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

[peter]

Vinod\ dateline='\'1415512240' Wrote:

peter\ dateline='\'1415448877' Wrote: THE RELATION BETWEEN TIGER SIZE AND HERBIVORE SIZE

The only tigers that seem to be in the same league today, I think, are those living in north-east India. The difference with other tiger regions is north-east India is the only place where tigers still live next to very large herbivores. In contrast to what many think, some of these tigers really specialize on some of these big herbivores. Immatures are targeted mostly, but adults also are killed at times. This, I think, could explain why some of the Pleistocene tigers were large animals: the larger the herbivores, the larger the tiger. One could say large size probably was a result of plenty of food, but I think tigers really hunted large herbivores. They still do in north-east India.

Any proof? No. But there is circumstantial evidence. The bison-hunting wolves in Canada are larger than anywhere else. Brown bears feasting on salmon in coastal regions are larger than relatives living in other regions. Polar bears are the largest of all bears. Proteine no doubt is the drive in size, but that doesn't mean predators feasting on large animals are scavengers. The extra size they have is a result of hunting large animals, I think. Protein is a deceiving factor, that is. 

as far as tigers in India are concerned the largest prey they can hunt are the wild buffs, gaurs, young elephants & rhinos, Kaziranga has all of em so it can be concluded that mebbe hunting these large animals has made the tigers here bigger but you'd find similar large herbivores even in Bandipur in southern India & the tigers there are no where near the size of even a central Indian tiger.

Largest herbivore in Panna is I think a sambhar dear, how do you explain the size of Madla & even biggeer Hairyfoot?

I think terrirtorial competitiveness could also be playing a part here, bigger male the better? generally we've seen larger males rule the roost. 

a - TIGERS IN CENTRAL AND SOUTH INDIA

Agreed on most points made, but not on the alleged difference in size between south and central India tigers. The measurements I have suggest there were distinct differences between south-east and south-west India a century ago. If we include the Deccan as part of south India, we could distinguish between three regions. 

A century ago, male tigers exceeding 9.0 straight and 400 pounds were uncommon in south-east India and the Deccan, but not in the Western Ghats. Tigers in central India were a bit longer and heavier, but not by much. Central India probably had more exceptional animals. We know, because those who wrote books preferred to hunt in central India. Most of them reported about exceptional tigers. Same for Dunbar Brander. In spite of the six very large males he shot or saw shot, his average was just about 9.3 for 42 males, meaning most probably were just below that mark. Same for weight. Most males probably didn't reach 420 pounds.   

There are not that many reports on the size of tigers in south India, because it wasn't as accessible as central India. Those who hunted in the south, like in central India, often reported on large animals. Although they were there, tigers in south India were a bit shorter and not as heavy. In some regions, tigers exceeding 9 feet straight were considered large.   

The main reasons central India had more large animals were numbers and, as Tigerluver suggested, cattle. Many males of 500 pounds and over were confirmed cattle killers and well past their prime. Some of these, when the supply was cut short, moved to humans. Typical game killers were very similar to game killers in other parts of India.


b - TIGERS IN NORTH INDIA

Tigers in north India often were a bit longer and heavier than those in central and south India. After reading all recent articles on tiger evolution, I concluded it is possible India could have had two waves of tigers. The first wave settled in central and southern India, whereas the second wave entered India a few thousand years later just south of the Himalayas.

The second wave tigers could have been a bit larger. When they entered India, the melting ice and better conditions resulted in more prey animals, especially in regions close to mountains.  

Is the larger size of tigers in north India confirmed in today's measurements and weights? Yes. Do tigers in north India still enjoy somewhat better conditions? Again affirmative.   
 

c - TIGER SIZE AND PREY

As for size and reasons. You have a point in that some well-stocked regions produce tigers of moderate size, whereas others have large animals only. There is no easy explanation. It could have been a result of large prey animals all year round, it could have been a result of competition in smallish reserves with zero possibilities for dispersal, it could have been water, it could have been Bergmann's rule and it could have been a combination of factors.

For what it's worth. Large male tigers in north-east India hunt large herbivores all year round. Every large kill enables a large male tiger to use his energy for something else. Maybe they use it to route competitors and mate more often than smaller males. If so, chances are the region will produce more large tigers in the end. This process continues until the limit has been reached.

The limit could be the ability to hunt. Male tigers, unlike male brown bears, are true carnivores. At 500 pounds and over, chances are they wouldn't hunt deer for the simple reason it, energywise, doesn't pay. A wild buffalo or an immature elephant or rhino, however, would. If the supply is ok all year round, chances are male tigers will develop into specialists. This will enable them to continue the arms race, which will result in larger tigers. Large prey animals are, I think, the reason Assam tigers are and remain large. But they were enabled to get there because of the supply, so it works both ways. 


d - THE DISADVANTAGE OF LARGE SIZE IN HUNTERS

Size also can work against you. Kamsjatka male brown bears are very large animals. They could use their energy to dig up roots, but that, at their size, wouldn't do. They need protein. Apart from salmon, there isn't much of it in Kamsjatka. Not when the salmon are gone. This means they have no option but to hunt their own kind. Not cubs, but immatures of up to, say, four years or so. And an adult female every now and then. And guess what.

