

www.bearbiology.org/fileadmin/tpl/Downloads/URSUS/Vol_3/Rogers___Rogers_Vol_3.pdf

Parasites of Bears: A Review

INTRODUCTION

This paper is an attempt to summarize the available information on parasites of bears. Knowledge of ursine parasites has expanded considerably since the subject was reviewed by Stiles and Baker in 1935; more than 90 additional reports on the subject have been published, and at least 43 additional parasites have been reported. In this paper, available information is summarized for each of 77 species of parasites, including (1) species of host, (2) pathological effects, (3) whether hosts were captive or wild, (4) the proportion of the bears from a given geographic location that were infected, and (5) sources of information. Parasites also are listed by host. Topics discussed include transmission of trichinosis and parasitism during hibernation.

[brobear]

The brown bear is omnivorous and a poor tree climber (except the cubs)
(Clark, 1959; Craighead and Craighead, 1972;Herrero, 1978; Mealey, 1980; Aoi, 1985; Ohdachi and Aoi, 1987; Boertji et al., 1988; Gasaway et al., 1992).
Adaptation of the hindlimbs for climbing in bears
www.ncbi.nlm.nih.gov/pubmed/15900701
By the way:
"...The hunter may escape by climbing a tree; for although young grizzlies can climb like a cat, the old bears can do nothing more than stand on their hind-legs in vain endeavors to reach the branches where the man lies concealed, and growl spitefully. Their extreme heaviness, however, is thought by the Indians to be all that prevents them from climbing..."
www.gutenberg.org/files/28984/28984-h/28984-h.htm

[OldGreenGrolar]

Den site selection by male brown bears at the population’s expansion front.


Brown bears (Ursus arctos) spend about half of the year in winter dens. In order to preserve energy, bears may select denning locations that minimize temperature loss and human disturbance. In expanding animal populations, demographic structure and individual behavior at the expansion front can differ from core areas. We conducted a non-invasive study of male brown bear den sites at the male-biased, low-density western expansion front of the Scandinavian brown bear population, comparing den locations to the available habitat. Compared to the higher-density population core in which intraspecific avoidance may affect den site selection of subordinate bears, we expected resource competition in the periphery to be low, and all bears to be able to select optimal den sites. In addition, bears in the periphery had access to free-ranging domestic sheep during summer. We found that males in the periphery denned on high-elevation slopes, probably providing good drainage, longer periods of consistent, insulating snow cover and fewer melting-freezing events. Forests were the principal denning habitat and no dens were found in alpine areas. The Scandinavian brown bears have a history of intense harvest, including culling at the den. This may have exerted a selection pressure to avoid denning in open alpine habitat which compared to forests provide little cover. The bears denned away from main roads and in steep, rugged terrain, probably limiting human access. The odds for finding a bear den decreased with increasing distance to the population core where females could be found. Previous studies have documented directed movement of male brown bears from the male-biased population periphery toward the core areas during the mating season. In this way, denning males may be trading off between low resource competition and access to sheep in the low-density periphery, and mating opportunities in the higher-density population core.


Introduction

In areas of high latitude, the winter season presents animals with the challenges of low temperatures and reduced food availability. Animals show a range of physiological and behavioral adaptations to these conditions, such as migration [1], food caching [2], metabolic rate reduction [3], seasonal changes in fur, plumage, and fat deposits [3, 4], and hibernation [5]. Across much of their Holarctic range, brown bears (Ursus arctos) spend 5–7 months of the year in winter dens [6–9]. During hibernation, they lose 20–45% of their body weight [10], and selecting a den site that minimizes energy loss is therefore essential [7]. Furthermore, dens provide cover for security [11]. Through history, denning bears have been vulnerable to humans [12–15]. In Scandinavia during the 1800s, culling at the den was one of the most common bear hunting methods as it was considered the most effective way of reducing bear numbers [13, 14]. In addition, den abandonment due to human disturbance has substantial energetic costs and has been linked to increased cub mortality [15–20]. Therefore, bears may select den sites that minimize human disturbance [21–24].



