MadSci Network: Evolution
Query:

Re: What is the survival advantage of the solitary behavior of tigers?

Date: Mon Oct 25 17:54:09 2004
Posted By: Brian Foley, Molecular Genetics Staff Scientist
Area of science: Evolution
ID: 1098653025.Ev
Message:

Not everything alive today competes with every other living thing for the "survival of the fittest". If we must reduce all of Darwin's observations and writings to a single "sound bite", it might be much more often accurate to use "elimination of the weakest" rather than "survival of the fittest". Lions compete with other lions much more than they compete with tigers in the same habitat, and they don't compete at all with Arctic wolves. Wolves compete against other wolves more than against arctic foxes, coyotes or lynx. On top of this, lions and tigers do not often share the same habitat. Lions are mostly grasslands predators while tigers are predators of forests and jungles, and as such, they may be equally more fit than the other at filling their respective niches.

A lion in a pride may have an advantage over a solitary lion, but that has more to do with the other lions being willing to cooperate, than anything else. The individual lion or tiger can't really choose to live in a pride or solitary, it takes willingness on the part of the other members of the species. It is quite likely that pack vs. solitary hunting is controlled more by social or learned behaviors than purely by genes. Wolves do some hunting as a group and some as solitary animals depending on seasons and the prey being hunted among other things. Likewise, since the prey available to tigers and lions are so different, they use different strategies to hunt them.

If it were true that survival of the fittest was the rule, and that all species competed, then we would most likely see just one super predator on earth. Instead we see not only bears, cats, wolves, raptors, scorpions, spiders and hundreds of other predatory classes of animals, but we also see dozens to tens of thousands of species within each predatory class. There are over 2,500 species of scorpions, for example, and at least several dozen cat species.

We observe increasing diversity and specialization into niches not only in biological evolution, but also in human social evolution. Where there were once just a few types of people in a tribe or community, such as the medicine man, the hunters and the basket weavers, we now observe thousands of professions being practiced in most cities. Where we once had basically one automobile being produced in America, we now observe a single automaker such as Ford producing at least dozens of different models each for a different niche market. The Ford Explorer certainly does not compete with the Cooper Mini for the "fittest" auto. Nor does a banker compete with a film maker for the "fittest" worker. The attributes that contribute to fitness in each one's niche are often unneccessary or detrimental in the other's niche.

It is possible that there have been lions that went off to live solitary lives and they never survived. It is equally likely that lion-like cats which went off to live alone did survive and evolve into something like tigers. At one time in the very distant past there was once just one cat-like mammal that was the ancestor of all the felines that survive today. It was fit enough to survive, and so were all of the individuals in between that ancestor and today's cats. There were almost certainly even more individuals and groups, such as the Saber-toothed tiger, that did not survive to the present. If the saber-toothed tiger had migrated to Africa to hunt elephants before humans had killed off the last of the Wooly mammoths, it might be alive today. But not all species get to try out all niches.

All species alive today have survived equally long. Species change morphological shapes at different rates. For example many ants alive today look exactly like ants that were alive over a hundred million years ago, while many beetles and other insects can dramatically alter their morphology in just a few million years. Yet the DNA of both the beetles and the ants have evolved at nearly the same rate. This has to do with different types of selection pressures being the driving forces behind the evolution of different types of organisms.

To humans, all wolves look pretty similar, and most people would guess that a wolf is more closely related to a coyote than a Saint Bernard domestic dog is related to a Dachshund domestic dog. But DNA evidence plus breeding records and human archeological remains all tell us that domestic dogs are all very much more closely related to each other than wolves from different regions of the arctic are related to each other, and the distance from wolves to coyotes huge in comparison to either of those distances. The morphology of canines is not an accurate indicator of evolutionary time. Human selective breeding of dogs is a very different evolutionary selection pressure than the natural selection in wolf packs.

So there is really no way to compare the "fitness" of the lifestyle of lions to the "fitness" of the lifestyle of tigers. Such a comparison is similar to comparing the fitness of grasses to the fitness of trees. Each is fit enough to survive in its own niche and not go extinct, and each may sometimes compete against and sometimes cooperate with the other.

Another factor that is often overlooked in the study of evolution is selection by microorganisms such as viruses, fungi and bacteria. A pride of lions might be able to out-hunt solitary tigers by over a hundred fold. But if a virus or other pathogen spreads from lion to lion within a pride a thousand times faster than it spreads from solitary tiger to solitary tiger, then the tigers may gain a huge advantage over the lions, which most field biologists would never detect.


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