Post by Gorilla king on Nov 7, 2022 16:41:44 GMT -5
Grizzly Crossing
This sow grizzly was collared and known as bear 264. For many years she lived along a stretch of park road in Yellowstone and was viewed by lots of visitors. A few years ago bear 264 was hit by a car and killed in the park. On a morning in May several years before she died, I came upon bear 264 with her two cubs of that year at Obsidian Creek. The grizzly sow spent several minutes attempting to convince her cubs to cross the small creek. She would stand by the cubs and vocalize, then jump the creek to demonstrate what she wanted and then call to them some more. The cubs whined a lot, but would not cross the stream. After jumping back and forth several times, bear 264 took note of all the people watching and ended the lesson on how to cross a stream. She then led her cubs away from the road and all the spectators. Grizzly bear cubs learn many of the skills they need to survive from their moms during the first two and a half years of life. YOU CAN USE THE SLIDESHOW FEATURE TO SEE WHAT HAPPENED.
A grizzly bear sow demonstrates where she wants her cubs to go by jumping the creek.
After jumping the stream the sow grizzly bear calls to her cubs to follow.
The mother grizzly stands on the bank and encourages her cubs to cross the creek. The little grizzlies called out to her, but wouldn't cross.
The mother grizzly bear jumps the stream again to retuen to her cubs.
Here the female grizzly jumps back to her small cubs after they refused to join her on the other side of Obsidian Creek.
The female grizzly looks around and sees all of the tourists and photographers who have stopped and are watching her from the roadside and nearby turn out.
After taking stock of all of the people and several unsuccessful attempts to get the cubs to cross the stream, bear 264 joins them on the far bank.
The cubs stand up to get a better view of the people watching before their mom leads them off.
Post by oldcyansilverback on Jan 29, 2023 6:23:20 GMT -5
After centuries of persecution, brown bears are showing up in some unexpected places.
January 26, 2021
A bear emerges from dense vegetation and pauses on the shore. It’s early spring, and the young grizzly has only recently roused from hibernation, ravenous and driven. He lifts his head and gazes out across the falling tide to the opposite shore, where forested slopes are close enough to make out individual trees. The bear stands and sniffs the air.
Grizzlies can see about as well as we can, but it’s their olfactory powers—at least 2,000 times more acute than ours—that most likely set them in motion. We’ll never grasp how they perceive the world, let alone what they’re thinking. For some reason, this bear falls back on all fours, ambles away from prime habitat, and wades into the sea.
To reach the far shore, he dog-paddles west across Johnstone Strait, one of the narrowest navigable channels that make up the fabled Inside Passage. This stretch of water separates the North American mainland from the largest island on the Pacific coast, British Columbia’s Vancouver Island. It’s only three to 4.5 kilometers across but anywhere from 70 to 500 meters deep. Swift tidal currents can reach 15 kilometers per hour. Vessels of every description pass through, from kayaks, to freighters, to cruise ships carrying thousands of passengers. At this time of year, the water temperature averages about 8 °C, but the bear has almost no fat left to insulate him from the cold.
When he finally shakes off on the other side, the bear arrives in a place much like he left behind: dense stands of hemlock, cedar, and fir—coastal temperate rainforest—a grizzly Shangri-La. All that’s missing is other grizzlies. There are plenty of black bears and cougars about, but grizzlies are conspicuously absent. Maps showing the historical range of grizzlies color virtually the entire Pacific coast of North America but leave Vancouver Island oddly blank. And yet, in the spring of 2020, at least seven grizzlies were spotted roaming the island’s east coast. Although sightings have increased over the last 20 years, the island doesn’t have a viable grizzly population. Locals say that, after causing a stir, some of the interlopers are captured and returned to the mainland, a few become nuisances and are killed, and most eventually swim back to the mainland on their own.
Why do they come to the island only to leave again? What are they moving away from, or to? Could these bears be part of a larger, global pattern of expanding grizzly populations? These questions lead to an ice age mystery and a glimpse of a possible future.
