There is a world somewhere between reality and fiction. Although ignored by many, it is very real and so are those living in it. This forum is about the natural world. Here, wild animals will be heard and respected. The forum offers a glimpse into an unknown world as well as a room with a view on the present and the future. Anyone able to speak on behalf of those living in the emerald forest and the deep blue sea is invited to join.
--- Peter Broekhuijsen ---

  • 1 Vote(s) - 5 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Grolar Bears

India brotherbear Offline
Grizzly Enthusiast
#1
( This post was last modified: 05-24-2016, 10:39 AM by brotherbear )

BARROW, Alaska -- Most Alaskans and Canadians have a bear story - tales of fearsome grizzlies, even polar bears. But a mix of the two?
They're known as pizzlies or grolars, and they're a fusion of the Arctic white bear and their brown cousins. It's a blend that's been turning up more and more in parts of Alaska and Western Canada.
Bears sharing both species' DNA have been recorded several times over the past decade. So why are these two species linking up?
It's called flexible mate choice: The bears are mating with the best possible partners as opposed to not mating at all, and they're mating because they share relatively close territories and the same branches of the same evolutionary tree.
Intraspecies mixing between the two happened thousands of years ago, thanks to the advance and retreat of glaciers, and of late, it has been boosted by climate change. Scientists say it's also probably been assisted by policies that protect both bears from culling and hunting, affording further opportunities for mingling.
The crossbreeds found in Alaska and Canada are not genetic anomalies. Scientists have found the mix in the islands off Southeast Alaska, where bears resemble grizzlies but contain polar bear DNA. That indicates decades of sporadic interbreeding, said Steven Amstrup, chief scientist at Polar Bears International.

The polar-grizzly cocktail is also far from the only recent animal hybrid. The coywolf - a coyote-dog-wolf amalgamation - and a lynx-bobcat mix have been popping up along the northern Atlantic coast. The more scientists analyze species' genomes, the more they realize that animals we label as "pure breeds" actually share DNA - and that includes us.

Many humans carry traces of DNA from Neanderthals, which means we're all hybrids. It also means there's no such thing as genetic purity. The concept is a romantic construct, an anthropomorphized take on nature. And what may be most surprising about this, researchers say, is the role interbreeding plays in the futures of endangered species - or, as the case may be with polar bears, accelerating their end.
Amstrup has studied bears in the Arctic since the 1970s and was instrumental in helping list the polar bear as a threatened species in 2008. He, like other experts, characterizes this "new" bear relationship as more beneficial to grizzlies than polar bears. That's because there are more grizzlies than polar bears and because grizzly territory is expanding while polar bear territory is contracting. What that adds up to is a good chance grizzlies could essentially dilute the polar bear population until it doesn't exist at all, they say.
Polar bears are getting the short end of the stick in this relationship, not "gaining any genetic diversity," said Geoff York, who led research on polar bears at the World Wildlife Fund for almost a decade before joining Amstrup at PBI.

Andrew Derocher, a professor of biological studies at the University of Alberta, has spent three decades studying bears throughout the Arctic. He, too, has a sobering view about where the hybridization is heading.



"I hate to say it, but from a genetic perspective, it's quite likely grizzly bears will eat polar bears up, genetically," he told me. And he says the changes are already at play.

All hybrids that have been analyzed had grizzly fathers, because grizzly males roam to establish territory and come in contact with receptive female polar bears. Female grizzlies tend not to stray far from their home ranges, and male polar bears don't usually creep into grizzly habitats.
Polar bears need the ice - that's where the seals and walruses they eat live. They don't hibernate, and they don't travel south of the tundra. Grizzlies, historically, rarely ventured north of the treeline. Permafrost is too cold for their liking, and they sink into the snow easily. (Polar bears have padded paws that act as snowshoes). Hunting is more challenging in the north, where prey is scarce. They're not really swimmers. 
But shifts are afoot.

"What we're starting to see in the Canadian Arctic is three-fourth grizzlies," Derocher said, referring to the offspring of 50-50 hybrids that then mated with grizzlies. "How do they act? Probably more like grizzly bears, living on land. As climate change continues, terrestrial habitat is going to increase, and the likelihood is the habitat for grizzlies, a terrestrial bear, is going to get better. That means a longer warming period and greater food potential."

Derocher said it will not be long before we start seeing female grizzlies bump into male polar bears, further straining the polar bear's genetic variation. "I suspect at the same time that that's occurring, we'll start to see polar bears on their way out."

When will that be? Impossible to say, but some experts think that as the Arctic continues warming, it may be only a few decades, perhaps a century. There are about 20,000 to 25,000 polar bears in the Circumpolar Arctic, and "an order of magnitude higher for grizzlies in that area" and other brown bears, Derocher said. "It shouldn't be a big surprise that grizzlies are moving north - everything is."
Right now, polar bears are also threatened by polychlorinated biphenyls, or PCBs, and other toxic pollution - primarily from eating seals and other animals affected by these carcinogens - that has been linked to brain damage, even causing some bears' baculums, or penis bones, to break off. 
And those outcomes could affect polar-grizzly hybrids as badly as pure breeds. No matter what bear ends up as the Arctic's future apex predator, scientists say, if the issues up north aren't solved, it won't matter what bears are there.

Hybrids are "a normal part of the evolutionary process," Derocher said. But if the ice disappears, "we won't have grizzlies or polar bears in this area. If you roll the clock ahead another number of decades or a century, quite clearly it's going to be no bears eventually." 

                                  
*This image is copyright of its original author

http://www.adn.com/wildlife/2016/5/23/lo...ow-mating/
7 users Like brotherbear's post
Reply

India brotherbear Offline
Grizzly Enthusiast
#2

*With the cubs being raised by their polar bear mothers, I am amazed that any of them survive the ordeal. I have to wonder how many there might have been that did not survive into adults. 
Reply

Australia GreenGrolar Offline
Regular Member
***
#3
( This post was last modified: 09-30-2019, 11:46 AM by GreenGrolar )

Brown bears are very successful in raising their cubs in comparison to most animals and so are polar bears in general. More cubs survive till adulthood. The grolar bear cubs only biggest threat would be a male polar bear or even a male barren ground grizzly.
Assuming that the grolar cubs have successfully survived to adulthood, there are going to be three types of bears in the tundra: polar, grolar, and grizzly.
https://greennature.proboards.com/

GreenEarthBirds - a forum focused on birds.
Reply






Users browsing this thread:
1 Guest(s)

About Us
Go Social     Subscribe  

Welcome to WILDFACT forum, a website that focuses on sharing the joy that wildlife has on offer. We welcome all wildlife lovers to join us in sharing that joy. As a member you can share your research, knowledge and experience on animals with the community.
wildfact.com is intended to serve as an online resource for wildlife lovers of all skill levels from beginners to professionals and from all fields that belong to wildlife anyhow. Our focus area is wild animals from all over world. Content generated here will help showcase the work of wildlife experts and lovers to the world. We believe by the help of your informative article and content we will succeed to educate the world, how these beautiful animals are important to survival of all man kind.
Many thanks for visiting wildfact.com. We hope you will keep visiting wildfact regularly and will refer other members who have passion for wildlife.

Forum software by © MyBB