You’ve probably heard the argument: animal populations that have been through a major decline in numbers often have such low genetic diversity that they are extremely vulnerable to subsequent extinction.
Photo credit USGS
In an interview in late March regarding a new genetic paper on polar bear evolution (by Matt Cronin and colleagues), polar bear biologist and Polar Bears International spokesperson Steve Amstrup made a ridiculous statement: that polar bears have never experienced a rate of warming like they’ve seen over the last 30 years. I countered that easily here.
In that same interview about the Cronin et al. paper, fellow geneticist Charlotte Lindqvist offered an outdated argument against future polar bear survival that is as easy to refute as Amstrup’s “unprecedented rate of warming” nonsense.
I didn’t have time to deal with it back in April [where has the time gone?] but want to get back to it now because it’s important: there is lots of evidence to support my contention that polar bears are not more vulnerable to extinction just because they have low genetic diversity.
Posted in Conservation Status, Evolution
Tagged Amstrup, extinction, extinction risk, genetic diversity, increasing genetic diversity, Lindqvist, low genetic diversity, polar bear, population bottleneck, population size, recovery, reduced population size, threat to survival, threatened species
If I was invited by USA TODAY to discuss how climate change is affecting polar bears now – summed up in three talking points – this is what I’d say. I’d use some meaningful images rather than cute pictures of cuddly bear cubs and I’d provide links to my work with references and details to back up my answers.
Compare my responses to those supplied by Steve Amstrup in his capacity as spokesperson for Polar Bears International (“Save our sea ice!”) to Jolie Lee at USA TODAY last week, who’s word is expected to be taken as gospel.
Posted in Advocacy, Cannibalism, Polar bear attacks
Tagged Amstrup, Arviat, cannibalism, climate change, disappearing population, fasting, global warming, hibernation, human-bear conflicts, melting ice, polar bear, polar bear attacks, starving bears, Stirling
“Our results suggest that mark–recapture estimates may have been negatively biased due to limited spatial sampling. We observed large numbers of bears summering in southeastern WH, an area not regularly sampled by mark–recapture.” Stapleton et al. 2014.
Polar bear at Wapusk National Park in August 2011. Courtesy Parks Canada.
We’ve seen the results of this 2011 study before, in government report format. But now it’s been revamped, peer-reviewed and published in a respected scientific journal – it actually came out in February, without fanfare, but I’ve only just come across it.
Some excerpts below, with conclusions that should raise some eyebrows.
Posted in Conservation Status, Population, Sea ice habitat
Tagged aerial survey, early breakup, endangered, invalid methods, later-than-average breakup, mark-recapture, polar bear, population estimate, Seth Stapleton, Southern Beaufort, Southern Hudson Bay, threatened, US Fish and Wildlife Service, Wapusk National Park, western hudson bay
Satellites images might be able to replace aerial counts of polar bears in some places — if there are no clouds. But it seldom distinguishes cubs and can’t tell males from females, found a 2012 study of Foxe Basin bears that’s just been published.
Note: This is my 200th post since July 26, 2012!
Posted in Population
Tagged aerial survey, cubs, Foxe Basin, helicopter survey, polar bear, population estimates, Rowley Island, satellite images, sea ice, September ice minimum, Seth Stapleton, USGS
In the last few days, ice coverage on Western Hudson Bay finally dropped below the 30% level that now defines ‘breakup’ for polar bears: a few bears near Churchill started to come ashore late last week but most will stay on the ice until the end of July. That means breakup this year was unofficially July 8th, a week later than average (July 1) for the third year in a row.
Don’t’ tell that to the folks at Polar Bears International, though, because they’re busy telling people that the ice-free season for Western Hudson Bay bears is now longer than it was before the 1990s. What they mean is that the overall trend is toward early breakup dates.
But what they don’t admit is that over the last 44 years, breakup was a full two weeks earlier than average for Western Hudson Bay only six times and only three of those early breakups occurred within the last 13 years. See the calculations below and see what you think.
Posted in Sea ice habitat
Tagged average breakup date, breakup, Canadian Ice Service, Churchill, early breakup, ice charts, Kelsey Eliasson, late breakup, Polar Bear Provincial Park, prolonged ice-free season, Seth Cherry, Wapusk National Park, western hudson bay
Christina Wu at the Urban Times (July 3, 2014) recently asked this question. She came up with a surprisingly balanced argument but some predictable responses from IUCN Polar Bear Specialist Group (PBSG) biologists. As a consequence, she overlooked some critical facts that make a big difference to the answer.
Figure 1. Predictions of polar bear population declines by 2050 are being used by the Center for Biological Diversity, WWF and Polar Bears International to solicit donations.
Posted in Conservation Status, Population
Tagged Amstrup, Center for Biological Diversity, Chukchi Sea, computer models, endangered species, global warming, IUCN Polar Bear Specialist Group, more polar bears, PBSG, Peacock, polar bear, population increase, predictions, sea ice decline, Southern Hudson Bay, threatened with extinction, western hudson bay, York
Here is the June 2014 follow-up to my post on the July 2013 track map for female polar bears being followed by satellite in the Beaufort Sea by the US Geological Survey (USGS) – “Ten out of ten polar bears being tracked this summer in the Beaufort Sea are on the ice.”
See that post for methods and other background on this topic, and some track maps from 2012 (also available at the USGS website here).
The USGS track map for June 2004 is copied below (Fig. 1).
Compare this to May’s map (Fig. 2) – the 20 bears from last month are down to 14, and all seven of the bears outfitted with glue-on satellite transmitters in April [either males or subadult animals] have either moved out of the area or their tags have fallen off or stopped transmitting. This means that all of the bears shown on the June map below are females with satellite radio collars.
Posted in Life History, Sea ice habitat
Tagged Alaska, Beaufort Sea, Chukchi Sea, polar bear movements, polar bears, satellite collars, sea ice, Southern Beaufort, tracking polar bears, USGS