Tag Archives: Beaufort Sea

Tracking polar bears in the Beaufort Sea May and June updates

At the end of June, there were nine bears remaining from the original 14 that were tagged with glue-on ear transmittors in April 2018 near Kaktovik, Alaska by US Geological Survey biologists.

putting_collar_on_polar_bear_slider_USGS

Below is the June 2018 tracking map (high resolution image is here):

Beaufort tracking USGS bear-movements-June 2018 sm

Original caption: “Movements of 9 satellite-tagged polar bears for the month of June, 2018. These bears received satellite eartag transmitters in 2018 on the spring-time sea ice of the southern Beaufort Sea. Polar bear satellite telemetry data are shown with AMSR2 remotely-sensed ice coverage for 30 June, 2018.”

See the close-up for June 2018 below:

Beaufort tracking USGS bear-movements-June 2018 closeup

As ear tags are notoriously short-lived, there may not be any remaining by the end of July but if there are, I will post the tracks. The map for May 2018 is below.
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Tracking polar bears in the Beaufort Sea resumes after a one year hiatus

Fourteen bears tagged by the US Geological Survey (USGS) on or near the central Southern Beaufort Sea coast in April 2018 (near Kaktovik) will be tracked online over the coming months.

The break in published USGS tagging data from March 2017 to April 2018 was the first since the project began in December 2009 but no explanation for the hiatus has been provided. It is therefore unclear whether no tagging occurred in spring 2017 or data was simply not published online. The last bears followed were tagged in March 2016.

Tranquilized_pb570_S Beaufort March 2014_USGS

In contrast to previous years, this spring all fourteen of the bears have glue-on ear transmitters, which means they are either adult males or juvenile bears rather than females (which are fitted with satellite collars):

“In collaboration with the U.S. Fish and Wildlife Service we are also experimenting with glue-on and ear tag satellite transmitters, which can be deployed on adult male bears and younger, still-growing bears.”

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Archive of 2007 USGS reports supporting 2008 ESA listing for the polar bear

The administrative reports used in 2007 to support the decision to list polar bears as ‘threatened’ under the US Endangered Species Act (ESA) in 2008 disappeared from the US Geological Survey website several years ago. I have archived them here in pdf format to make them easy to find for anyone wishing to access the accuracy of the models, data, and assumptions made in 2007.

Amstrup w triplet_Prudhoe Bay 2005_USGS_sm

Steven Amstrup in 2005, then lead USGS polar bear biologist, with triplet cubs, Prudhoe Bay, AK.

This is a housekeeping post meant for future reference. I’ve included citations for the relevant sea ice projection papers used in the models presented in the 2007 documents and a few other related reports from the same time period. Continue reading

Polar bear specialists double-down on message of future starving bears

The really significant content of a new paper being heavily-hyped by the media1 is what wasn’t said rather than what the authors discovered about metabolic rates and weight maintenance of a small sample of nine Southern Beaufort Sea bears in 2014 to 2016 (Pagano et al. 2018; Whiteman 2018).

Pagano et al. 2018 photo released to press 2

This paper does not document starving or dying bears but merely found some (5/9) that lost weight when they should have been gaining, given that early April is the start of the ringed seal pupping season (Smith 1987) and the intensive spring feeding period for polar bears (Stirling et al. 1981).

The question is, why were Southern Beaufort Sea polar bears off Prudhoe Bay (see map of the study area below), still hunting and capturing only adult and subadult ringed seals from sea ice leads when newborn ringed seal pups and their mothers should have been plentiful and relatively easily available in their birth lairs on the sea ice (see below)?

Ringed seal lair_snow and ice thickness_PolarBearScience_sm

“Using video collar data, we documented bears’ hunting behavior and foraging success. Bears used sit-and-wait tactics to hunt seals 90% of the time, and stalking comprised the remaining 10% of hunts (movies S1 to S4) (19). Bears that successfully killed and ate adult or subadult ringed seals either gained or maintained body mass, whereas bears that only scavenged or showed no evidence of eating lost mass.”

