Dr. Susan Crockford
My open-access, peer-reviewed paper on the ecology of ancient polar bears in relation to sea ice has just been published in Open Quaternary. It’s called ‘Polar Bear Fossil and Archaeological Records from the Pleistocene and Holocene in Relation to Sea Ice Extent and Open Water Polynyas’.
A unique compilation of more than 104 polar bear skeletal records from the Holocene and late Pleistocene shows that most ancient remains are associated with existing or ancient open water polynyas or the expansion of sea ice during past cold periods. This big-picture analysis indicates that as they do today, polar bears were most commonly found near polynyas throughout their known historical past because of their need for ice-edge habitats.
Read my longer summary below and download the paper here. This is a much-updated and expanded analysis based on an informal study I did in 2012.
Polar Bear Fossil and Archaeological Records from the Pleistocene and Holocene in Relation to Sea Ice Extent and Open Water Polynyas
No Arctic animal is more iconic than its apex predator, the polar bear (Ursus maritimus). However, its distribution across time and space has not previously been reported. Natural death skeletal specimens of this species (‘fossils’) are rare but archaeological remains are much more common. This historical compilation presents the record of known ancient polar bear remains from fossil and archaeological contexts before AD 1910.
Most polar bear remains date to the Holocene (the last 11,700 years) and come from human habitation sites within the modern range of the species. Specimens found outside the modern range (extralimital) have been documented in the north Atlantic during the late Pleistocene (ca. 115,000- 11,700) and the southern Bering Sea during the middle Holocene (ca. 8,300-4,200 years ago), in conjunction with natural expansions of sea ice during known cold periods.
Surprisingly, the single largest assemblage of this species is also the oldest archaeological site with polar bear remains. Zhokhov is one of the northern-most islands in the East Siberia Sea, Russia which polar bears females still use today as a denning area. The site was occupied primarily during a short period (ca. 8,000-7,900 years ago) near the beginning of the Holocene Climatic Optimum (about 9,000-5,500 years ago), when the Arctic was warmer than today. Almost 6,000 polar bear bones were recovered from Zhokhov Island, which represented about 28% of all the animal remains identified at the site.
In virtually all other archaeological sites worldwide, less than 3.5% of identified remains were polar bear. The Zhokhov Island assemblage is also our first evidence of the return of polar bears to the western Arctic after extraordinarily thick sea ice during the Last Ice Age (ca. 30,000-19,700 years ago) drove seals and bears into the north Pacific.
This study shows that polar bear remains are most often found in proximity to areas where polynyas (recurring areas of thin ice or open water surrounded by sea ice) are known today and which likely also occurred in the past. As a consequence, the oldest known fossil (dated to about 130-115k years ago) and the oldest known archaeological specimens (dated to about 8,000 years ago) were likely associated with polynyas as well. This pattern indicates that as they do today, polar bears may have been most commonly found near polynyas throughout their known historical past because of their need for ice-edge habitats at which to hunt seals, their primary prey.
Citation: Crockford, S. J. 2022. Polar bear fossil and archaeological records from the Pleistocene and Holocene in relation to sea ice extent and open water polynyas. Open Quaternary 8(7): 1-26. https://doi.org.10.5334/oq.107