Tracking polar bears in the Beaufort Sea: October map

Here is the October follow-up to my post on the July 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 track map for October is copied below (Figure 1).

By the end of October, ice reached the coast in several areas. The ten bears from July were down to seven – 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. Original caption: “Movements of 7 satellite-tagged polar bears for the month of October, 2013. Polar bears were tagged in 2013 on the spring-time sea ice of the southern Beaufort Sea. All 7 of these bears have satellite collar transmitters. Polar bear satellite telemetry data are shown with AMSR2 remotely-sensed ice coverage for 31 October, 2013. AMSR2 data are made available by the University of Bremen (http://www.iup.uni-bremen.de:8084/amsr2/). The land cover is made available by Natural Earth (http://www.naturalearthdata.com/).” Click to enlarge. Original here.
Note that the dots with the polar bear icons are the end points (end October), while the other end of the string is their position in early October.

A few things to note:

The female that was on Banks Island at the end of September (light brown) is now back on the ice but still in the Northern Beaufort subpopulation region.

During October, the dark brown female made her way across the ice from the Southern Beaufort to the Chukchi Sea subpopulation region.

Three females were so close together on the shore (near Prudhoe, Alaska) during September that their dots overlapped (and lack of tracking “strings” means they didn’t move much). During October, two of these three bears made their way east toward Kaktovik.

The female represented by the light green dot and tracking string spent September and most of October at the southern edge of the pack ice but by the end of October, she seemed to be heading towards land.

Finally, and most significantly, despite the fact that all of these bears were tagged in the spring (mating season for polar bears) in the Southern Beaufort, two of the seven now being tracked have left the region: one to the Northern Beaufort and one to the Chukchi Sea subpopulation region. These regional boundaries are known to be crossed — here you see it in action.

The map for September 2013 is below, for comparison:

Figure 2. “Movements of 8 satellite-tagged polar bears for the month of September, 2013.” [Note that the dots with the polar bear icons are the end points (end September), while the other end of the string is their position in early September, indicating that the ice is now moving towards the shore. The pink dot present in August is almost entirely obscured by the purple dot, on shore in Alaska and the light brown dot is ashore on Banks Island, centre right of the map. Click to enlarge