Category Archives: Life History

Polar bears move around as sea ice habitat changes – this is what resilience looks like

Oddly, it seems some people expect polar bears to sit around and suffer (or die) when local conditions deteriorate, rather than move elsewhere.

PolarBear_2008_USGS

While there are perhaps a few places where moving is not really an option over the short term, over the long term (more than one season) polar bears are free to shift to another locale if ice conditions change (either too much ice or too little).

An announcement by the WWF last week (10 April) caught my eye, as it talked about bears moving from one area to another because of changing ice conditions — as if this was surprising, extraordinary and newsworthy. That said, at least they weren’t suggesting the bears are all going to die because of declining ice, which is a huge improvement.

See what you think of this part of the press release (below), in the context of what we know about the movement of bears between regions:

Continue reading

Barents Sea polar bear condition varies with AMO and spring sea ice conditions

Fig. 1. NSIDC sea ice extent at March 8, 2014 (a "MASIE" product), with labels added. Click to enlarge.

Figure 1. NSIDC sea ice extent at March 8, 2014 (a “MASIE” product), with labels added. Click to enlarge.

In its end of February report, the US National Snow and Ice Data Center (NSIDC) noted that Barents Sea ice was below average for this time of year (see Fig. 1 above, and Fig. 5 below) but suggested this was primarily due to natural variation driven by the Atlantic Multidecadal Oscillation (AMO):

“The Barents Sea has experienced consistently low extents, particularly in winter, and this year has been no different. While the Barents and Kara seas normally have close to 2 million square kilometers (772,000 square miles) of ice in February, recent years have seen 500,000 square kilometers (193,000 square miles) of ice extent or lower. This year, the Kara Sea is near average, but the Barents Sea remains low (Figure 4a). Unlike other regions in the Arctic, longer records of Barents Sea ice extent exist from records of fishing, whaling, and other activities. A recent paper (Miles et al., 2013 [2014, now in print]) examined these records, along with paleoproxy data, to examine extent over the past four hundred years. They found a 60- to 90-year cycle in Barents and Greenland seas ice extent related to the Atlantic Multidecadal Oscillation (AMO); the AMO is a basin-wide cycle of sea surface temperature variability similar to the El Niño and La Niña cycles in the Pacific, but varying over much longer periods. This research shows that in addition to the warming trend in the Arctic, some sea ice regions are likely also responding to natural climate variability.” [my bold]

The paper they cite (Miles et al. 2014, discussed elsewhere in December 2013 here) described the AMO this way:

“The AMO is a coherent pattern of basin-wide sea surface temperature (SST) variations with a period of roughly 60–90 years. ..Paleoenvironmental studies suggest that the AMO has persisted through previous centuries [Gray et al., 2004] and even millennia [Knudsen et al., 2011].”

Note that Miles and colleagues were looking at ice records on or around the sea ice maximum in winter/spring.

The Polar Bear Twist: Norwegian biologists Jon Aars and Magnus Andersen, who I’ve discussed before, have pointed out that the condition of polar bear males and females around Svalbard (Fig. 2) they examined over the last 20 years varied with the AMO and sea ice levels in spring and early summer. [research results posted at the website for Environmental Monitoring of Svalbard and Jan Mayen (MOSJ), Norwegian Polar Institute].

Figure 1. The Barents Sea polar bear subpopulation, courtesy the IUCN Polar Bear Specialist Group. "Svalbard" is the largest archipelago, in the eastern portion.

Figure 2. The Barents Sea polar bear subpopulation boundaries, courtesy the IUCN Polar Bear Specialist Group. Svalbard is the largest archipelago, closest to the East Greenland Sea.

That makes a lot of sense to me, given that spring/early summer is the most critical feeding season for polar bears because it’s when fat young seals are most easily available.

It also makes sense to me that you may need a record hundreds of years long to understand the natural variability of Arctic Sea ice in its various regions. Recall that natural variation, not global warming, is now being used to explain the large variation in annual sea ice cover in the Bering Sea (home to Chukchi Sea polar bears). Continue reading

Tracking polar bears in the Beaufort Sea: February map

Here is the February 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 February 2014 is copied below (Fig. 1).

Continue reading

Foxe Basin aerial survey – a watershed moment for polar bear research, Part 1

While researching the population status of Foxe Basin polar bears I came across an issue that seems to have garnered relatively little attention outside the polar bear community – Inuit objections to the handling of polar bears during mark-recapture surveys and the effect of this on polar bear research in Canada.

 Figure 1. US Fish and Wildlife biologists handling a polar bear in the southern Beaufort during a fall survey, October 24, 2001. Steve Amstrup photo.


Figure 1. US Fish and Wildlife biologists handling a polar bear in the southern Beaufort during a fall survey, October 24, 2001. Steve Amstrup photo.