In expanding animal populations, population structure, genetic diversity and individual behavior at the expansion front can differ from core areas [25–34], and hence, findings from population cores may not be transferrable to peripheral areas. Such demographic and behavioral differences have been found in expanding brown bear populations in different parts of Europe [31–36]. The Scandinavian brown bear population has expanded considerably after being functionally extinct in Norway by the 1940s and reduced to a population low of about 130 individuals in several small, isolated areas in Sweden, by 1920–30 [30, 37]. The dispersal is male-biased, whereas the females reside mostly within defined population core areas, still almost exclusively on the Swedish side of the national border (Fig 1A) [38–41]. South-Eastern Norway is now at the population’s expansion front, and like peripheries of other expanding brown bear populations [31–33], consisting primarily of males dispersing from the core areas [30, 37, 41] to which they periodically move back for the mating season, presumably to get access to females [42]. Even though some bears in South-Eastern Norway are shot in association with livestock depredation and in later years during licensed hunts, the number of bears shot per year is low. For more than 100 years and until after our study period, no female bears were confirmed killed in this peripheral area [43]. The habitat quality is similar along the core-periphery gradient [44], except for free-ranging domestic sheep which are common in Norway during summer and early fall, but not available in Sweden [42, 45, 46]. Hence, the low density and male-skewed sex ratio west of the national border are results of the male-biased population expansion, and not due to harvest or unsuitable habitat [30, 37, 44]. On the contrary, sheep provide an additional source of lipids and proteins for bears in the periphery.





Fig 1

Study area.

(A) Location of the study area Hedmark County in South-Eastern Norway (green) and brown bear population core areas (blue) [38] on the Scandinavian Peninsula. (B) Hedmark County with major cover types forest (green), alpine (yellow), cultivated land (brown), lakes (blue), rivers (black lines), and the location of 174 dens used by brown bear males from 1976 to 2014. Black dots represent 120 dens used by 64 different males identified by DNA, and black triangles represent 54 dens used by unidentified males (see Methods).


Denning behavior and selection of denning habitat have been investigated previously for Scandinavian brown bears in the southernmost population core area (Fig 1A) [9, 24, 47, 48]. In this area, bears most often dig their dens into anthills or soil, or hibernate on a nest of sticks and branches on the ground, or under rocks [9, 48]. Males have been reported to enter their dens between 5 October and 18 November (mean = 27 October), possibly triggered by the first snowfall, and leave their den before the snow has melted, between 6 March and 25 April (mean = 4 April) [9]. Bears in the core area have been found to prefer den sites in open canopy pine forest, at lower altitude, easterly aspect and steep slopes, and to avoid roads, water, peat, exposed bedrock, and deciduous and alpine mountain-birch forests [47]. However, there has been no den site selection study in the periphery of this population, and hence it is not known whether individuals at the expansion front show similar denning preferences to those in the higher bear-density core areas. In the population core, intraspecific avoidance may affect den site selection of females and subadult males which were found to den closer to occupied houses and plowed roads, possibly to avoid adult males [47, 48]. Also, the preference for lower altitudes in the population core may be attributed to avoidance of dominant males as it was evident only in females and subadult males [47, 48]. In the periphery, home range sizes increase as the bear density drops, but without a decrease in habitat quality [44]. Hence, intraspecific interactions and resource competition should be low [36, 44], and even young males may be able to select optimal den sites. The low competition and access to sheep in the periphery may compensate for the travel distance to the core areas during the mating season, especially for young males.



By non-invasive field methods, we conducted the first study of winter dens used by brown bear males at the expansion front of the Scandinavian brown bear population, within Hedmark County in South-Eastern Norway. We expected that brown bear males in this periphery could optimize their den site selection to maximize heat preservation and minimize human disturbance without having to trade-off with intraspecific avoidance. To preserve heat, we hypothesized that bears in the periphery would den at high elevation (H1) and avoid southerly aspects and high potential solar radiation (H2), thus providing a longer period of consistent, insulating snow cover and fewer melting-freezing events [49, 50]. We also hypothesized that denning bears would avoid water and peatland, and den on slopes for good drainage (H3). To minimize human disturbance, we hypothesized that dens would be located preferentially in steep, rugged terrain to limit human access (H4), in forested areas providing shelter (H5), and away from human structures (H6). Finally, we hypothesize that males in the periphery would prefer to den relatively close to the population core to facilitate access to females (H7).


www.ncbi.nlm.nih.gov/pmc/articles/PMC6116945/

Looks like male bears prefer to be in areas where mating is accessible.

[OldGreenGrolar]

There is still more to read in the link. The article is long.

