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04-17-2014, 04:11 AM( This post was last modified: 07-05-2018, 04:29 AM by peter )
02 - EVOLUTION (continuation)
TIGER DISTRIBUTION IN THE LAST GLACIAL MAXIMUM (models 1 and 2)
*This image is copyright of its original author
*This image is copyright of its original author
Both maps (based on a number of fundamental assumptions) predict tigers in Japan and Palawan (as well as Borneo). They also explain which subgroups would have been isolated, but they do not offer an explanation as to why tigers would have survived on some islands and not others.
Late's take Japan. A quite predatory and aggressive brown bear subspecies (Ursus arctos lasiotus) survives to this day, but tigers apparently disappeared a long time ago. Humans seem unlikely, as they would also have targeted the more dangerous brown bears. There has to be another reason.
Anyhow. Let's move to Caspian tigers. It is generally assumed tigers followed the silk route when they spread, which means they walked north of the Gobi and the Himalayas. Not likely according to those who produced both maps:
*This image is copyright of its original author
Both maps and the conclusions drawn were partly confirmed by recent research, but there also are contradictions. I noticed the remark on tigers west and east of the Caspian in particular. Morphological information and rumours about the size and character of Caspian tigers in different sources all point towards different local types east, west, north-east and south of the Caspian. Could be true, as both maps above also indicate some subgroups might have been isolated for a considerable period of time.
There is very little information on tigers in most regions. Brandt (1856), quoting from Roman sources, wrote Caspian tigers were a bit smaller and wilder than tigers east of the Indus River, but the information we have from Iran (south-western part of the Elburz Mountain Range in the north-west and Mazanderan in the east) says some male Caspian tigers were hardly, if at all, smaller than Indian tigers (total length). They have shorter skulls, but the sample is small and it could be Caspian tigers, living at relatively high altitude, adapted in developing a shorter and more inflated maxillary bone. Still unclear to me, but I noticed a remarkable difference between both sexes.
a) Syr-Darja, adult female (1950):
*This image is copyright of its original author
b) Berlin Zoo (roundabout 1900). Both well marked and smaller than an average Indian tiger: