Collaring the confusing ancestry of a (usually) nondescript bear

Everyone knows that the brown bear can be one of the plainest-coloured of large mammals.

However, who knows that there is a geographically variable pale collar in some individuals, usually restricted to juveniles? And who understands the implication of this: that what we call a species is not, strictly speaking, a species?

https://media.greenpeace.org/archive/Grizzly-Bear-Cub-in-Canada-27MZIFJW1EM1W.html
https://www.smh.com.au/world/north-america/friendly-bear-cubs-with-no-fear-of-humans-found-to-have-brain-virus-20210406-p57gty.html
https://www.istockphoto.com/photo/mummy-bear-and-her-three-little-puppies-gm1148397622-310125519
https://www.istockphoto.com/photo/brown-bear-cub-playing-on-the-field-among-white-flowers-gm1134868710-301707047
https://www.istockphoto.com/photo/brown-bear-cubs-playfully-fighting-gm1134874099-301707089
https://www.istockphoto.com/photo/wild-brown-bear-cub-closeup-gm961208148-262475968
https://www.istockphoto.com/photo/sow-grizzly-and-coy-gm1152908011-312958525
https://www.istockphoto.com/photo/european-brown-bear-standing-gm1341296504-421090357

In order to understand this aberrant collar, a good start is to acknowledge that Homo sapiens is not a pure species, but in part an interspecific hybrid (https://medlineplus.gov/genetics/understanding/dtcgenetictesting/neanderthaldna/#:~:text=As%20a%20result%2C%20many%20people,more%20about%20these%20early%20humans).

Could it be that the brown bear, too, is an interspecific hybrid (https://www.nature.com/articles/srep46487 and https://www.nature.com/articles/s41598-019-40168-7), with the occasional trace of a collar indicating the mixed ancestry?

This may sound strange to anyone with a conventional concept of 'descent with modification'. However, calling our species Homo sapiens, or calling the brown bear Ursus arctos, is as much convention as fact.

The word 'hybrid' is itself hard to define objectively. This is because many - perhaps most - species have been produced by 'lateral evolution' as well as 'vertical evolution'.

In the case of humans, we hardly know what our Neanderthal or Denisovan inheritance looks like. I.e. we are unsure which phenotypic features of e.g. modern Europeans reflect a partly Neanderthal ancestry, and which phenotypic features of e.g. Melanesians indicate a partly Denisovan ancestry.

However, in the case of the brown bear the origin of the pale collar is easier to guess: the Asian black bear (Ursus thibetanus, https://en.wikipedia.org/wiki/Asian_black_bear and http://justfunfacts.com/interesting-facts-about-asiatic-black-bears/).

The Asian black bear has a whitish collar, albeit an inconsistent one (http://justfunfacts.com/wp-content/uploads/2017/10/asiatic-black-bear-4.jpg). And because it has had contact with the brown bear all the way from Iran to Manchuria (https://en.wikipedia.org/wiki/Asian_black_bear#/media/File:Asian_Black_Bear_area.png), there has been opportunity for introgressive hybridisation over a long period - and over an area eventually spreading so far afield that any memory of an ancestor has been lost.

The form of the brown bear in which the pale collar is clearest and most consistent, and in which it persists in adults, is that of western China.

Ursus arctos pruinosus
https://alchetron.com/Tibetan-blue-bear
https://www.dreamstime.com/stock-photo-tibetan-blue-bear-horse-bear-one-rarest-brown-bears-world-image92634205
https://www.dreamstime.com/stock-photo-tibetan-blue-bear-horse-bear-sitting-ground-one-rarest-brown-bears-world-image92634346
https://www.zoochat.com/community/media/tibetan-blue-bear-ursus-arctos-pruinosus.244453/
https://blog.nature.org/science/files/2013/03/Tibetan-blue-bear1.jpg
https://blog.nature.org/science/files/2013/03/Tibetan-blue-bear-III.jpg
https://www.zoochat.com/community/media/tibetan-blue-bears-begging-for-food.243300/
https://www.flickr.com/photos/62108170@N05/5740454820
https://naturerules1.fandom.com/wiki/Tibetan_Blue_Bear?file=34485.jpg
https://zooinstitutes.com/animals/tibetan-blue-bear-beifang-forest-zoo-103157.html

However, the pale collar tends to be noticeable also in

eastern Siberia (http://www.bearconservation.org.uk/east-siberian-brown-bear/ and http://www.galerie.pierrewildlife.com/main.php?g2_itemId=113098), and
Korea and nearby regions (see first comment in the comment stream below).