[brobear]

Brown bears that live high up in the barren Himalayan mountains can average within the 200-pound range while those of the lush coastal regions of Alaska and Russia can weigh well over 1,000-pounds. This incredible size variation which is controlled by environment and food availability is among the brown bear's greatest survival attributes.

[OldGreenGrolar]

Oct 3, 2021 1:19:49 GMT -5 brobear said:

Brown bears that live high up in the barren Himalayan mountains can average within the 200-pound range while those of the lush coastal regions of Alaska and Russia can weigh well over 1,000-pounds. This incredible size variation which is controlled by environment and food availability is among the brown bear's greatest survival attributes.

Brown bears like Kodiak bears and ABC bears also show that they are able to adapt in isolated islands.

[brobear]

In an effort to protect their cubs, grizzly sows will often stay in a location close to the road.
Julie Argyle

[yz]

With nowhere to run, the sloth bear would choose to confront the tiger instead :

[brobear]

Jun 6, 2020 8:45:25 GMT -5 brobear said:

Jun 5, 2020 23:58:06 GMT -5 OldGreenGrolar said:

The stamina of the barren ground grizzly is astounding! Especially when we consider this this plantigrade beast is not even built well for running. Great find GreenArctos. 

Power, stamina, and a determination that no big cat can match.

[brobear]

Change of heart keeps bears healthy while hibernating

www.sciencedaily.com/releases/2011/02/110207142625.htm

Hibernating, it turns out, is much more complicated than one might think. New research illustrates a complex series of changes that occur in grizzly bears' hearts as they hibernate. The changes guard against complications that could arise from greatly reduced activity.

Hibernating, it turns out, is much more complicated than one might think.

Research published in the latest issue of the journal Physiological and Biochemical Zoology illustrates a complex series of changes that occur in grizzly bears' hearts as they hibernate. The changes guard against complications that could arise from greatly reduced activity.

A grizzly hibernates five to six months of the year. During that time, its heart rate slows drastically from around 84 beats per minute when active to around 19. "If a human heart were to slow down like this, you'd see very detrimental things happening," said Bryan Rourke, a professor at Cal State Long Beach who worked on the research with his graduate student, Nathan Barrows.

Such a slow beat causes blood to pool in the heart's four chambers. In a human, the increased pressure would cause the chambers to stretch out. The dilated muscle would be weaker and less efficient, leading ultimately to congestive heart failure.

"Bears are able to avoid this," Rourke said, "and we're interested in how they do it."

Barrows and Rourke worked with Lynne Nelson and Charles Robbins, researchers at Washington State University who have been studying bears for years. They operate a facility at Washington State where grizzlies have been raised since birth and acclimated to echocardiogram testing. Research at the facility is providing crucial insight into the mysteries of the hibernating heart.

Nelson and Robbins had previously shown that, during hibernation, the muscle of a bear's left ventricle stiffens to prevent it from stretching as blood accumulates. But the stiffening of the ventricle presents another problem. The left atrium, which pushes blood into the left ventricle, must then work against greater resistance.

"The atrium is pushing against a brick wall," Rourke said. "We thought there must be some kind of mechanism to keep the atrial muscle from wearing itself out."

Using echocardiogram data from the captive bears at Washington State and tissue samples from wild bears, the researchers found that the atrium protects itself by weakening its beat.

Muscle contractions in the heart are controlled by a protein called myosin heavy chain. The protein comes in two varieties, alpha and beta. The alpha version produces a quicker but slightly weaker contraction compared to the beta. "We found that the muscle in the left atrium produces more alpha protein during hibernation, which results in a slightly weaker beat," Rourke said. "The lower force keeps the atrium from being damaged as it pushes against the stiffer ventricle."

When the bears emerge from hibernation, the protein ratio switches back and the atrial contraction returns to its original strength.

The researchers believe this is the first study to show a shift in myosin ratio in bears, and they hope the information might someday have an application for humans.

"Bears aren't a perfect model for humans, but the way in which a bear's heart can change could be helpful in understanding human disease," Rourke said. "It's a really interesting physiology."