Foxe Basin is a large polar bear subpopulation region that encompasses the northern portion Hudson Bay into the area west of Baffin Island, see map below (courtesy IUCN Polar Bear Specialist Group).

FoxeBasin_PBSG website_Oct 2013Mark-recapture research methods routinely used by polar bear biologists became especially contentious in Foxe Basin during a population study initiated in 2007/2008, with Inuit residents voicing objections and biologists defending its practice. The following year, the mark-recapture effort was halted and an aerial survey took its place.

The aerial survey has been completed and a report on it was released in 2012 (Stapleton et al. 2012; see previous post for results) but we’ve heard very little about what happened to that mark-recapture study and why the Government of Nunavut pulled the plug on it. I plan to change that with the next couple of posts.

I’m not claiming to understand the nuances of the story because I’m only going by available documents. However, I think it’s important to shine some light on this issue since it has clearly changed the shape of polar bear research in Canada.
Continue reading

Foxe Basin polar bear status – another stable population

Foxe Basin_PBSG

Figure 1. Polar bear subpopulation regions defined by the Polar Bear Specialist Group, Foxe Basin marked.

Foxe Basin is a large subpopulation region (Fig. 1), with a total area of 1.18 million square km (Vongraven and Peacock 2011). It comprises Northern Hudson Bay and western Hudson Strait, and the area between western Baffin Island and eastern Melville Peninsula, with a large island (Southampton Island) in the middle (Figs. 2 and 3).

Figure 1. Foxe Basin polar bears subpopulation region, courtesy IUCN PBSG

Figure 1. Foxe Basin polar bears subpopulation region, courtesy IUCN PBSG

Continue reading

Thriving Foxe Basin and Davis Strait polar bears threaten nesting sea birds

UPDATE February 11, 2014. A reader (Kevin, at “Afton’s Waterfowl List”) has pointed out an error in Fig. 3, where I inadvertently labeled the bars on the upper graph as ending in 2011 instead of 2012 (the Pembroke graph ends at 2011. sigh..). I have corrected the figure and the text that refers to it, but do not believe it affects the overall conclusion. See for yourself. Thanks Kevin — and Alan for getting in touch!

Another round of press release inspired news stories emerged last week insisting that polar bear predation on ground-nesting birds during the summer ice-free period is evidence that they are nutritionally stressed by global warming.

A few weeks ago it was snow goose eggs in Western Hudson Bay – this time it’s thick-billed murre (Uria lomvia) and common eider (Somateria mollissima) eggs in Foxe Basin and Hudson Strait (e.g. see the story at Canada’s National Post and a short summary provided by Science [and it’s not even their paper!]). The source of the media attention this time is a newly-published paper by Samuel Iverson and colleagues (Iverson et al. 2014).

Figure 1. From Iverson et al. 2014 (their Fig.1), “map of the study area.” Most of the study sites are within the Foxe Basin polar bear subpopulation region (see Fig. 2 below), although the Ungava Peninsula (E), Ungava Bay (F) and Frobisher Bay (C) sites are in the Davis Strait subpopulation.

Figure 1. From Iverson et al. 2014 (their Fig.1), “map of the study area.” Most of the study sites are within the Foxe Basin polar bear subpopulation region (see Fig. 2 below), although the Ungava Peninsula (E), Ungava Bay (F) and Frobisher Bay (C) sites are in the Davis Strait subpopulation.

Polar bears have always preyed on ground-nesting sea bird and goose eggs while onshore (see Kelsey Eliasson’s take on the situation around Churchill, at his PolarBearAlley blog). The issue in this case is whether the increase in predation can be unquestionably blamed on reduced sea ice cover and nutritionally-stressed bears – that is, predation increases that correlate with year-to-year sea ice changes and bears in poor condition found consuming bird eggs.

As I did for the “polar bears eat more caribou and snow geese than they used to” press release, I refused to take the PR or the news stories at face value and went to the published paper and its supplemental data (it’s open access, see it for yourself here).

What I see in this paper is a spurious sea ice correlation and no data on the condition of the few bears observed consuming eggs. There is also no mention of the fact that polar bear numbers have increased in part of the study area (Davis Strait) or that bears in Foxe Basin and southern Davis Strait have been found to be in very good condition and reproducing well (Rode et al. 2014; Peacock et al. 2013). See my analysis below and judge for yourself.

Continue reading

Tracking polar bears in the Beaufort Sea: January map

Here is the January 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 January 2014 is copied below (Fig. 1).

Both the Southern Beaufort and the Chukchi Sea were completely ice-covered by the end of January. The seven bears tracked during November and December were reduced to five in January — down 50% from the ten bears collared in July.
Continue reading

Eat, wash up, repeat; eat, wash up, repeat…polar bears do it too!

Ah, that never-ending treadmill of meal preparation and cleanup. You might be surprised to find out that polar bears do it too.

