Category Archives: Hybridization

Grizzlies vs. grizzly X polar bear hybrids by appearance alone: a photo essay

Hybridization with grizzlies comes up repeatedly in genetic studies that aim to zero in on polar bear origins and is one of the issues I explore in detail in my upcoming new book, Polar Bear Evolution: A Model for How New Species Arise. Here is a photo essay to get you thinking about grizzly X polar bear hybrids, because understanding the topic is critical to unravelling the genetic evidence on how polar bears came to be.

For example, who can forget the hoopla over the bear shot near Arviat on the shore of Western Hudson Bay in 2016 (shown above) that everyone, including polar bear expert Ian Stirling, decided must be a hybrid–but it turned out to be a blonde grizzly.

Explaining all the ins and outs of why hybrids are important to polar bear evolution is an important part of my book.

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Grizzly on the shore of W. Hudson Bay and two tagged polar bears still on sea ice at 17 August

A tundra grizzly was again caught on the live cam set up for polar bears last week (15 August) but was too late for interspecies hankypanky, even as some polar bears lingered on invisible offshore sea ice.

A polar bear rests on the ice Aug. 23, 2009, after following the Coast Guard Cutter Healy for nearly an hour in the Beaufort Sea.

Polar bear specialist Andrew Derocher reported that two of his 23 tagged polar bears were still on the sea ice, a phenomenon that’s been happening since at least 2015 at breakup. Instead of heading to shore when the sea ice concentration dwindles below 50% coverage, some bears are choosing to lounge around on decaying bits of ice, sometimes into late July or well into August, until they must finally swim ashore. There is no evidence that the bears continue to successfully hunt seals under these conditions but no evidence either that their choice to stay on the ice rather than move to land at this time of year has had any negative impact on their health or survival.

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Polar bear evolution and recent genetic papers

Two scientific papers in June on polar bear evolution got a bit of media attention but not what the topic deserves. I’ve not written about them because I am currently working on a larger piece putting this conflicting genetic information into full context. Have patience, it’s coming.

Grizzly spotted on Western Hudson Bay shore but there are no polar bears on land for it to mate with

On 28 May last week a big grizzly (probably a male) was spotted on the shore of Wapusk National Park just south of Churchill, Manitoba but unless he heads out onto the sea ice, he has no chance of finding a polar bear female to mate with. Even if he does, he is unlikely to find a polar bear female willing to mate: most polar bears mate late March to early May (Smith and Aars 2015). Brown bears (called grizzlies across most of North America) mate later in the year, from late May to July, which means finding hybrids here is highly unlikely.

A few tundra grizzlies from the Northwest Territories have been spotted moving southeast into the Hudson Bay area since 2008. There was some media-and-expert-generated excitement back in 2016 when a hunter shot what he thought might have been a grizzly/polar bear hybrid near Arviat but it turned out to be a blonde grizzly, which are not uncommon in the tundra population from which it came. A similar result came from recent genetic study: samples from two pale blonde grizzlies from the North Slope of Alaska that looked remarkably like polar bear hybrids were not only unrelated to each other but showed no evidence of being hybrids (Lan et al. 2016 Supplementary data, pg. 3).

Contrary to some predictions, grizzly/polar bear hybrids are still quite rare (Crockford 2018:23).

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New Scientist prints a more reasoned polar bear article but myths persist

New Scientist has an article coming out next week takes a fairly reasoned approach to the polar bear conservation issue. It acknowledges that polar bear numbers have not declined in recent years even though summer sea ice dropped dramatically but goes on to perpetuate a number of myths that might not have happened if the author had done his homework or quizzed his other experts as thoroughly as he did me.

New Scientist headline_10 Feb 2018 issue 3164 photo

The survivors: is climate change really killing polar bears? Rapid global warming is said to be ringing the death knell for polar bears, by melthing their icy hunting grounds. But the reality is more complex. Fred Pearce, New Scientist 10 February 2018. Online now.

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New genetics paper is not about whether climate change causes polar bear hybrids

A new paper on the evolutionary history of bears (Bears breed across species borders: Kumar et al. 2017) has concluded that hybridization is common and natural among all species of ursids. And while some media outlets (e.g. DailyMail) have framed this as surprisingly convincing proof that experts were wrong to claim that climate change is the cause of recent polar bear X grizzly hybrids, definitive evidence against that interpretation has been available for years to anyone who bothered to look: see my recent “Five facts that challenge hybridization nonsense.”

This genetic evidence is just a cherry on top of the rest but will help get the paper the media attention the authors crave.

Polar bear X grizzly hybrids were known long before climate change and sea ice decline became an issue. See also previous posts here, here, and here. In fact, as I’ve pointed out, “most polar bear hybrids said to exist have not been confirmed by DNA testing” (including virtually all of the bears specialist Andrew Derocher claimed were hybrids, including the latest one from 2016 that prompted such gems as “Love in the time of climate change”).

pizzly_andrewderocher_300dpi_2017 paper

A polar bear X grizzly hybrid, see Kumar et al. 2017. Photo by A. Derocher.

In my opinion, the most important conclusion of this paper is that occasional but widespread hybridization among bears is why it has been so hard to say with confidence when polar bears arose (which I addressed years ago, in my Polar bear evolution series: Part 1, Part 2, and Part 3). You cannot use traditional methods of pinpointing the timing of speciation events from genetic data if one or more of the species have hybridized (traded genes). See the long, fuzzy “divergence times” for bears in the image below from the Kumar paper.