From his home office 260 kilometers east of Johnstone Strait, Bruce McLellan has a deep and wide perspective on the state of the world’s bears. The wildlife research ecologist, who lives in a small, unincorporated community on the BC mainland, reports that the news on grizzlies is good. In fact, over the 40-plus years he’s spent studying them, things have never been better. McLellan recently retired from full-time work with the provincial government but remains committed to research. He’s a past president of the International Association for Bear Research and Management and is the Red List Authority for the International Union for Conservation of Nature (IUCN) Bear Specialist Group, which supports the conservation of seven of the world’s eight remaining bear species and their habitats worldwide. (Polar bears have their own specialist group.) The population of grizzlies in southern British Columbia has been going up over the past few decades, he says, after we spent the previous two centuries trying to annihilate them.
“We’re getting more and more bears on the coast and more and more generally throughout the southern part of the province,” McLellan says. Five of the six populations he’s been monitoring are stable or increasing with annual rates up to seven percent, although one is in slow decline. This represents a remarkable turnaround.
To understand what’s happening today, it’s important to know that by the end of the 20th century we had eradicated grizzlies from over half of their historical range. In western North America, early European settlers identified grizzlies as threats to their livestock and agricultural crops. They also feared them as threats to human safety. For these reasons, settlers vigorously pursued and destroyed grizzlies. In British Columbia, the government paid bounties for their hides. When, as a society, we finally stopped shooting them on sight, McLellan says, the populations got a chance to recover. A recovering grizzly population means more young males—and they are programmed to disperse.
In British Columbia, some head north along the coast, some go east into the interior, and a few head west, swimming to Vancouver Island and smaller coastal islands. Coastal grizzlies can range for hundreds of square kilometers, depending on the habitat. The fact that they’re reclaiming habitat—and showing up in places we’ve never seen them before—should come as no surprise.
Say you’re a hungry young bear living in good habitat. What goes through your mind as you look across Johnstone Strait to Vancouver Island?
“You might be thinking, well there are no breeding opportunities here for quite a few years because I’ve got to deal with all these big dudes. I’m not gonna have a chance,” McLellan says. But he doubts it’s a cerebral thing. A lot of bear behavior is instinctual. Essentially, young male grizzlies are destined to wander until they find a place they like.
To some biologists, grizzlies are a brown bear subspecies; to others, they are just North America’s version of brown bears (U. arctos), a species that once roamed across much of the northern hemisphere. In North America, the historical range of brown bears stretched from the north coast of Alaska, where they still roam, to the northern half of Mexico, where they’ve long been extinct. Brown bears have thrived in a wide variety of environments, from alpine and tundra to grasslands, forests, and deserts. Although classed in the order Carnivora, brown bears are omnivores that take advantage of whatever food is available. In fact, they mostly eat plants. Like us, their adaptability to landscape and diet helps them succeed.
Christina Service is a young wildlife biologist on British Columbia’s central coast, 300 kilometers north of Johnstone Strait, in the village of Klemtu. She currently works for the Kitasoo/Xai’Xais Stewardship Authority, and is close to the beginning of her career. She calls speculation about why a grizzly would swim away from prime habitat toward an unknown island “the million-dollar question.”
In 2014, she documented and published her findings about the bears colonizing islands along British Columbia’s central coast, now known internationally as the Great Bear Rainforest. On these islands, she found young adult male grizzlies, which she calls “quintessential teenagers” predisposed to test boundaries and establish new territories, but she also found females with cubs. The narrowest gap separating these islands from the mainland is only about 300 meters.
The bears’ shift west, from the mainland to the islands, has been swift, Service says. “There are some underlying environmental conditions that have changed, and quite dramatically, to allow that shift to happen.”
She points to the history of industrial forestry, which altered landscapes, estuaries, rivers, and streams, and the decreased availability of salmon, as having contributed to the shift over the last century. Now added to the mix is climate change, which affects when and where vegetation becomes available. Coastal grizzlies are renowned for their photogenic seasonal salmon feasts. Less well known is their dependence on what’s called the “green wave,” during which vegetation reaches its nutritional peak in stages as the snowpack retreats. In increasingly warmer years, this vital food source greens up all at once. Service’s work documented grizzlies moving to islands and using this outer coastal landscape “in a way we typically don’t ascribe to grizzlies,” she says. Fishing for sea urchins, for example.
