Here is the follow-up I promised to my post on the July track map for 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.
The track map for August was posted on the USGS website on September 4th and is copied here below (Figure 1). The ice moved a bit further offshore during August but not nearly as far as it did in 2012. The ten bears from July were down to eight – their collars might have stopped working or fallen off (most likely), they might have left the area entirely (also possible) or they might have died (the researchers don’t say which).
Figure 1. “Movements of 8 satellite-tagged polar bears for the month of August, 2013. Polar bears were tagged in 2013 on the spring-time sea ice of the southern Beaufort Sea. All 8 of these bears have satellite collar transmitters [i.e., all are females]. Polar bear satellite telemetry data are shown with Ice Analysis charts from 26 August, 2013. Ice Analysis charts are made available by the National Ice Center. The land cover is made available by Natural Earth. Click on the above image to enlarge.” [Note that the dots with the polar bear icons are the end points (end August), while the other end of the string is their position in early August. The yellow dot is behind the purple dot, on shore; two of the bears present in July (see Fig. 2 below) are no longer being tracked – their collars might have stopped working or fallen off (most likely), they might have left the area entirely (also possible) or they might have died. The researchers don’t say.]
So, of the eight polar bears still being followed by USGS researchers in August, three were on shore and five were on the ice. Only time will tell if the three females on shore are pregnant and preparing maternity dens for the winter, but this seems the likely reason they are not on the ice with the others.
I’ll post the track map for September when it is available in early October at the USGS website.
The map for July 2013 is below, for comparison: Continue reading
Posted in Life History, Sea ice habitat
Tagged Alaska Science Center, Beaufort Sea, Chukchi Sea, females with radio collars, Regehr, Rode, satellite radio collars, summer ice minimum, summer sea ice, swimming polar bears, tracking polar bears by satellite, US Fish, us geological survey, USGS
Tracking Beaufort Sea polar bears over the summer — what can it tell us about how important the position of summer sea ice relative to the shoreline in this region is to these bears? Do Beaufort Sea bears get stranded on shore like the polar bears in Davis Strait and Hudson Bay?
Polar bear biologist Eric Regehr (with the US Fish & Wildlife Service, or FWS) has a team working with US Geological Survey researchers (USGS) in the southern Beaufort tracking where adult female polar bears go throughout the year. This is part of on-going research in the Beaufort and Chukchi Sea (see previous post here; see also Fish & Wildlife 2009; Polar Bear News 2010 and 2013; Rode and Regehr 2010, pdfs below; and just out, the “accepted” version of the Rode et al. paper discussed here, and announced in my last post here).
The researchers have been posting a summary map at the end of each month on the USGS website showing the tracks of the females they fitted with radio collars the previous spring — for 2013, and back to 2010. They can’t put collars on male bears because their necks are larger around than their heads, so a collar would just slip off.
I’ve posted the July 2013 track map below, which shows all ten bears out on the ice, and the previous month (June 2013) to compare it to (the August map should be out shortly). I’ve included a few maps from 2012 to allow you to compare this year’s results to the situation last summer.
The August tracks should be available after the Labour Day weekend – check back next week to see where the bears have been this month. I’ll post the map here or you can go to the USGS website directly. [UPDATE Sept 4, 2013: The August map is up, posted here.]
Posted in Life History, Sea ice habitat
Tagged Alaska Science Center, Beaufort Sea, Chukchi Sea, Davis Strait, females with radio collars, Hudson Bay, Regehr, Rode, satellite radio collars, summer ice minimum, summer sea ice, swimming polar bears, tracking polar bears by satellite, US Fish & Wildlife, USGS