OutdoorWriter
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More 'garbage' from FB....Also, be sure to view the new elk one I posted in the Give 'em Room thread today.
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Don't Mess with Mama
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OutdoorWriter
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OutdoorWriter
Long Time Member
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OutdoorWriter
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Why do bears rub their backs against trees?
Adult male grizzly bears use so-called "rub trees" as a way to communicate with each other while looking for breeding females, and that this behaviour could help reduce battles between the bears.
Ecologists have at last got to the bottom of why bears rub trees – and it's not because they have itchy backs. Speaking at the British Ecological Society's Annual Meeting in Glasgow the week of September 10, Dr Owen Nevin of the University of Cumbria will reveal that adult male grizzly bears use so-called “rub trees” as a way to communicate with each other while looking for breeding females, and that this behaviour could help reduce battles between the bears.
Many theories have been advanced as to why bears rub trees: some thought females might rub trees as they came into oestrous, and others that bears might be giving their backs a good scratch to get rid of parasites or pick up sap to act as insect repellent. Until now these ideas have been extremely difficult to test because bears usually live at low densities and rubbing is relatively rare behaviour.
Because bears use the same rub trees for generations, and because he has logged rub trees over almost a decade working on bears in British Columbia in Canada, Nevin has been able to gain a unique insight into grizzlies' behaviour. Over the past two years, he used four digital cameras with infra-red trips set up opposite rub trees to collect data on which bears used the trees and when. He coupled this with satellite telemetry equipment to track individual bears' movements.
“The cameras show that adult male bears are the most likely to rub trees, and the satellite telemetry tells us that males move from valley to valley in large loops, marking trees as they go, while looking for breeding females,” Nevin says.
Nevin believes that by marking trees, adult males may be getting to know each other better, and that this scent familiarity could act as a way of reducing fighting among adult male bears. According to Nevin: “Big male bears can seriously injure and even kill each other when they get into a fight. If one recognises the other from the scent marks on the rub trees in the area he knows he’s in for a tough fight - he’s on the other guy’s patch so to speak - so it might be better to back away than make a serious challenge.”
Like other species, male bears will sometimes kill a female’s offspring to get a chance to mate with her; scientists refer to this as sexually-selected infanticide. Nevin’s work suggests that very young bears may be using the rub trees to help them trick potentially killer males.
“It’s really hard to document, but on several occasions the cameras caught cubs who are being chased away from their mother by a large male visiting and rubbing on trees which he has marked. They can visit the tree two or three times in a day, sometimes within an hour of the big male, so it may be that smelling like him makes them safer – related animals smell similar and animals are less aggressive towards relatives,” Nevin says.
As well as improving our understanding of how bears communicate, the results should also help improve bear conservation by affording an insight into the behaviour of secretive male bears. Earlier work in Canada and Alaska has shown that tourist activities can change how adult male bears behave during the autumn salmon-feeding season, which has been the focus of eco-tourism, but spring viewing when the bears are breeding is becoming increasingly popular.
According to Nevin: “Understanding normal behaviour has to be the starting point for managing bear populations and our activities around them. It doesn’t matter whether we’re considering impacts of tourism or sport hunting on these dense North American populations or reintroductions and enhancements in threatened European populations: knowing how these animals interact with each other will help us to make the right decisions.”
Adult male grizzly bears use so-called "rub trees" as a way to communicate with each other while looking for breeding females, and that this behaviour could help reduce battles between the bears.
Ecologists have at last got to the bottom of why bears rub trees – and it's not because they have itchy backs. Speaking at the British Ecological Society's Annual Meeting in Glasgow the week of September 10, Dr Owen Nevin of the University of Cumbria will reveal that adult male grizzly bears use so-called “rub trees” as a way to communicate with each other while looking for breeding females, and that this behaviour could help reduce battles between the bears.
Many theories have been advanced as to why bears rub trees: some thought females might rub trees as they came into oestrous, and others that bears might be giving their backs a good scratch to get rid of parasites or pick up sap to act as insect repellent. Until now these ideas have been extremely difficult to test because bears usually live at low densities and rubbing is relatively rare behaviour.
Because bears use the same rub trees for generations, and because he has logged rub trees over almost a decade working on bears in British Columbia in Canada, Nevin has been able to gain a unique insight into grizzlies' behaviour. Over the past two years, he used four digital cameras with infra-red trips set up opposite rub trees to collect data on which bears used the trees and when. He coupled this with satellite telemetry equipment to track individual bears' movements.
“The cameras show that adult male bears are the most likely to rub trees, and the satellite telemetry tells us that males move from valley to valley in large loops, marking trees as they go, while looking for breeding females,” Nevin says.