Service says that big range changes like the one documented on British Columbia’s central coast can be thought of as a canary in a coal mine, a warning that significant environmental shifts are underway—shifts driven by human activity.
North America has almost 60,000 brown bears, or grizzlies; approximately 54 percent live in Alaska and 25 percent live in British Columbia. South of the Canada-US border, they are also expanding their numbers and range. Montana and Wyoming are seeing an increase in grizzly densities of around three percent per year. Today, there are somewhere between 1,200 and 1,400 grizzlies in the contiguous United States. There is growing support for (as well as opposition to) reintroducing them in several western states, including California, which still prominently features a brown bear on its flag despite the fact that they were hunted to extinction in that state. The last reported sighting of a California brown bear was in 1924.
In Europe, brown bears are also increasing their numbers and expanding their range, especially in Norway and Sweden, where the population has gone up from around 1,000 bears in 1930 to roughly 3,400 today. After having eliminated or severely reduced their brown bear populations, Italy, Austria, and France are now reintroducing them to parts of their former range. In Western Europe, their stronghold is the Carpathian Mountains, which stretch through seven countries, including Romania, Ukraine, Poland, and the Slovak Republic. There, the brown bear population appears to be stable. For brown bears living throughout the rest of Eurasia, the story is less optimistic. Both brown bears and Asiatic black bears (U. thibetanus) are under increasing threat from poaching to supply the black market with bear gall bladders, paws, and other parts used in traditional Chinese medicine.
Back in North America, in addition to island-hopping along the west coast, brown bears are also heading north. The IUCN has had to redraw the brown bear range map to reflect this recent shift. Vast regions of the Arctic formerly considered polar bear territory are now brown bear range, including the west coast of Hudson Bay and Manitoba’s Wapusk National Park, which is famous for its polar bears. In the Arctic Archipelago, brown bears now roam a landscape significantly altered by climate change. They are taking over polar bear territory—and encroaching on their DNA.
Banks Island is a vast, treeless expanse of tundra and snow in the western Arctic Archipelago. The Inuvialuit people have found instances on the island of polar bears and brown bears reproducing, resulting in hybrid bears that share characteristics of both species. These individuals are not sterile like mules—horse-donkey hybrids—they produce fertile offspring. This reveals their close genetic heritage. In terms of evolutionary time, polar bears recently evolved from the brown bear line and moved into, learned to exploit, and became fully adapted to the Arctic environment in the past 500,000 years. But the Arctic is changing fast. The temperature is rising at three times the global rate, the sea ice is disappearing, and the tundra is turning to mud.
”Brown bears are expanding their range into polar bear habitat. The two species have begun to interbreed, creating hybrid offspring."
How did brown bears get to Banks Island? The shortest route is through neighboring Victoria Island, where the crossing from the North American mainland is 23.5 kilometers. The resident polar bears are phenomenal swimmers and are called sea bears (U. maritimus) for good reason. One female polar bear was recorded as having swum 687 kilometers over a period of nine days. Brown bears? Not so much. They are strong swimmers, but prefer to stay close to shore. Bruce McLellan estimates that, based on research done on the genetics of brown bears in Alaska’s Alexander Archipelago, male brown bears will swim up to seven kilometers, females no more than two. The brown bears arriving on Banks Island must have arrived by walking across seasonal sea ice.
McLellan believes the mystery of why there is no viable grizzly population on Vancouver Island likely comes down to that gap of three to 4.5 kilometers separating it from the mainland, and the difference between the distance male and female brown bears are willing to swim. That’s why the grizzlies seen arriving on Vancouver Island will almost certainly be young males. When they get there, he says, they find suitable habitat, but no chance to mate.
Around much of the world, when given the chance or forced by circumstance, brown bears are expanding their range. Just as a changing Arctic results in brown bears moving north today, evidence from a previous era of climate disruption holds clues of them moving south to Vancouver Island.