[brobear]

Hibernating bears' ability to regulate insulin narrowed down to eight proteins
Date: September 21, 2022

www.sciencedaily.com/releases/2022/09/220921113127.htm

Feeding honey to hibernating bears helped researchers find the potential genetic keys to the bears' insulin control, an advance that could ultimately lead to a treatment for human diabetes. Every year, bears gain an enormous amount of weight, then barely move for months, behavior that would spell diabetes in humans, but not for bears whose bodies can turn insulin resistance on and off almost like a switch. In the hunt for the bears' secret, scientists observed thousands of changes in gene expression during hibernation, but now a research team has narrowed that down to eight proteins.

Feeding honey to hibernating bears helped Washington State University researchers find the potential genetic keys to the bears' insulin control, an advance that could ultimately lead to a treatment for human diabetes.

Every year, bears gain an enormous amount of weight, then barely move for months, behavior that would spell diabetes in humans, but not for bears whose bodies can turn insulin resistance on and off almost like a switch. In the hunt for the bears' secret, scientists at WSU observed thousands of changes in gene expression during hibernation, but now a research team has narrowed that down to eight proteins.

"There seem to be eight proteins that are working either independently or together to modulate the insulin sensitivity and resistance that's seen in hibernating bears," said Joanna Kelley, a WSU evolutionary geneticist and corresponding author of the study published in iScience. "All of these eight proteins have human homologues. They're not unique to bears. The same genes are in humans, so that means maybe there's a direct opportunity for translation."

The research team analyzed changes in bear cell cultures that were exposed to blood serum drawn from grizzly bears housed at the WSU Bear Center. Both the cells and the blood serum were taken from the bears during active and hibernating seasons as well as from an interrupted hibernation period when researchers fed the bears honey-water.

In the lab, the researchers combined different cell cultures and serums, such as a cell culture from a hibernation season with serum from the active season, to analyze the genetic changes that occurred.

Through all the combinations, it was the serum from the mid-hibernation feeding period that helped the most in identifying the key proteins.

"By feeding the bears just for two weeks during hibernation, it allowed us to control for other things like daylength and temperature as well as food availability," Kelley said.

Bears do typically get up and move a little during hibernation, but they usually do not eat, urinate or defecate. The researchers used these waking moments to offer the bears honey-water, one of their favorite treats, as part of another study, which found the extra sugar did disrupt their hibernation behavior. Kelley and her colleagues then used the samples from that study period to do their genetic analysis.

When the researchers put the serum from the disrupted hibernation onto a cell culture taken from regularly hibernating bears, they found that those cells started to exhibit changes in gene activity similar to that of active season cells.

Next, the team plans to investigate how those proteins specifically work to reverse insulin resistance, research which could ultimately lead to the development of ways to prevent or treat human diabetes.

"This is progress toward getting a better understanding of what's happening at the genetic level and identifying specific molecules that are controlling insulin resistance in bears," said Blair Perry, the study's co-first author and a WSU post-doctoral researcher.

The tools for understanding genetics are becoming more sophisticated, and recently Kelley, Perry and their colleagues published an updated genome assembly for brown bears, of which grizzly bears are a subspecies. This more complete, contiguous genome may help provide even better insights into bear genetics including how they manage hibernation.

"There's inherent value to studying the diversity of life around us and all of these unique and strange adaptations that have arisen," said Perry, who has also studied the genetic makeup of snake venom. "By understanding the genomic basis of these adaptations, we gain a better understanding of what we share with other species, and what makes us unique as humans."

Other researchers on this study include co-first author Michael Saxton along with co-authors Brandon Evans Hutzenbiler, Shawn Trojahn, Alexia Gee, Anthony Brown, Omar Cornejo, Charles Robbins and Heiko Jansen all of WSU as well as Michael MacCoss, Gennifer Merrihew and Jea Park of University of Washington.

[brobear]

While the most common timeline is 200,000 years ago, not all paleontologists agree on this exact time, but nearly all agree that sometime during the last Ice Age, a group of brown bears roamed far up into the high arctic where they learned to hunt seals on the ice flows. Those brown bears, in time, as they adapted, evolved into our modern polar bears. Those brown bears were omnivores. They had to adopt to a full-carnivore diet of blubber. But, they were successful in this drastic change.

Big cats are full-time predators and carnivores, yet, even though there were both tigers and lions living in cold climates, in brown bear country, they never made it up as far north as the high arctic. Perhaps neither cave lions nor tigers could survive such extreme cold as a brown bear. Notice that there are no polar lions or polar tigers.