Daily Archives: January 28, 2015

Polar bear penises not breaking due to PCBs – new paper full of “coulds” and “maybes”

This is a short discussion about research on polar bear penis bones, regarding a new paper that sent several of the Internet’s most juvenile science headline writers off the deep end.1

Marine mammal penis bones_not labeled_PolarBearScience_2015_sm

Short quiz first. Above are the penis bones (each called a baculum, plural bacula) of three marine mammals – one is from a bearded seal, one from a polar bear and another from a Steller sea lion. Which one do you think is the polar bear? Answer below.
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Claim of range-contraction of polar bears due to declines in summer sea ice doesn’t hold up

Have polar bears suffered a contraction of their historical range due to recent declines in summer sea ice? Buried in a recent journal article lies such a claim, one I can’t recall having seen before. That makes it worth close examination.

Figure 2. A drawing of polar bears on St. Matthew Island that accompanied the May 1, 1875 Harper’s Weekly Journal of Civilization article written by Henry Elliot. See here.

A drawing of polar bears on St. Matthew Island that accompanied the May 1, 1875 Harper’s Weekly Journal of Civilization article written by Henry Elliot. See here.

The assertion appears in the introduction of a recently published paper that got a lot of attention online (“Implications of the Circumpolar Genetic Structure of Polar Bears for Their Conservation in a Rapidly Warming Arctic” by Peacock and colleagues (2015), discussed previously here, news coverage here and here).

Here is how the authors put it:

There is already evidence of change in the contemporary distribution of polar bears. For example, polar bears, once common in Newfoundland [29], are now seen there only infrequently and in small numbers. Similarly, polar bears once regularly summered on St. Lawrence and St. Matthew islands in the Bering Sea [30–32]. Now they are irregularly observed in the Bering Sea and do not spend summers on St. Matthew Island. Although these changes in polar bear distribution may also have been related to overharvest, the recent reductions in the extent of sea-ice due would prevent current and regular use of these areas.[my emphasis]

There are three main reasons the claim doesn’t hold up to scrutiny:
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