ON THE EDGE OF EXTINCTION - A - THE TIGER (Panthera tigris)

[GuateGojira]

Short note: On the tiger subspecies.

I know that I am still don't present my post about Sankhala (difilcuties of time, but I already have the material), but this topic on the tiger subspecies is something very important from my point of view. 

Recently I had a conversation with a poster about this point and I participated my idea about this. However, after that I started to think again about that, even before to read his/her answer about my position, and I think that we need to re/think the "two subspecies" scenarions, even not taking in count the new study of 2018! Let me explain why, and I will use the same answer that I send to my friend, but with some modifications:

Regarding the tiger subspecies, I think that we must be very carefull with those results (talking about the results of the Cat Specialiest Group). Although it make sence that tigers only have two subspecies and I follow that conclution, I also believe that we must not mix tiger populations yet. The problem is that tigers at 2019 are so separate geographically that make no sense to mix them in the wild, nor even to reintorduce them in areas where they are no more. For example, the idea of introduccing Amur tigers in the Caspian region make no sence as we need to conserve the tigers that we have before to think to put more tigers in danger. Tigers are very well separated in these days, with tigers in India already divided in 4 or 5 areas (Western Ghats, Central India, Terai (and Assam?) and Sundarbans), those from Indochina only living and reproducing in Thailand in these days (no signal of reproduction anymore in Myanmar and possibly extinct in Laos and Cambodia), those of Malaysia already separated in the peninsula and the most importat of all, the Amur tigers are separated from the other populations for more than some hundreds of years; interestingly the Sundarbans tigers and the Amur tigers are suggested to be clasified as different Evolutionary Conservations Units (ECU) at the brink of been a different subspecies, even more than the Malayan tigers! So there is no need to relocate tigers in this moment, we need to conserve tigers in those specific areas (India/Nepal/Buthan - India/Bangladesh - Thailand - Malaysia - Russia/China) of the mainland. Sumatran tigers are very different animals from Mainland that deserve they own subspecies status and to be honest, we don't have enough evidence to suggest a real difference between the Sumatran and the Javanese or Balinese tigers.

Regarding the zoos, you are right, there is no need to mix the tiger, Amur tigers should be kept like they own population as they are different, the same with Sundarbans. Tigers from the India Subcontinent are so far away from those of Thailand, there there is no good idea to mix them, but in the past probably there were "hybrids" in the region of Myanmar (according with Dr Hunter, there is no evidence of reproduction of tigers in Myanmar anymore). Now, Thailand tigers live in they own "island" and "Indochinese" tigers only live in Thailand zoos; tigers from Malaysia are keept in USA and Europe and as far I know they will kept them like they are, no mix in they plans. The BIG problem is with the population of mix tigers in USA, specially those cocktails of Bengal/Amur/White tigers. Those huge "American" tigers are a real waste, sadly, as they are two groups separeated from thousands of years of evolutions (India and Russia were the last tigers to evolve and both came from diferent origin populations) and that represent the last tigers that evolved, the biggest of all, but in completelly diferent habitats. Interestingly this mix Bengal/Amur tigers are doing well in South Africa with John Varty! So I think that the zoos should manage the tigers like they are in this moment, no mix at all. This is the list that I think is the correct one for the "subspecies" and the ecological variations separated enoght to be clasified as ECU:
1 - Mainland - Tigris:
   * India/Nepal/Bhutan - "Bengal"
   * India/Bangladesh - "Sundarbans"
   * Thailand - "Indochina"
   * Malaysia - "Malayan"
   * South China - "South China" (in South Africa, but not those of Varty)
   * Russia and north China - "Amur"
2 - Sunda - Sondaica:
   * Sumatra/Java/Bali

Interestingly the tigers of India, Nepal and Bhutan looks somewhat differente (even between Indian parks), but as they are traditionally clasified as "Bengal" they continue been keep together. The last genetic studies speak of a big genetic variation in the population of the Indian subcontinent, but not enoght to classified them as subspecies as they own.

Now, this is the new part that was not in my original answer: The scenario when the Mainland tigers are a single subspecies is based in the fact that the tiger populations were united with no boundaries in the entire continent, there was no river or no mountain (except for the Himalayan and the Kutch) that could separate the tigers, and taking in count that tigers can travel huge distances, tigers from India could travel to Indochina or Russian tigers could travel to South China, with no problem. Only the Sunda tigers were separated from the main population. However, this scenario no longer exist and the current populations are so isolated from each other that there is reason to try to join them in a single population again.

We know that the tiger subspecies are based in pourly descriptions and very small samples (only the Indochinese tiger is described by more than 20 specimens, all the other do not have more than 5!), and it was used size and pelage like the base of the differences. I am pretty sure that nodoby could distinguis a Indochinese tiger from a Bengal tiger based in pictures, there are also dificulties to distinguis tigers from different parts from India, appart from Sundarbans, even worst, there are Bengal tigers that look exactly the same than Amur tigers, particularly those from Buthan! So I am agree that in the time before the human intervention, the differences of size and pelage among tigers were clinal and by no means evidence of susbspecies. I still remember that Mazák (1983 & 2013 reprint) presented a draw of a skull from a Bengal tiger from the Assam that looks like a transitional form between the Indian and the Indochinese skulls that he presented in his document of 1981. However, this is not the case anymore as very big changes happened to the tiger populations.