Some 60 kilometers west of Johnstone Strait is a rare karst landscape overlain with clearcut forest. For eons, water has dripped and coursed through the limestone mountains on northern Vancouver Island, creating a network of caves. Inside the rubble-choked entrance of one of those caves, discovered in 1993, the remains of three bear species were found. The cave would become known as Pellucidar, after the fictional subterranean world created by American writer Edgar Rice Burroughs (of Tarzan fame). The bones found in the cave provide hard evidence that brown bears were present on Vancouver Island at the end of the last ice age. Radiocarbon dating and DNA analysis revealed that some of those bones came from two individual brown bears that lived some 12,500 years ago.
Brown bears arrived in North America from Eurasia by crossing Beringia, the now-submerged land connecting modern-day Siberia and Alaska. Evidence suggests that, as the ice sheets retreated, brown bears ventured farther south into the continent at around the same time people did. On the shore of Calvert Island, just 63 kilometers north of Vancouver Island, recently discovered human footprints were radiocarbon dated to 13,000 years ago. Along with these newly arrived people, brown bears entered a novel and changing environment. They also encountered two other bear species that had already been living in the area for millennia.
The bones of a giant short-faced bear (Arctodus simus) were also found inside Pellucidar cave. These specimens are between 11,600 and 11,800 years old. Rearing up on their hind legs, giant short-faced bears stood twice as tall as the average man today. In addition to being North America’s largest carnivorous land mammal, they had longer legs than any bear species today and were undoubtedly the fastest bears to have ever lived, probably reaching speeds of 64 kilometers per hour, despite weighing twice as much as today’s average brown bear. Their skull and dentition suggest they were true carnivores that ate only meat, although paleontologists debate the veracity of that claim. Short-faced bears likely became extinct about 11,000 years ago. Their disappearance coincided with a changing climate; the loss of the large herbivores they preyed upon or scavenged, including horses, bison, and muskoxen; and perhaps increased competition from grizzlies.
”The short-faced bear was another bear species found in North America, but it could not weather the change following the last ice age."
The bones of a third species of bear were also found in Pellucidar cave. These specimens, dated to 11,125 years ago, belonged to an American black bear—the species that still thrives on the island today.
The fate of the brown bears of Vancouver Island remains a mystery. All we know for certain is that they were there 12,500 years ago, and then they disappeared. Bruce McLellan’s best guess is that, in the competition for food and territory, they lost to black bears and people, who have shown a greater ability to live in proximity. We may never know. But Vancouver Island still offers excellent brown bear habitat. There’s no reason it could not support a population of grizzlies today or in the future. There are many factors that would inhibit grizzlies from establishing a population on Vancouver Island, crossing a three-to 4.5 kilometer gap is one of them.
McLellan has been around long enough to witness a dramatic shift in attitudes toward grizzlies. The original “war on carnivores” waged by settlers and their descendants has evolved into a strong desire to help populations recuperate. Things really changed in 1973 with the Endangered Species Act, which proved to be a watershed in the efforts to protect grizzlies in the United States. “People started valuing them,” he says. And, in 2017, public opinion in British Columbia led the government to end the hunting of grizzlies throughout the province.
Christina Service has also seen a change in attitudes on the BC coast since her PhD work just six years ago. She’s optimistic that, in Canada’s Great Bear Rainforest at least, the future of brown bears is bright. She credits this to the investment in bear research and monitoring, First Nations rapidly incorporating this knowledge into conservation policy and coexistence strategies, and communities pivoting toward a conservation-based economy—one that values ecotourism and bear viewing.
Both biologists agree that climate change will again play a role in the future of brown bears, as it did at the end of the last ice age, but the outcome is difficult to predict. Over the next century, coastal brown bears may shift from being “salmon-driven to berry-driven,” McLellan says. This represents a fundamental change for coastal grizzlies, from a high-calorie to a lower-calorie diet, and will test their adaptability—berry-eating bears would be smaller by about half. One of McLellan’s biggest concerns regarding climate change and brown bears is that human climate refugees will look at British Columbia’s temperate coast as an attractive place to live and beat the heat in a warming world. As we expand our range, it means even more competition for space and resources.
