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

[peter]

PC

A century ago, male tigers in northeastern India were 2-5 inches shorter than males in northwestern India and western and central Nepal. It is a fact that males shot in northeastern India were a bit heavier than those shot in the northwest, but there are good reasons to assume that tigers in northwestern India and Nepal most probably were heavier than those shot in the northeast. 

The tigers weighed by the Maharajah of Cooch Behar were about an inch longer than those not weighed. They were also about an inch longer than those weighed by Hewett in the northwest. Those not weighed in northwestern India, however, were significantly longer than those weighed (about 3,5 inches). Based on the correlation between total length and weight, I concluded that male tigers in northwestern India and western and central Nepal most probably would have outweighed male tigers in northeastern India. If all male tigers would had been weighed in the regions mentioned, the average for northeastern India would have been 450-460 lbs., whereas male tigers in northwestern India would have been ranging between 460-490 lbs. Nepal male tigers, ranging between 480-500 lbs., most probably would have topped the table.

These conclusions, of course, have a speculative character, but it's the best I could do with the information at hand. This was in a period of nearly unrestricted gene flow. My guess is things didn't really change in the last century. The reason is the ecosystems, although more fragmented and smaller, still are largely intact.   

Today's tigers, if anything, seem to be heavier than a century ago, but I wonder if the fundamentals changed. Tigers in northeastern India (Kaziranga included) could be a bit shorter than those in northwestern India and Nepal. The photographs of Kaziranga tigers I saw very often show quite massive and well-marked animals with large and wide skulls, whereas those in northwestern India seem to be longer, taller and a bit more athletic. Based on my experience with captive animals, they could be a bit underestimated.

But I could be wrong. In nearly every book about Assam I read, tigers were described as bulky and heavy animals. Experienced observers and hunters agreed that prime males often would have been close to 600 lbs. a century ago. These observations were dismissed, but the information on today's tigers strongly suggest that they could have been closer than many assume. 


Shardul

I hope the new thread your started ('The Terai Tiger') will develop into a good one. The topic is interesting and so is the information posted. Do you have more on the different landscapes and in what way they affect tigers? 

The feedback on my post on the Terai Arc Landscape was appreciated. I agree I should have spent a bit more time on reading before writing the post, but I was very eager to do the post. The reason is the information I have strongly suggests there is a connection between ecosystems and tigers.

Here's a few remarks on the points you made.

Ad 1 - You are right. The map shows the whole Terai Arc Landscape, not just the Indian side.

Ad 2 - Map d3 in my previous post says that Kumaon was part of the former Gorkha (Ghurka) Empire until 1815. If Nepal is seen as a, limited, continuation of the Gorkha Empire, one could say Kumaon was a part of what is now Nepal until 1815.

Ad 3 - I don't remember positioning Chitwan in the heart of the TAL in my previous post. Chitwan is in the heart of Nepal and, as you said, in the extreme east of the Terai Arc Landscape. I'm not sure as to what you mean, but assume you referred to two remarks that seem to contradict each other.   

I wrote Chitwan male tigers (in the extreme east of the TAL) are unsurpassed in total length (a). I also wrote the extreme northwest of the TAL could have had the largest tigers (b). These remarks seem to contradict each other and could have resulted in your conclusion. Am I right?

If so, than be sure they don't. 

In books not written by British hunters, tigers inhabiting the extreme northwest of India were considered as the largest. This conclusion was based on the experience of those who had seen tigers in different parts of India, the Caspian region, Manchuria and southeast Asia. 

British hunters who wrote about their experiences agreed that the northwestern part of British India produced the largest tigers. These hunters also were aware of the size of Nepal tigers. Some of the tigers they shot exceeded Nepal tigers in both lengh and bulk. The problem is they only shot a few. Samplesizewise, the information can't be used for tables. This is not true for Nepal tigers.

Different hunters published records of all tigers they shot and measured. The result is we are able to get an idea about the size of tigers in different parts of Nepal and northwestern India. Of all regions with decent samples, Nepal tops the list. Tigers in the extreme northwest of what is now called the TAL, however, could have been similar in size or larger. 

Ad 4 - True if you want to consider data in peer-reviewed documents only, but not true if you include hunter records.

Ad 5 - True to an extent, but there is a difference in animals hunted by tigers in both regions. Based on what they hunt, I expected Kaziranga tigers to be larger and heavier than Nepal tigers. The tables I posted suggest they were not. My guess is things didn't change in the last century, but that's just an opinion. We just don't know. 

Based on what I saw, Chitwan and Kaziranga they seem to be quite different. The difference, I think, can't be attributed to food only. There's something else. Tigers in the Terai Arc Landscape could be descendants of an older wave. If they are not, they perhaps adjusted to different conditions. Tigers in northeastern India seem to be jungle animals. Those in the northwest inhabit more elevated regions. Same for Bhutan tigers and they too seem different from Assam tigers.       

Ad 6 - Hunter records strongly suggest that tigers in some parts of the western Ghats always were quite large. Those shot in Wynaad, however, often markedly smaller. Many male tigers shot in that region didn't exceed 9.6 in total length 'over curves'. In other parts, they not seldom exceeded 10 feet and 500 lbs. A century ago, Ghats tigers were larger than anywhere else in southern India. My guess is they still are. The western Ghats still is a hotspot and hotspots always produce large animals. The greater the distance to a hotspot, the smaller the tiger.    

Ad 7 - Agreed. Swampy grasslands attract large herbivores and tigers hunting large herbivores are large everywhere in Asia.

Ad 8 - When gene flow is restricted, populations become isolated. It is known that tigers living in isolated pockets tend to decrease in size. This is especially true when the region decreases in size and the tiger population decreases.

Hunting pressure should also be considered. Pressure results in fewer large individuals on one hand and in empty forests on the other. This can only result in smaller tigers in the long run. In regions were hunting was limited or not allowed, the size of tigers didn't change. Nepal is an example, but Malaysia, Vietnam and Indonesia produced similar results.

When Sumatra still was largely unexplored, hunters often were quite amazed at the size of some tigers. One hunter had been in (southern) India as well. He shot and measured tigers and also saw tigers shot and measured by others. He wrote that Indian tigers usually were longer, but not in head and body length. Most Sumatran tigers roughly compared to Indian tigers in weight, but the heaviest he saw were shot in (northern) Sumatra (Atjeh). Most male tigers he shot were 170-180 cm. in head and body, but some well exceeded 200 cm. (measured 'over curves'). This was just a little over a century ago. Today's Sumatran tigers (males) seldom exceed 8.0 in total length 'over curves' and 330 lbs.

The skulls I saw also suggest a change that resulted in smaller animals. Skulls collected before, say, 1900, often were larger and, especially, more massive than those collected between 1900-1950. Skulls well exceeding the average in that period often were from animals shot in isolated regions.          

In some parts of India and Nepal, ecosystems have disappeared. In other regions, they are largely intact. The size of tigers in these regions didn't change. Indian and Nepal tigers, if anything, now seem a bit longer and heavier than a century ago. The reason is they were going downhill nearly everywhere a century ago, whereas quite many today live in well-stocked and protected reserves. Reply