Kumar et al 2017 hybridization in bear evolution_fig 5

From Kumar et al. 2017, Fig. 5: “The scale bar shows divergence times in million years and 95% confidence intervals for divergence times [speciation events] are shown as shadings.”

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BREAKING: DNA results prove so-called polar bear hybrid was a blonde grizzly

All the hubris last month about polar bear x grizzly hybrids, based on an unusual-looking bear killed near Arviat, has turned out to be wishful thinking by those who’d like to blame everything to do with polar bears on climate change. An awful lot of “experts” now have egg on their faces. That “hybrid” was just a blonde grizzly, as I warned it might.

grizzly-polar-bear-hybrid_Arviat 2016 Didji Ishalook

According to one report, Nunavut wildlife manager Mathieu Dumond said:

“Some otherwise pretty renown bear biologists jumped on the hybrid bear story without even knowing what they were talking about,” Dumond said.

“I think it was something blown out of proportion, with the wrong information to start.”

Gee, ya think? CBC ran a story too. But the CBC don’t really admit (see below) that they were the first out of the gate on this story and started the media madness. It was the CBC that relied on the opinion of a black bear expert from Minnesota (who likely only saw a picture) – but since he was willing to say it was a hybrid and that its presence was a sign of climate change, they went with it.  See “Grolar or pizzly? Experts say rare grizzly-polar bear hybrid shot in Nunavut: Expert says interbreeding may be happening more frequently due to climate change” (CBC 18 May 2016).

For background, see these recent posts on this putative hybrid and the issues on hybridization it spawned:
Another alleged grizzly-polar bear hybrid shot but it’s not a sign of climate change

Polar bear hybrid update: samples sent for DNA testing to rule out blonde grizzly

Five facts that challenge polar bear hybridization nonsense

Most polar bear hybrids said to exist have not been confirmed by DNA testing

Blonde grizzlies, like the one pictured below (which I posted the day the story broke), are actually a proven sign of natural variation within species – a critical lesson in biology that should be the take-home message here. [ADDED: 2007 Alaska Fish & Wildlife Service Newsletter article on colour variation in black and brown/grizzly bears. h/t Wayne D]

“Paging Professor Derocher”: PBSG biologist and University of Alberta professor Andrew Derocher gave so many interviews to the media on this issue I lost count – he fed the media frenzy almost single-handedly. Well, except for granddaddy of polar bear experts Ian Stirling, who said (via the Toronto Star)[update: Toronto Star published correction]:

“I think it’s 99 per cent sure that it’s going to turn out to be a hybrid,” said Ian Stirling, an emeritus research scientist with Environment Canada and adjunct professor at the University of Alberta.”

 

Grizzly light_NPS photo

Quotes from today’s story below.
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Most polar bear hybrids said to exist have not been confirmed by DNA testing

Although there are only two confirmed polar bear X grizzly hybrids (see recent posts here and here) – one in 2006 and a 2nd generation back cross in 2010 – there have been a few other unconfirmed sightings and/or hunters reports in addition to the Arviat animal shot last week, but how many?

Hybrid sightings Victoria Island spring 2012 Jodie Pongracz_GNWT

In a CBC radio interview today (27 May 2016), polar bear biologist Andrew Derocher claimed there have now been 9 polar bear/grizzly hybrids reported in Canada (with the Arviat animal shot last week being the 9th).

I think I’ve tracked down the details on those six unconfirmed Canadian sightings, plus another from Alaska. But as you will see, some of the reports are so vague it’s hard to know whether these are the animals Derocher counts as hybrids or not.
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Polar bear hybrid update: samples sent for DNA testing to rule out blonde grizzly

That putative polar bear hybrid shot in Arviat last week has been sent for DNA testing.

hybrid-bear_didji-ishalook-15 May2016_facebook

Just out from NunatsiaqOnline (24 May 2016): Nunavut biologist sends possible “grolar” bear DNA for analysis: Unusual bear killed in Arviat could just be a blonde grizzly bear

Additional details confirm the animal shot was a female, which could account for the fact it was described as “small”. The Nunavut biologist who sent in the sample for testing warned it could also be a blonde grizzly, as I pointed out last week.

UPDATE 24 May 2016: Comments added below from a Toronto Star news report below on the hybrid identity of this animal.

UPDATE 28 May 2016: See this 27 May 2016 follow-up post (Most polar bear hybrids said to exist have not been confirmed by DNA testing) for details on unconfirmed sightings or reports of hybrids.
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Five facts that challenge polar bear hybridization nonsense

It was inevitable, I suppose, that the putative hybrid shot in Arviat, Nunavut last week (see my post here) would initiate the global warming blame game.

Hybrids again_Washington Post 23 May 2016_title screencap

Washington Post, 23 May 2016, Adam Popescu: “Love in the time of climate change: Grizzlies and polar bears are now mating

Here are the five points you need to know about polar bear hybridization, as there are several nonsense statements contained in this Washington Post article.

UPDATE 24 May 2016: References adding below regarding grizzly sightings south of Churchill on the west coast of Hudson Bay (H/T Doug Clark).

UPDATE 28 May 2016: See this 27 May 2016 follow-up post (Most polar bear hybrids said to exist have not been confirmed by DNA testing) for details on unconfirmed sightings or reports of hybrids.

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