Nevin believes that by marking trees, adult males may be getting to know each other better, and that this scent familiarity could act as a way of reducing fighting among adult male bears. According to Nevin: “Big male bears can seriously injure and even kill each other when they get into a fight. If one recognises the other from the scent marks on the rub trees in the area he knows he’s in for a tough fight - he’s on the other guy’s patch so to speak - so it might be better to back away than make a serious challenge.”
Like other species, male bears will sometimes kill a female’s offspring to get a chance to mate with her; scientists refer to this as sexually-selected infanticide. Nevin’s work suggests that very young bears may be using the rub trees to help them trick potentially killer males.
“It’s really hard to document, but on several occasions the cameras caught cubs who are being chased away from their mother by a large male visiting and rubbing on trees which he has marked. They can visit the tree two or three times in a day, sometimes within an hour of the big male, so it may be that smelling like him makes them safer – related animals smell similar and animals are less aggressive towards relatives,” Nevin says.
As well as improving our understanding of how bears communicate, the results should also help improve bear conservation by affording an insight into the behaviour of secretive male bears. Earlier work in Canada and Alaska has shown that tourist activities can change how adult male bears behave during the autumn salmon-feeding season, which has been the focus of eco-tourism, but spring viewing when the bears are breeding is becoming increasingly popular.
According to Nevin: “Understanding normal behaviour has to be the starting point for managing bear populations and our activities around them. It doesn’t matter whether we’re considering impacts of tourism or sport hunting on these dense North American populations or reintroductions and enhancements in threatened European populations: knowing how these animals interact with each other will help us to make the right decisions.”
OutdoorWriter
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You never know how they identify in today's world. Might even share unisex restrooms.
Here's more:
***************
In bear country, it’s not uncommon to notice the evidence of a bear rubbing against a tree, even if you don’t catch it in the act. Claw marks may be etched in the bark. Hair may get left behind.
“With more people using camera traps and video cameras on camera traps, it became pretty obvious that this is a major behavior that bears do,” said Mark Boyce, a professor of ecology at the University of Alberta and a TWS member. Some video has even captured bears getting really into it, bouncing their behinds on the ground and rubbing their backs up and down.
Researchers took advantage of this behavior to help them collect bear hair samples and analyze their DNA. Past research used barbed wire and stinky bait to attract bears and collect hair from the wire in order to analyze DNA. Researchers could use that DNA to identify individuals and estimate abundance. But Boyce and his team wanted to collect DNA from hair samples left at these rub trees.
Boyce and his colleagues, including lead author Andrea Morehouse, who was his graduate student at the time, wondered if there was a fitness benefit to this behavior. “Everybody always wondered why bears do this rubbing thing,” he said. “You might just think they have an itch, and they’re scratching their backs.”
Luckily, in southwestern Alberta, researchers already had been collecting DNA data on grizzly bears (Ursus arctos horribilis) using these methods for some time. “So we built a pedigree because knew which bears were related to which bears and which were offspring,” he said.
In a study published in PLOS ONE, the team used this information to determine which individuals were showing up at various rub sites, but they also could tell other information about where those individuals showed up on the family tree.
They found that the grizzlies that rubbed more also had more reproductive success — more mates and more offspring. “There was a clear result that there was a fitness advantage to rubbing,” Boyce said. “One of the interesting things is that this occurs for both males and females.”
This likely has to do with scent marking, he said. It could be that the bears are communicating their condition, dominance or their sex. “If you’re a female with cubs, you might smell a male and want to bugger off and get out of there,” he said. “Alternatively, if you’re in heat, you might want to go find them.”
The results suggest that both male and female grizzlies with more vigor might rub more because they are better able reproduce. It isn’t clear what the mechanism is, Boyce said, but it is clear that they are using olfactory communication through these rubs.
The research reveals new findings about grizzlies’ natural history that people know little about. If rubbing behavior varies among bears, such variation might create a bias when using tree-rubbing data to estimate populations, Boyce said. “Knowing more about the behavior and what motivates it could help us better use that information for estimation of abundance,” he said.
feddoc
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OutdoorWriter
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I'm not sure what the correlation might be, but in the area of BC where I hunted bear a few times, many of them have spots somewhere on their bodies that are completely devoid of any hair. Since all the hunts were in the spring right after they come out of hibernation, it always seemed a bit strange to me.
I've been fortunate that all the ones I've killed have had really super hides. In contrast, when I brought my son along in 2005 he killed a boar with about a 1' square bare patch on one side -- the opposite side we couldn't see when he pulled the trigger. Taxidermist Marc Plunkett did an excellent job of adding some extra hide into the spot for a rug.
I've been fortunate that all the ones I've killed have had really super hides. In contrast, when I brought my son along in 2005 he killed a boar with about a 1' square bare patch on one side -- the opposite side we couldn't see when he pulled the trigger. Taxidermist Marc Plunkett did an excellent job of adding some extra hide into the spot for a rug.
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OutdoorWriter
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That video makes the purpose of the tree rubbing pretty obvious.