Furthermore, some individuals retain traces of the pale collar in adulthood even in Scandinavia, more than 4,000 km from the range of the Asian black bear (http://www.bearconservation.org.uk/eurasian-brown-bear/ and https://www.shutterstock.com/nb/image-photo/european-brown-bear-forest-landscape-summer-1440364292).

In North America - a continent removed - the pale collar is restricted to some juveniles, and perhaps only in the northwestern parts of the continent. But the fact that it occurs at all is noteworthy.

And the lack of hypotheses so far, for such a striking and photogenic pattern, reminds us that the biology of animal colouration is still in its infancy.

Posted on Σεπτέμβριος 27, 2021 0839 ΜΜ by

milewski

Σχόλια

The subspecies illustrated below is Ursus arctos lasiotus, which ranges from northern Japan through Sakhalin to the Russian far east and Korea. The whitish band on the chest and ‘throat’ is associated particularly with an insular population in Shiretoko National Park.

Part of the explanation for this distinctive marking is that this subspecies of U. arctos is one of the darkest, some individuals being virtually black. I.e. the development of this pale insignia is associated, as in Sarcophilus harrisii (https://www.inaturalist.org/taxa/40232-Sarcophilus-harrisii), with a general darkening of the rest of the pelage.

I emphasise that even in Shiretoko National Park, most individuals probably do not possess these markings. So, as in Sarcophilus, one of the striking aspects of these insignia is how individually variable they are in presence/absence as well as in shape and placement.

There is a broader tendency for juveniles to possess a pale collar on the dorsal surface of the neck, which disappears as the animal reaches maturity. This marking is related to the one shown below, because what we are looking at is a single nebulous and erratic band that can extend variously from the dorsal surface of the neck right around the chest and ‘throat’. Juveniles possess this collar in various subspecies of U. arctos, including those in North America.

However, the ontogenetic fading of the pale marking is another question, not relevant to Sarcophilus. This is because the pale insignia in Sarcophilus are ‘set’ in infancy and remain the same throughout life in any given individual.

All the following photos show Ursus arctos lasiotus, mainly in Shiretoko National Park.

http://i.dailymail.co.uk/i/pix/2016/05/29/12/29C684A800000578-0-image-a-35_1464522382175.jpg

https://www.ana-cooljapan.com/destinations/hokkaido/shiretokonationalpark

https://ichef.bbci.co.uk/images/ic/480x270/p02nm9jb.jpg

scroll in https://www.shiretokoserai.com/en/tour/4SS001/

scroll in https://www.saiyu.co.jp/en/itinerary/IJHK18/

https://mainichi.jp/english/articles/20180811/p2a/00m/0na/019000c

https://www.global.hokudai.ac.jp/blog/55/

https://t-ec.bstatic.com/images/hotel/max1024x768/109/10997016.jpg

http://3.bp.blogspot.com/_EqtFCwNOVc4/SSJrxscgHTI/AAAAAAAAD8A/WY4FkPw4eTM/s320/SDC18705.JPG

http://blog-imgs-41-origin.fc2.com/p/a/r/paraparadisezooeng/20081006173423.gif

http://farm4.static.flickr.com/3310/3631768327_a7be2d4208.jpg

http://ichef.bbci.co.uk/wwfeatures/wm/live/1280_720/images/live/p0/2t/vw/p02tvwhc.jpg

http://ichef.bbci.co.uk/wwfeatures/wm/live/1280_720/images/live/p0/2t/vw/p02tvwxz.jpg