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

[tigerluver]

Thank you @GuateGojira for the information. With that I have been able to put together who I think this "T16" is (camera trap from 2008):

*This image is copyright of its original author

First of all, thanks to Kolchin and Maystrenko (2013), we have a second image of T16. I came to this conclusion based on the identical stripe pattern between these two pictures. Take a close look at the area circle in yellow:

*This image is copyright of its original author

The pattern is unique and identical in that region. Looking at other areas also showed a near perfect match.

Kolchin and Maystrenko (2013) detail the story of the tiger on the right, in turn detailing the story of the tiger on the left. This tiger was named Ivan, tagged as PT90. We can verifty PT90's identity as T16 via the timeline described by Kolchin and Maystrenko (2013). In mid-2008, a tiger who would later be known as Ivan (PT90) escaped its snare and attacked a researcher. At this time, the tiger lost a piece of its canine.:

*This image is copyright of its original author

This same tiger was later snared successfully in October 2009. He looked like this a couple weeks before the life-changing moment:

*This image is copyright of its original author

After the snaring, Ivan (PT90) received debilitating injuries to his left foot, emaciating him. By January 2010, he was put down after killing a human. At that point, this was all that was left of him:

*This image is copyright of its original author

Now we can verify that the 200 kg male PT90 in Miller (2012) is the same Ivan discussed by Kolchin and Mastrenko (2013) and therefore the same specimen as the mythical T16. Per Miller (2012), PT90 was captured in "fall 2009", matching Kolchin and Maystrenko's reported date of capture. He then died after human conflict in January 2010, again matching both the date and reason of death as described by Kolchin and Maystrenko (2012). We can further verify that PT90/Ivan is T16 by the note in Gilbert et al. (2015) which noted PT90 has also been described as T16 in prior reports and literature who died of "canine distemper" after tiger-human conflict. With timelines and stories from multiple sources matching each other, irrefutably the mythical T16 is PT90/Ivan. Moreover, the photo comparison above leaves no doubt.

This means T16 was weighed, and weighed 200 kg. This is quite average. However, perhaps T16/PT90/Ivan was indeed a bit more exceptional in the camera trap in 2008. T16 was weighed at the older age of 10, about a year and half after losing a canine due to the Aldrich snare. Very clearly, T16 was not as robust in 2009 as he was in 2008. Below I show a comparison of T16's mythical photo and 2009 photo:

*This image is copyright of its original author

Without any measurements, it is apparent that 2008 T16 (on the left) was bulkier. Already an older tiger and then further debilitated by the loss of a canine, T16 understandably lost mass. In this comparison photo, I scaled both photos to the same shoulder height. Shoulder height does not ideally change when mass is lost with age in quadrupeds and therefore is an appropriate tool for scaling both images to equal body frame size. At the same shoulder height, we can see that T16 had greater chest and forearm diameters in 2008 as compared to 2009. Specifically, his chest diameter was 1.12x greater and forearm antero-posterior diameter was 1.15x greater. With these ratios, we can estimate how much heavier T16 was in 2008 as compared to 2009.

I will try to explain the theoretical basis of the mathematics the best I can, but please do ask for clarification if needs. When estimating mass between two separate individuals, the individual with the larger say chest diameter should also be equally larger in length and shoulder to shoulder width (I will call this depth from hereon). This results in an scale exponent of 3. Therefore we have the equation:

Mass  specimen 1= (Chest diameter 1/chest diameter 2)^3 * mass specimen 2

However, when we are comparing diameters from the same individual, body length will not change. Theoretically, increasing the width of a muscle (sarcomere at the smaller level) should also be associated with an equal increase the depth of the muscle. The same idea is likely for adipose tissue. Therefore, the scale exponent when comparing diameter changes within the same individual should drop to 2 and the equation is as follows:

Mass  specimen at diameter 1 = (Chest diameter 1/chest diameter 2)^2 * mass specimen at diameter 2

If we apply this above equation to the measurements in the photograph, we get the following estimates for T16's 2008 mass using his 2009 mass for comparison:

Using chest diameter:

2008 mass = (184/164)^2 * 200 kg
2008 mass = 252 kg

Using forearm diameter:
2008 mass = (91/79)^2 * 200 kg
2008 mass = 265 kg

Average 2008 mass = 259 kg

Now it is possible that if a diameter increases in one direction, the diameter does not increase in the perpendicular direction. This would drop the scale factor to 1. Therefore, we have one more theoretical equation for mass estimation:

Mass  specimen at diameter 1 = (Chest diameter 1/chest diameter 2)^1 * mass specimen at diameter 2

Applying this formula, we have the following estimates:

Using chest diameter:

2008 mass = (184/164)^1 * 200 kg
2008 mass = 224 kg

Using forearm diameter:
2008 mass = (91/79)^1 * 200 kg
2008 mass = 230 kg

Average 2008 mass = 227 kg

When (vertical) chest diameter increases due increase muscle mass and adipose tissue, the chest depth probably does increase as well but not to the proportional degree of (vertical) chest diameter due to the vertical pull of gravity. Similarly, when a forearm grows in antero-posterior depth, it likely grows in lateromedial diameter as well but not to the same degree as the chest wall would limit the medial expansion of the muscle belly. Therefore, I feel the actual scale factor for estimating the weight of an individual at different diameter measurements lies between 1 and 2. If we average together the two weights in bold, we are essentially using a scale factor in the middle of 1.5. The estimated 2008 weight with a scale factor of 1.5 would thus be 243 kg. All in all, T16 was likely not 270-300 kg mythical giant, but still in his prime a large Amur tiger by modern standards.

Regardless of which scale factor one prefers, what is apparent is that the 2008 form of T16 was heavier than the 2009 form. At the least he was probably 20 kg heavier, and at the most around 60 kg heavier. Seasonal changes in body fat may in part explain the such a difference. However, Kolchin and Maystrenko's description of the damage caused by Alrich snares cannot be ignored. An old tiger already, both aging and a broken canine probably took T16's spot away as the heaviest scientifically weighed Amur tiger during the Siberian Tiger Project. By the end, his condition resulted in him losing another estimated 100 kg per Salkina (Kolchin and Maystrenko 2013). A very somber end to possibly one of the larger Amur tigers of today. Reply