Tag Archives: pizzly

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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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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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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Another alleged grizzly-polar bear hybrid shot but it’s not a sign of climate change

CBC News this morning (“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“) suggests that a putative grizzly x polar bear hybrid bear shot outside Arviat in Western Hudson Bay is a sign of climate change, based on an interview with a black bear expert from Minnesota.

Hybrid pb shot in Arviat_CBC 18 May 2016

This bogus claim has been busted so many times it’s a wonder it still arises – even polar bear specialist Ian Stirling has said flat out that such hybrids are not due to climate change. On top of that, some of the details regarding this putative hybrid make me want to wait for confirmation from DNA testing before adding it to the roster of known hybrids.
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