Figure 1. How do polar bears look so clean most of the time when they get this bloody on a regular basis? They wash up! [This picture is not from Stirling’s paper].

Figure 1. How do polar bears look so clean most of the time when they get this bloody on a regular basis? They wash up!

I found an interesting description of polar bears washing during and after feeding, by a young Ian Stirling in one of his earliest published polar bear papers (Stirling 1974). At the time, he was observing polar bears on southwest Devon Island (74°43′ N; 91°10′ W, see Fig. 2 below) between 24 July and 8 August 1973. Even today, there’s ice for hunting seals in mid-to-late-summer in that part of Canada (Fig. 3).
Continue reading

Polar bear female with cubs fights off adult male – photos from W Hudson Bay

Discovery News ran a photo feature yesterday (January 28, 2014), courtesy Mike Lockhart from Polar Bears International, of an interesting incident Lockhart witnessed while was working with a government (Manitoba Conservation) research team surveying bears of Western Hudson Bay in the fall of 2013.

Figure 1. Female with 2 cubs turns on an adult male (far right) that she had been happily feeding with moments before. Mike Lockhart photo, Polar Bears International and Discovery News.

Figure 1. Female with 2 cubs turns on an adult male (far left) that she had been happily feeding with moments before. This is the 3rd photo in the sequence; see description and photo 4 below. Mike Lockhart photo, Polar Bears International, Discovery News story.

Continue reading

Churchill polar bears eat more caribou and geese now than in 1968 because there are more caribou and geese, new research reveals

The press release (pdf here) issued by the American Museum of Natural History (AMNH) a few days ago, regarding several recent papers on polar bear consumption of terrestrial foods around Churchill, Manitoba (Western Hudson Bay), left a lot to be desired in terms of relaying accurate information.

Recent research on polar bear diets by Robert Rockwell and Linda Gormezano, it says, suggests that an increase in the consumption of caribou and snow geese since 1968 is a sign that the polar bears are nutritionally stressed due to recent sea ice changes in spring (blamed on global warming) but may be adapting by changing their summer/fall diet.

As the AMNH press release puts it:

polar bears in the warming Arctic are turning to alternate food sources.”

Figure 1. Polar bear feeding on a caribou carcass, taken July 26, 2010. This photo was included in one of the papers cited in the January 2014 press release (Gormezano and Rockwell 2013:3518) and was clearly taken from the air. The caption in the paper says simply, “a polar bear looks up from the recently killed caribou it was eating,” so the bear may not have killed the caribou – some other predator (wolf or grizzly) may have made the actual kill. The dark spots on the bear appear to be flies. Credit Copyright American Museum of Natural History/ R. Rockwell.

Figure 1. Polar bear feeding on a caribou carcass, taken July 26, 2010, from the air. This photo was included in virtually all media reports and in Gormezano and Rockwell (2013a:3518, Fig. 3). The caption in the paper says, “a polar bear looks up from the recently killed caribou it was eating,” implying the bear may not have actually killed the caribou – some other predator (wolf or grizzly) may have made the kill. The dark spots on the bear appear to be flies. Credit: Copyright American Museum of Natural History/R. Rockwell.

However, the AMNH press release fails to mention – as the papers it publicizes certainly do – that Western Hudson Bay populations of caribou and snow geese have increased exponentially since a similar polar bear diet study was done in 1968/69. In other words, there were hardly any caribou or geese around back in the late 60s — little wonder polar bears weren’t eating any.

While evidence of polar bears consuming caribou and geese in recent years is certainly an “increase” over late 1960s levels, that fact says more about the status of caribou and geese populations than it does about polar bears and global warming. Media outlets that quoted the press release verbatim, as many do these days (e.g. here, here, and here), missed this essential part of the story – and of course, so did their readers.

[one story picked up the goose population increase and another revealed the caribou population increase, but none that I saw caught both]

In addition, the AMNH press release makes this erroneous statement that was picked up by every media outlet I saw except one (either exactly as written or reworded slightly):

Climate warming is reducing the availability of their ice habitat, especially in the spring when polar bears gain most of their annual fat reserves by consuming seal pups before coming ashore for the summer.” [my bold]

This is flat-out wrong: sea ice declines have been minimal in spring The earliest breakup dates since 1991 for Western Hudson Bay, where this research was done, have been mid-June (according to the most recent study by Cherry et al. 2013) and for the last few years breakup has occurred in July. Spring in the Arctic is March-May; summer is June-August. This error appears to have come from authors, Robert Rockwell and Linda Gormezano, as I show below. Is this just sloppy writing or deliberate misinformation?

Overall, the press release and resulting media reports seem to be further examples of hyping global warming at the expense of the actual science involved and I have to agree with Andrew Derocher’s interpretation of the significance of terrestrial food items for polar bears. See what you think.
Continue reading