Tag Archives: terrestrial foods

Terrestrial food fight amongst polar bear researchers reflects political differences

With a few big guns on one side and some fringe folk on the other, a dichotomy of opinion has developed amongst polar bear researchers regarding whether or not consumption of land-based foods is making a difference to polar bear survival (or is likely to in the future).

Polar bears eating terrest foods WHB_Rockwell press release

It’s been going on for a while now. Last year, two US Geological Survey members of the IUCN Polar Bear Specialist Group (PBSG) apparently got fed up with the scatter-shot of papers promoting terrestrial foods as a possible salvation for polar bears (e.g. Iles et al. 2013;  Iverson et al. 2014; Rockwell and Gormezano 2013a, 2013b). In April, they published a canon volley of a paper meant to blow all that ‘polar-bears-might-survive’ talk out of the water once and for all (Rode et al. 2015).

Note that although the PBSG didn’t bother to update their website with the IUCN Red List assessment when it came out last November, they had a link up to the USGS terrestrial feeding paper within 16 days (with an editorial summary in the “NEWS” section as well as a listing of the paper in the “RECOMMENDED READING” section). As I suggest below, this difference in treatment may not be a coincidence.

However, another group of non-PBSG researchers  haven’t given up just yet, as shown by the title chosen for the most recent news report (Alaska Dispatch News, 16 June 2016) on the just-finished International Bear Conference:

Want to know how a changing climate is affecting polar bears? Look at what they’re eating.

Apparently, Jeff Welker, a University of Alaska Anchorage researcher who is co-author on two recent papers on the subject of polar bear consumption of terrestrial foods (Tartu et al. 2016 and Rogers et al. 2015), gave a presentation at the conference that raised this topic yet again. His talk came on the heels of an earlier presentation by Todd Atwood, who suggested Southern Beaufort polar bears might benefit from staying onshore to eat left-over whale scraps instead of staying on the sea ice during the summer (even though he had no data to support that opinion – as I discussed in this post).

Here’s the question: is this dispute really about what polar bears eat or don’t eat when they’re on land – or is it symptomatic of the underlying politics of polar bears? [CBC documentary video by that name here]
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New paper shows no harm from more time on land for S. Beaufort polar bears

polarbears-arcticnatlwildliferefuge-suzannemiller-usfws_labeled_smTake-home quote from a new polar bear paper by Todd Atwood and colleagues (2016):

“…there is no causal link between the patterns in polar bear vital rates and increased use of terrestrial habitat…”

In other words, there was no information to link the increased time polar bears spent onshore with either an increase or a decrease in body condition, survival or cub production. The authors did find that polar bears were strongly attracted to the bone piles that accumulated in the fall from 2010-2013 after Inuit bowhead whale (Balaena mysticetus) hunting at Barrow, Cross Island, and Kaktovik. Isn’t that a surprise?

The results also appear to confirm previous work that showed terrestrial (land-based) foods are not important to polar bears – a conclusion I totally agree with and which I discussed last year here. No wonder there was no press release issued by USGS about this study. It’s only “news” because someone the Anchorage Daily News interviewed lead-author Atwood yesterday as a way of promoting the International Bear Conference (see previous post here, now updated with a link to the Talk of Alaska radio podcast). Atwood implied there could be advantages to bears from feeding on the bone piles but admitted he had no data to support that assumption.
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Polar bear consumption of terrestrial foods – new paper misses the point

A new paper by polar bear biologists (Rode et al. 2015) argues that terrestrial (land-based) foods are not important to polar bears now and will not be in the future – a conclusion I totally agree with – but they miss the point entirely regarding the importance of this issue.

Fat bears on land in the Southern Beaufort, Sue Miller photo, well-prepared for a brief summer fast.

Whatever food polar bears consume in the summer – whether they are on land or on the ice – doesn’t really matter. What matters is how many fat-rich seals they can consume between March and June each year. The fat put on in late winter/spring from gorging on baby seals carries polar bears over the summer, no matter where they spend it.

USGS polar bear biologist Karyn Rode and colleagues (press release here) have tried to frame this issue as one about future survival of polar bears in the face of declining sea ice. However, the fact that polar bears in the Chukchi Sea and Southern Davis Strait are thriving despite dramatic declines in summer sea ice (aka an extended open-water season), proves my point and disproves their premise. Bears in these regions are doing extremely well – contrary to all predictions – because they have had abundant baby seals to eat during the spring (see here and here).

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Polar bears out on the sea ice eat few seals in summer and early fall

We hear endlessly about the polar bears ‘forced’ to go without food for months because of receding summer sea ice — what about all the bears that stay out on the ice over the summer? Presumably, those bears keep hunting for seals – but how many do they actually catch?

Polar Bear Breaks Ice

[Update 9 February 2015: Just to be clear, this post is based on the facts available in the peer reviewed literature — if you think I have missed something, let me know via the “Contact us” page above]
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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.
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Andrew Derocher raises the “starving polar bears” issue in DailyMail interview

In what looks like a follow-up to last week’s CBC documentary, The Politics of Polar Bears, the London (UK) based DailyMail published interviews with polar bear biologists Mitch Taylor and Andrew Derocher (September 9, 2014).

The CBC film did have a one scientist vs. another” flavor about it and this article definitely echoes that approach. My comments below on Derocher’s insinuations and questions about starving bears and global warming.
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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.

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