There was no discussion in the paper of ringed seal birth lairs, or sea ice conditions at the time of the study, but several mentions about what might happen in the future to sea ice and potential consequences for polar bears. The press release did the same.

However, as you’ll see by the sea ice thickness maps below, there may be good reason for the lack of ringed seal lairs, and a general lack of seals except at the nearshore lead that forms because of tidal action: the ice just a bit further offshore ice looks too thick for a good crop of ringed seals in all three years of the study. This is reminiscent of conditions that occurred with devastating results in the mid-1970s and mid-2000s (Burns et al. 1975; Cherry et al. 2009; Harwood et al. 2012, 2015; Pilfold et al. 2012; Stirling 2002, Stirling et al. 1987). Those events affected primarily bears in the eastern half of the Southern Beaufort and were almost certainly responsible for the recorded decline in SB bear numbers in the 2001-2010 survey (Bromaghin et al. 2015; Crockford 2017; Crockford and Geist 2018).

It seems very odd to me that Pagano and colleagues suggested no reasons for the unexpectedly poor showing of polar bear hunting success during their study except a bit of hand-waving about higher-than-we-thought metabolic rates in the bears. For years, I’ve worried that the inevitable next episodes of thick Southern Beaufort spring ice would cause problems for polar bears and seals but we wouldn’t know it because whatever effects were documented would be blamed on reduced summer ice: I suspect that time may have come.

Pagano et al. 2018 polar bear fat and energy fig 1

Figure 1 from Pagano et al. 2018 cropped to show only the study area off Alaska.

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Much more sea ice in NW Hudson Bay this year than 2016 or 2015 at 27 May

In recent years, sea ice loss over Hudson Bay has begun with open water in the NW corner (which is just as likely due to prevailing offshore winds as ice melt) rather than along the east coast but this year that patch of ice is smaller than its been for the last two years. In addition, despite two patches of open water at either end of the Beaufort Sea, most of the coast of Alaska is still covered in thick ice — much more than existed last year, yet masses of polar bears did not die as far as I know (actually, WHB bears came ashore in excellent condition last year).

Sea ice Canada 2017 May 27

Compare to previous years:

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Fall Arctic ice growth often differs regionally: 2016 compared to other years

Arctic sea ice is spreading out quickly from its central basin summer refuge – according to this NSIDC Masie ice chart, it has already grown more than 2 mkm2 beyond the annual minimum reached in early September. Ice is already pushing south into the eastern Beaufort and the archipelago of Franz Josef Land in the Barents Sea.

masie-sea-ice-2016-oct-20-cropped-and-marked_polarbearscience

Over the next couple of weeks, shorefast ice will start forming along the coasts of North America and Eurasia (see the first bits off Alaska in the 21 October CIS map below), which will eventually meet the expanding Arctic Basin pack to fill the Basin and Canadian Arctic Archipelago with ice – as it has done for eons.

sea-ice-extent-canada-2016-oct-21_cis

The evidence from the last decade or so suggests that by the end of October, most of the Arctic north of the 79th parallel (see map below) will be filled with ice – although the Chukchi Sea (north of the Bering Strait) may not fill until sometime in November:

79-th-parallel-north_wikipedia

Polar bears usually resume hunting as soon as sea ice conditions permit in the fall, since it’s their last chance to top up their fat reserves before the dark and cold of winter when hunting may become next to impossible.

I’ve copied ice charts from the Masie archives for some previous years at 31 October below.

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Tracking Western Alaskan polar bears in the Beaufort in Sept – all 3 chose Canada

All three polar bear females tagged in the Southern Beaufort Sea far west of Kaktovik (near Barrow) spent all or most of September onshore in the Northern Beaufort area of Canada.

beaufort-tracking-usgs-bear-movements-september-2016-lg-closeup

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