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(11-15-2014, 08:29 PM)'GuateGojira' Wrote: This point has been discussed before en AVA, and at this point, Peter was the only giving a large explanation.
From my point of view, the explanation is very easy and has nothing to do with genetic or subspecies, but with feeding and care.
All captive Amur tigers live in "first world" countries, especially those on the Studbook. They had been kept in the best conditions since the beginning of they captivity and they form part of the first program to conserve tigers worldwide. At this moment, is the most safe population in captivity with an optimum number and great care.
On the other hand, Bengal tigers have a doubt origin, and except those from India, all, I mean ALL captive "Bengal" tigers in the Earth are not pure, but hybrids with other species. The thing is even worst, in the old days, Indochina tigers were also included in this subspecies, so the intermix of this groups was normal and frequent. At this day, only Bengal tigers from India are 100% pure and represent the only population available for conservation, however, the studbook is very recent (about 2010, as far I remember) and the conditions of the Indian zoos were deplorable in most of the cases.
Now, with this fact established, we can see that the Amur tiger live in a "paradise", compared with Bengal tigers, and like in humans, individuals living in better conditions develop much better than those in poor ones. The last document about captive specimens put an average figure of 183.3 kg (range 165 - 210 kg) for 16 captive male tigers and 134.6 kg (no range) for 5 female tigers, all in India (Sontakke et al., 2009; Slaght et al., 2005).
On the other hand, Slaght et al. (2005) present an average weight of 169 kg (n=39, no range) for male and 124 kg (n=53, no range) for female captive Amur tigers (248 kg the maximum figure), however he included young and several unhealthy males, like a c.12 years old male of 110 kg and a c.20 years old male of 120 kg. This figures should be excluded, as the produced range is unreliable.
I collected 24 male and 13 female captive Amur tigers from scientific documents and reliable sources and I get average figures of 212.5 +/- 36.28 kg (n=23. Range: 167 – 306.5 kg) for males and 127.3 +/- 14.02 kg (n=13. Range: 113.4 – 158.8 kg) for females. Tigerluver included other specimens to this list and gathered a higher average figure.
At the end, I think that the differences in captive specimens are not about genetic of subspecies, but about correct breeding, enough food and good facilities. In good conditions, captive Bengal tigers will also develop the great sizes than they wild counterparts. The last time, I remember an Indian tiger in captivity named Raja, that at his 12 years old weigh 280 kg.
In conclusion, a correct comparison between captive specimens will never been correct, unless than the conditions would be standardized between all of them.
Still, the only modern cat in the captivity that is capable to reach the size of the largest fossil felids is the Amur tiger.
Which i still insist the multiple origins of the modern Amur tiger population. Just like the human species, the modern tiger population could also be likely the result of the hybridization of several ancient tiger populations.
Amur and Kaziranga Tigers - Habitat and Prey Analysis