One could say the limit has been reached in Kamsjatka. When you start hunting and eating your own kind, the end of the line is close.


e - BERGMANN'S RULE

Apart from all that, there is Bergmann's rule. Skull and body length confirm tigers, as Kitcherner said, are a little larger in the north-east of Asia. The reason is it is colder in north-east Asia. A large body helps to conserve heat and energy. 

A long body, however, has to be fed as well. As there are no very large herbivores in north-east Asia anymore, tigers hunt deer and wild pigs. As these, as a result of the conditions, have to walk from pasture to pasture, tigers do nordic long distance walking as well. Amur tigers have large territories because they have to.

When there is a crop failure, which often happens in the north, Amur tigers, like all other animals, can't afford to go for deer and porc anymore. But bears are plentiful nearly everywhere, even in bad years.


f - TIGERS AND BEARS IN RUSSIA

The problem with bears is they know how to fight. They are very different from the very large Assam herbivores, that is. Tigers responded by hunting smaller bears, like immatures and females. They also have to be able to defend their kills from male bears, meaning they have to stand a chance in a fight with a heavier cleptocrate. According to Krechmar, they are just about able to to that. The number of male tigers displaced by male bears is very limited.  

The combined result of snow, regular crop failures, nordic long distance walking and hunting bears is interesting.

At about similar body length, Amur tigers seem more athletic than Assam tigers. Male Assam tigers are built like tanks, but male Amur tigers seldom exceed 210 kg. Assuming male Amur tigers fight dangerous opponents more often than male Assam tigers (other tigers as well as bears and wild pigs) and have just about what it needed to survive, the conclusion is a fighter in the world of big cats isn't built like a tank.

He is long and tall, has a large skull, extra-large canines and large fore-arms, but he lacks the deep chest and the bulky rump often regarded as typical for a good critter. It seems, therefore, that mass was offered for agility and some kind of endurance.

I doubt if Amur tigers would have reached the size many think they reached a century ago. Exceptional animals no doubt were there in the days of plenty, but the conditions in north-east Asia just do not allow for tigers built like tanks. Like real tiger tanks in World War Two, chances are they would get bogged down in the mud and snow. Besides, even at 500 pounds they would still need a hundred more to get to a par with an average male brown bear. The problem is you are no longer a hunter at that weight. In the conditions in Russia, you need power, but agility, speed and endurance seem as important.     


g - CONDITIONS, DEMANDS AND RESULT

Maybe the features mentioned only are effective against bears and not in fights with other tigers or lions. I heard rumours on the alleged aggression of Indian tigers from many trainers, but in the end they all agreed an average male Amur tiger has an initial advantage. The reason is they, even at a slightly larger size, are as agile and fast as other big cats.  

In the end, the size of a big cat depends on the conditions foremost. Genetics are important, but a typical hunter needs to adapt all the time as fast as he can. If he doesn't, chances are he will not make it.


h - WATER

I read nice stories about swamps, big cats and immense muscles in order to move and hunt in a way enabling a decent income.

While it is true Okavango lions and Assam tigers seem extra large and muscular, Sunderban tigers are the smallest today. The Vietnamese swamp tigers in Cochin-China a century ago also were smaller than tigers in other parts of Indochina. Sumatra also has swampy regions, but the tigers making a living over there are not as large as those in other parts of Sumatra.

The conclusion is water in itself apparently isn't a drive behind extra size in lions and tigers. Maybe swimmers are a bit more robust at times, but they are not larger. Other factors seem more important.  


i - EVOLUTION IN TIGERS AND BEARS

The factor behind size could be similar to the one in bears. Sexual drive could be the engine in both animals. Large enables more access to females, which would result in larger animals in the end.

Tigers and bears, of course, are different in that one is a typical hunter, whereas the other is not. The non-hunter, sizewise, could perhaps develop a bit more if he has a good nose and hunters he can rob, but a typical hunter can't. Unless he, as in Assam, has a year-round supply of large herbivores he's able to overcome with size foremost. Even then, however, athleticism and speed are needed to overcome resistance.

Male bears hunting large animals are not nearly as competent as tigers and the major reasons, I think, are body construction and size. Perhaps 600 pounds is the limit, but chances are it is closer to 500.

But why then are there no 500-pound male bears hunting herbivores all the time? Because they can't compete with a big cat of similar size. They don't have the weapons, the speed and the skill needed. Not enough to do it all the time everywhere. Their body evolved for robustness, probably in order to compete with other bears. Robustness and size result in digging and cleptocracy, but it wouldn't enable hunting. Even if they get experienced in hunting, they wouldn't compare to a real pro.  

So genetics it is, in the end? I would go for yes. At some stage, mammals developed into what they are today. It comes down to the basic design, so it seems.

There always are exceptions. Polar bears are brown bears who adapted to new conditions. They are the only true carnivore in their family and the reason is plenty of blubber from animals unable to move fast on the ice. In spite of their size, however, I wouldn't say they compare to true hunters like big cats. In the end, you are what you are and that will never change. The real question is why it started and moved in the way it did. The answer to that one is that the essentials regarding (the origins of) species are in the genes. You can change a lot, but not that. Reply