In the Arctic, sea ice is disappearing at an accelerated pace. Brown bears will likely continue to push north as polar bears decline, making U. arctos an early winner of the climate change sweepstakes. If current trends continue, including the loss of habitat and hybridization, brown bear DNA could eventually overwhelm polar bear DNA. At that point, polar bears as we know them would disappear from the landscape, their remaining genetic material having rejoined U. arctos—the species from which they evolved.
As McLellan approaches the end of his career, the fortunes of brown bears are looking brighter than when he started. In a world of bad news for wildlife and wilderness, that’s encouraging. Brown bears are curious and have proved themselves to be highly adaptable creatures across incredibly varied landscapes. Before settlers arrived, brown bears and Indigenous peoples lived throughout the western half of North America. We know they will coexist with us. Their survival depends on our willingness to coexist with them.
Previous studies have shown that locomotion by cursorial animals over a large size range can be described as dynamically similar across all speeds (Farley et al., 1993; Alexander, 2005). Locomotion is considered to be dynamically similar if, at a given dimensionless speed (Froude number), parameters can be made identical by multiplying forces, linear dimensions and time intervals by constant factors (Alexander and Jayes, 1983). In their seminal study, Alexander and Jayes (1983) characterised cursorial animals as those that stand with the humerus and femur closer to vertical than horizontal, which excludes other morphological characteristics that are considered cursorial in other studies (described above).
Relative to cursorial species, bears appear to have substantial movement in the frontal plane during locomotion. For example, bears have an unusual carpal movement, which manifests as a medial rotation during swing (Davis, 1949; Gray, 1968; Inuzuka, 1996). Further, grizzly bears have a medially directed forefoot position during stance, relative to the direction of travel. This differs from most cursorial species, which limit movement to the frontal plane to enhance efficiency and restrict forces to the direction of travel (Liem et al., 2001). Because of this, the mediolateral forces generated by cursorial animals are comparatively small and frequently ignored in the analysis of locomotion (Budsberg et al., 1987). However, some primates walking bipedally and animals with sprawling gaits have been shown to produce mediolateral ground reaction forces equal to or greater than the magnitude of their anterior–posterior forces (Willey et al., 2004). Currently, it is unclear to what extent the forces generated by bears during locomotion are similar to or differ from those of well-studied groups of terrestrial mammals, particularly considering the angle of the forefoot during stance.
In addition to terrestrial locomotion, the forelimbs may be involved in a wide range of other activities, especially in non-predatory carnivorans that may forage for food or exhibit escape behaviours such as climbing. The requirement of predators to chase down vertebrate prey overcomes the need for dexterity upon capture; therefore, forelimb dexterity in carnivores is negatively correlated with vertebrate predation. Bears and other plantigrade carnivores (i.e. generally omnivorous species) have higher dexterity scores than digitigrade carnivorans (Iwaniuk et al., 2000). Contributing to this dexterity is the morphology of the forelimbs, such that the ulna and radius are separate in plantigrade animals, resulting in the ability to supinate and pronate (rotate the forearm to point the palm up or down). In cursorial animals, the ulna and radius are fused to increase stability and therefore speed (Liem et al., 2001). Additionally, pentadactyly is only retained in plantigrade species as loss of digits is characteristic of digitigrade and unguligrade postures; this is associated with the reduction of distal limb mass that, along with elongation of the distal limbs, increases speed in cursorial animals (Garland and Janis, 1993). The difference in forelimb bone anatomy, as well as the differences in ecology, between cursorial and plantigrade species of the Carnivora is likely to have resulted in differences in locomotion.
The overall goal of this study was to determine whether locomotion by grizzly bears differs from that of other large quadrupedal animals, which tend to be digitigrade or unguligrade. We hypothesised that the gaits used by grizzly bears would be similar to those used by smaller plantigrade animals, as opposed to similarly sized cursorial animals, because of the differences in morphology of the distal limb. Further, we predicted that the mediolateral ground reaction forces would be higher in forelimbs of bears, compared with other species, as a result of their medially directed stance. These hypotheses were addressed by examining the footfall patterns and stride parameters of grizzly bears to identify gaits, and characterising the magnitude, time-varying shape and relative distribution of three-dimensional ground reaction forces generated by the forelimbs and hindlimbs over a range of speeds.