At 2019, like I described before, tiger populations are very well separated, so it is more than obvious that the "subspecies" that existed today were created by the humans, the genetic differences were probably the result of "selection" by the specimens that managed to survive until our days. Let's take each population:

1. Amur - Caspian: There are some differences in the coat pattern, but there is a big overlap and genetic studies shows that there is practically no difference between them. Analysis of the skulls show the same, as the Caspian and the Amur tigers are the only ones with huge satigal crests, broad snouths and adaptations to hunt the big wild boar. There is no doubt genetically and morphologically speaking that they were a single population. The Amur tiger was bigger just because the prey base was larger in the Russian Far East and the habitat better for tigers, at difference of the dry regions of the Caspian and central Asia. Modern Amur tigers are the result of a huge hunt and altough they were smaller when the studies of scientists started in the region, new records shows everytime more specimens over 200 kg, up to 212 kg at the moment (as far I know).

2. India/Nepal/Buthan/Bangladesh: This was a huge population, among the biggest and interconnected until humans separate them because of the hunting and the agricultural development. The last genetic analysis made by Dr Mondol found that tigers in India had the biggest genetic diversity and the population of the Sundarbans (India/Bangladesh) are different enough to be clasified as a completellly diferent conservation unit, in fact there is more difference between the mainland tiger and the Sundarbans tiger than between the Caspian and the Amur tigers! I don't know if the last document of Dr Luo and the team researched specimens from Sundarbans, but following they ideas, this population is at the brink of been another man-made subspecies. The size amoung this population is the same (Terai and Assam slighlty larger) but those of Sundarbans are of the same size than the tigers from the Sunda.

3. Indochina - Malaysia: Tigers in this region are a contradiction. Some sources say that were as small as Sunda tigers, other as big as Bengal. The truth is that Mazák investigation (probably using wild and captive specimens) shows that were smaller (150 - 195 kg) than the Indian tigers, but were they? In the book "Tigers in the Snow" there is a part where is says that Dr Alan Rabinowitz investigated from his part the size of the Indochinese tigers and found no difference between those from India, except that the Indochinese tigers were probably lighter. This is corroborated by modern studies in Thailand where they present weights of 164-209 kg, which is about the same than the modern Amur tigers (155 - 212 kg) but still less than Bengal ones (184 - 261 kg). However in body dimentions, taking in count that Nepalese/Indian and Thailand tigers were measured along the curves with a straight line while those from Russia were measured along the curves with the tape loose, the body size is about the same between the populations, with the Bengal specimens surpasing the other populations.


The case is worst with the Malayan tigers. There is no doubt that the tigers in this region were smaller on average, but the largest specimens were as large as those from India and Russia. In fact, based in the skull size, the populations were about the same size: Bengal - 329-378, Amur - 341-383, Indochina/Malaysia - 319-370 (including the new skull clasified as Malayan based in DNA). So again, we can see that the diference is very small and taking in count specimens that are still unknown or lost from the Indochinese region; weight based, the maximum weights from Bengal, Amur and Indochina were about 250-260 kg. Now, what happen in modern days, there are no reliable weights from wild Malayan tigers, just some estimations of up to 130 kg and a weight of 170 kg reported in a news page of the web. In captivity the Malayan tigers are of the same size than those of Sumatra (109 - 132 kg), so it seems that the new Malayan population is already different in size (a reduction more dramatic than those from Russian tigers?) and the coat pattern is different. So other example of a man-made subspecies separated from the other Indochinese tigers (now only in Thailand, for the long term at least).

4. South China tigers: There is not to much to say, only that these tigers were the smaller of all the mainland subspecies, but this is based in very few specimens, again. There is evidence than those from the northern region of China (still not the Manchurian territory) were relatively large specimens, with at least one male of 190 kg. So there is a posibility that there were a cline on the size of tigers trough China. However in modern times there are no more wild tigers in the Amoy region, and those in existence are only in captivity with maximum weights of about 150 kg, altought I think that those breeding in South Africa by the "Save the China's Tiger" project are probably bigger than those in captivity in China. The idea that these tigers are "primitive" came from an study of Dr Herrington but her study has been critizised by Dr Kitchener and the last study of Dr J. H. Mazák do not suport that point of view. However, as the genetic studies shows that they may be unique in DNA terms, they deserve to be preserved witouth the intervention of other populations, altough we must not forget that Dr Luo and her team in 2004 already found Indochinese DNA in that captiver population in China.

As we can see, there are alraedy separations between the populations, and incredibly those separated subspecies match those from the accepted susbpecies by Dr Luo and team:
1 - Bengal tiger (P. t. tigris) - India, Nepal, Buthan, Bangladesh.
2 - Indochina tiger (P. t. corbetti) - Thailand, Myanmar.
3 - Malayan tiger (P. t. jacksoni) - Malaysia.
4 - South China tiger (P. t. amoyensis) - South China, South Africa (!).
5 - Sumatran tiger (P. t. sumatrae) - Sumatra, Java/Bali (?).
6 - Amur/Caspian tiger (P. t. virgata) - Russian Far East.


These groups are already separated in the wild and also in captivty, so I see no reason to endanger these populations for unnecesary mixes and also there is no need to use the previous clasification of only "two subspcies" to justificate the breeding of mixed tigers in the American continent, as they serve no porpuse of conservation.



Conclusion:
the scenario of only "two subspecies" was probably correct, when the populations of tigers were interconected and the morphological evidence support that. However at 2019, that scenarion no longer exist and the populations are so fragmented that there is no logic in changing the number of subspecies when there is enoght geographical differences between the populations. Probably and if we hope the best, then the populations of tigers in Myanmar start breading again, the normal process of intermix with the Indian population will began again without human intervention. I think that at 2019, the scenario of "six subspecies" is the best to follow.

I will like to read this paper from 2018, in order to see if the Sundarbans tigers were included in the analysis of not. Like I said before, the last genetic study by Singh et al. (2015) proposed the Sundatrbans tigers like a “evolutionarily significant unit” (ESU) following the adaptive evolutionary conservation (AEC) concept, at the brink of been a subspecies of its own but not yet. It will be interesting to see the proposal of Luo et al. (2018) on this, if there is any. Reply