Extinction Peeve

[arcticpenguin]

Bigger is an adaptation for a particular environment = short term success.

Smaller is more flexible when the environment changes = longer term success.

In a similar vein, generalists do better in the long term than specialists. For example, if a predator adapted itself to be exquisitely good at catching one particular type of pray, that means short term success, but may be a liability in the long term.

 

[Eos of the Eons]

Yeah, look at Koalas-they only eat Eucalyptus. If it's bye bye Euc trees, then it's bye bye Koala. Same with animals with only one type of prey. The more junk you can eat, the better your survival. Have you seen all the crap they've found in shark stomachs? Or crocodiles too. The smaller you are, the less you need to keep going.

Trouble there is...I'm short, and can't eat as much as tall person. Sigh. Fat is a factor. That's a plus in nature though. A fat mouse will get farther than a skinny one. I don't think mice care if their mate is nice and chubby

 

[jimlintott]

They respected nature and tried to avoid waste. Spear a few, let the rest go, you know. Unless someone has proof otherwise.

Actually I wonder if you have any evidence that this is true?

Even today natives are bad for overhunting and fishing. Native over hunting and fishing is constantly a hurdle to wildlife conservationists. Anectodally, I know natives who hunt caribou. They know when the migrating herds will be through and they kill as many as possible. A friend of mine who lived in Iqaluit said that whenever beluga whales came through that the villagers would shoot as many as possible.

Now I know that anectodes don't constitute real evidence but consider it from a practical survival point of view. Did natives set out quotas before a hunt (which would be something they no longer do) or did they at some point during a hunt declare that they had enough and stop? This makes no sense. What does make sense is to kill as much as possible. Even then there is no guarantee that they had enough. With primitive weapons they likely could not threaten an animal's population. Kill as many as possible is the best strategy for survival. As someone pointed out, evidence of dead prey that was untouched suggest that this strategy was used.

Sure the natives didn't waste much. When times are tough and hard you can't afford waste. Of course natives lived in harmony with nature, they had no other choice. (Actually we have no other choice either but seem to ignore that. It will get us in the end.)

 

[neutrino_cannon]

OK arcticpenguin, no significant numbers of brown tree snakes have gotten into hawaii.


The mammoths do share a common ancestor with the elephants, probably a very close one, but they exploited an entirely different mode of life. The rhinos cleodonta and elsmotherium were related to today's living rhinos (which had evolved by the pleistocene) but they're not that related.

The reason that so many animals got large during the ice ages is that large animals conserve heat better than small ones. Again, with the patchwork of ecosystem, rather than wide bands of them it was eaier for large, less adaptable animals to find a niche.

Blizkreig hypothesis states that human populations would have exploded after finding large populations of easily hunted, slowly reproducing prey, meaning that even if they were eating fairly efficiently, there would be no way for the populations to recover. Certainly the diprotodonts of australia (essentially very very large wombats) would have been completely defenseless, and very slow reproducers. Large marsupials in australia were almost completely eradicated, present species of kangaroos and kin representing only a fraction of the biodeversity that once lived there.

Extensive kill sites, along with the fact that all the large (cow and over sized wombats, among others) went extinct, along with a large varanid and a ratite when humans arrived means that people are almost certainly to blame for australia's heavy losses.

 

[Eos of the Eons]

Kind of joking here...but are we to blame that they were slow producing and easy to kill?

I'm sure other predators that arrived around or before the time humans did have to contribute to their extinctions too.

Survival of the fittest.

 

[Correa Neto]

Some points-

(1) The flexible or generalistic species are those most likely to survive and prosper after an environmental change or the introduction of new species (if, of course the new species is not also a generalist). Large animals tend to be more speciallized (note the gliph in the word tend). Dinos gone away, while crocs, snakes, turtles, lizzards, birds and small mammals survived. All of these are resistant, fast-breeding (or with a large offspring), small (except for the crocs) and generalistic or oportunistic (in terms of food) species.

(2) Here in South America threre were also giant crocodillians in the Pleistocene. Why they got extincted? No more big prey, quite likely the same thing that affected the smilodons. Both species hunted using ambush strategies. A smilodon probably was not able to chase its prey for a long time (just look at a smilodon skeleton- heavy, truly massive bones). They probably ambushed large slow animals, and would not be succesful against fast game such as deer.

(3) The introduction of a new predator can only be responsible for exctinction of a species under certain circunstances. Fast-breeding predators whose increase in population does not follow the rate of breeding of its prey is an example. Is predator and prey evolve toghether, then in most cases a ballance is achieved. But when the new predator species is introducted on a new environment, say after a land bridge is formed, the story may be different.

(4) When a land bridge linked South an North Americas, South America's large marsupials were extincted, possibly due to the introduction of new predators (felines). But, large carnivorous birds from South America used the same bridge to colonize North America. They found a new niche there. This shows that every case is a case.

(5) Beside giant crocs, we also had large monkeys, giant sloths horses, bears and other animals. They all vanished roughly at the same time that the last Ice Age ended and man reached South America. The introduction of this new predator certanly affected the ecosystem, and may have been the last drop for many species.

 

[fishbob]

In a similar vein, generalists do better in the long term than specialists.

Humans are a real good example of generalists - we can survive quite nicely on almost anything.

The introduction of a new predator can only be responsible for exctinction of a species under certain circunstances.

The new predator can also wipe out the food supply of other predators and help drive the other predators towards extinction.

The interrelationships between the components of an eco-system are very complex. The difference between humans and other predators is that we can work at figuring out some of these relationships.