Who is the "king" of tigers? - Bengal or Amur

[peter]

(04-04-2020, 10:10 AM)GuateGojira Wrote:

(04-02-2020, 10:06 AM)strana Wrote: Guate,
First, thanks for another very interesting material.
However, I think that the size of modern Amur tigers are underestimated. There are some pics of very impressive wild tigers in Russia here in Wildfact; I would not be surprised if some of them reach 250 kg+. I believe only the young/not very healthy are weighted. Wild Bengals and Amur might have similar size, but ok, it is just speculation.

Hello, thank you for your words.

About the size of the Amur tiger, in fact the data on the image takes in count both historic and modern weights. Surely there are photos of very impressive male in the Russian Far East, but sadly none of them has been weighed, so for the moment the biggest male recorded between 1992 to 2012 (the last year when weights were published) was of 212 kg.

Now  about the sample, it is not true that only young or not-healty males were weighed, let me explain to you first. In 2005 Dr Slaght and other scientists published a chapter in the monograph of the Amur tiger published by the Siberian Tiger Project (in Russian only), especifically the chapter No. 6. Now, in that document they calculated an average weight of 176.4 kg (n=18; range: 125 - 205 kg) for males and 117.9 kg (n=13; range: 113 - 129 kg) for females. However those figures includes specimens that were not in good shape, in fact the weight of 125 kg was for male in such a bad shape that was eutanized! Also, the sample includes specimens over 3 years old, as for scientists an animal is "adult" when they are sexually mature. Now, in order to get a more reliable average figure I investigated all the reports about the Siberian Tiger Project, plus the new males/females captured by the Amur Tiger Programme and I excluded the specimens in bad shape, although it was not posible to exclude the specimens between 3-4 years old for obvious reasons. At the end, my result was of an average weight of 190 kg (n=23; range: 155 - 212 kg) for males and 121 kg (n=15; range: 110 - 136 kg) for females, taking in count only the specimens captured between 1992 and 2012. For the moment those are the most reliable figures about the body mass of the Amur tigers, but take in count that after the year 2000 more males of 200 kg or over had been captured, so I think that there is a big posibility that males over 215 kg are now there in the Russian Far East.

If we use the weights of the Amur tigers in the past, we can see that they were of about the same size of the Bengal tigers, with confirmed weights of about 250 kg and the skulls shows that they could be slightly longer too.

THE RELATION BETWEEN HEEL WIDTH AND WEIGHT IN WILD AMUR TIGERS

Decent explanation on the problems distinguishing young adults (3-4 years of age) from adults (5 year and over), Guate. Most reports on young adult males I have suggest they range between 150-180 kg. The skulls I measured show significant differences between age groups. If a table has young adults, chances are the average will be affected, especially in wild tigers. 

As to the weight of wild Amur tigers captured or photographed after 2005. In brown bears, heel width is a good indicator of weight. My guess is it isn't much different in big cats. In most male Amur tigers, the heel width ranges between 10,0-12,5 cm. If you use everything you have to get to a table that has information on age, heel width and weight, chances are you'll get a result. 

We know male tigers (including immature individuals) with a heel width of 10,0-12,5 cm. range between 100-200 kg. We also know the heel width of some individuals exceeded 12,5 cm. As far as I know, there're three reports about male Amur tigers with a heel width ranging between 13,0-14,0 cm. One of them is mentioned in 'Winter ecology of the Amur tiger' (A.G. Yudakov and I.G. Nikolaev, 2nd revised edition, Vladivostok, 2012, pp. 144). The two other reports are recent. The male below has a heel width of 13,5 cm. The photograph was first posted by Lycaon: 

*This image is copyright of its original author

It isn't easy to get to a guesstimate on his weight, because there's no table with information on the relation between heel width and weight in wild Amur tigers. In brown bears, the relation between heel width and weight is quite strong. In large individuals, a relatively modest increase in width often results in a significant increase in weight. I'll try to find the table. 

Chest girth and zygomatic width also are quite good indicators of weight. The problem, of course, is we know next to nothing about wild Amur tigers featuring in videos and photographs. This is the reason we need to find out a bit more about the relation between heel width and weight in Amur tigers. My guess is we can get a result. The information is there. 

Here's a table with information on the relation between heel width ('pad size'), weight and the effect of growth in wild Amur tigers:

*This image is copyright of its original author

Here's a bit more on the relation between chest girth and weight and zygomatic width and weight in brown bears: 

https://www.bearbiology.org/wp-content/uploads/2017/10/Glenn_Vol_4.pdf Reply