Category Archives: Life History

Declining polar bear weights and early breakup dates in WHB, Part I: What’s a starving bear?

The oft-repeated claim that polar bears are starving in Western Hudson Bay (e.g., here, here, here, and here) comes primarily from a 10 year old study that documented a declining trend in polar bear body condition (a biology euphemism for relative fatness) between 1980 and 2004, which appeared to correlate with earlier and earlier breakup dates for Hudson Bay.

Figure 1. Polar bear female with cub, 2009, Churchill, Western Hudson Bay. Wikipedia.

Figure 1. Polar bear female with cub, 2009, Churchill, Western Hudson Bay. Wikipedia.

The authors of that study (polar bear specialist Ian Stirling and NASA sea ice researcher Claire Parkinson) reported the body weights of lone female bears captured in Western Hudson Bay between 1980 and 2004. The trend over time in those bear weights was then correlated with the overall change in dates of sea ice breakup on Hudson Bay for that period.

However, it turns out that while the trend of body condition and the trend in breakup dates indeed correlated over time, the actual year to year data did not. The question is, what does that mean for the claim that polar bears in WHB are starving?
Continue reading

Mass haulouts of female Pacific walrus as a sign of population health

Mass haulouts of female Pacific walrus and their calves in fall don’t happen all the time but they do occur. I recently pointed out (here and here) two instances of such incidents from the 1970s.

I said this provided evidence that the September 2014 incident reported in the media was not “a new phenomenon” for this region, as WWF spokepersons and Alaskan biologists have claimed (reiterated in this PBS interview).

Figure 1. Walrus females and calves hauled out on a beach in Svalbard, photo accompanying an October 6, 2014 news report in “Eye on the Arctic” of the rapidly increasing Atlantic walrus population there.   (Photo: Thomas Nilsen/Barents Observer).

Figure 1. Walrus females and calves hauled out on a beach in Svalbard, photo accompanying an October 6, 2014 news report in “Eye on the Arctic” of the rapidly increasing Atlantic walrus population there. (Photo: Thomas Nilsen, Barents Observer).

One aspect of the recent occurrence of a large herd on an Alaskan beach that apparently needs reiterating is that the population of walruses declined rather markedly after a 1970s peak and has rebounded since. This suggests that huge herds of females and calves hauling out on beaches in the fall to feed might only be seen when the population is very large.
Continue reading

Mass gatherings of walrus follow-up – sea ice maps for 1978 and 1972

Walruses as polar bear prey and sea ice were on my mind last night and I remembered that we DO have detailed sea ice information for 1978 and 1972 – from the sea ice atlas put together by University of Alaska Fairbanks (UAF), which has ice concentration maps for Alaska going back to 1850 — and for every year up to 2013 (reported previously here).

Chukchi Sea walrus, June 2014. US Fish and Wildlife Service.

Chukchi Sea walrus, June 2014. US Fish and Wildlife Service.

I’ve copied some of the ice maps below.

It is clear that ice was available close to Wrangel Island in 1972 when walruses chose to haul out on the island in huge numbers. And in 1978, there was ice present to the north of the walrus herd, but they had moved away from the ice to get to St. Lawrence Island, where they hauled out in large numbers.

This means it is more likely that food resources were the issue, not sea ice.
UPDATE OCTOBER 3 2014:

See another interesting follow-up elsewhere: Walrus inconsistencies
Continue reading

Journalists still pushing the “polar bears eat snow geese story,” as if it matters

I wrote about this issue in January (January – and journalists are still pushing it).

Courtesy NY Times, Sept. 22 2014.

Figure 1. Courtesy NY Times, Sept. 22 2014. Click to enlarge.

This month, the New York Times (September 22, 2014 James Gorman, “For Polar Bears, a Climate Change Twist”) is pushing it big-time (and so it’s been picked up elsewhere, like by the Anchorage Daily News).

Myths and misinformation about this phenomenon dispelled below.
Continue reading

Ian Stirling now says the polar bear that “died of climate change” last year was “in his prime”

With Barents Sea ice way above average this summer, Polar Bear Specialist Group biologist Ian Stirling now claims the old polar bear that he said died of climate change last year on Svalbard was “in his prime” and still blames the bear’s death on lack of sea ice — despite all evidence to the contrary.

UPDATE Sept. 19, 2014 typo fixed in Fig. 1 caption [sea ice low for 2012 was 3.41 m2km, not 4.1, see here.]

Figure 1. The National Snow and Ice Data Center (NSIDC) says the September minimum for 2014 is “imminent” and suggests the low may come in at 5.1 million square kilometers (far short of the 4.1 m2km low reached in 2012. About the much larger than average amount of ice around Svalbard and Franz Josef Land, they said only: “As was the case for the beginning of the month, extent remains below average in all sectors of the Arctic except for a region in the Barents Sea, east of Svalbard.”

Figure 1. The National Snow and Ice Data Center (NSIDC) says the September minimum for 2014 is “imminent” and suggests the low may come in at 5.1 million square kilometers (far short of the 4.1 3.41 m2km low reached in 2012. About the much larger than average amount of ice around Svalbard and Franz Josef Land, they said only: “As was the case for the beginning of the month, extent remains below average in all sectors of the Arctic except for a region in the Barents Sea, east of Svalbard.”

Continue reading

Summer sea ice melt and polar bear maternity dens

The yearly sea ice minimum extent is almost upon us, which has recently been the seasonal signal for excitable biologists and their activist groupies to resume their breathless rants about what sea ice loss could mean for polar bears.

Polar bear den_CreditUSFWS_labeled

Never mind that the summer minimum extent reached in September, no matter how low it goes, is pretty much irrelevant to polar bear health and survival. As I’ve discussed before, what’s really important is the presence of not-too-thick ice during the spring, so they can catch lots of young seals and put on lots of fat.

But to a lesser degree, the extent at mid-to-late summer is important because this is when pregnant females that prefer to make their maternity dens on shore are looking for good places to spend the winter.

So the topic for today is this: how much does the extent of ice at the height of summer dictate where polar bear females make their winter dens?
Continue reading

Bearded seals in Alaska face no serious threat of reduction, let alone extinction, judge rules

Here’s a significant turn of events involving a story I reported on earlier: a US District Court judge ruled on Friday 25 July 2014 that the Bering/Chukchi Sea population of bearded seal (Erignatha barbatus) was improperly given ‘threatened’ species status in 2012. Judge Beistline ordered the National Marine Fisheries Service (NMFS) to correct deficiencies in its study of the population.

Bearded seals are important secondary prey species for polar bears in some regions of the Arctic (Thiemann et al. 2008), after ringed seals (which were also listed as ‘threatened’ in 2012).

beardedseal-mspindler-usfws

Among other points made in his written decision, the judge is quoted as saying (reported here):

“A listing under the ESA based upon speculation, that provides no additional action intended to preserve the continued existence of the listed species, is inherently arbitrary and capricious.” [my emphasis]

Arbitrary and capricious — now that’s a slap-down. He also reportedly called the ESA listing “an abuse of discretion.”

The question is, how often have other ESA listings – not challenged in court – been based on similarly arbitrary and capricious decisions that also involved an abuse of discretion?

More quotes from Judge Beistline’s decision, and reaction to it, below.
Continue reading