Okay, I'm high...so this might not make much sense. That being said. Can genetic mutations occur that only effect social behavior? For example, can an animal that only eats fruit suddenly have a genetic change in the brain that causes them to develop a taste for meat? Or does it always just come down to environment causing that kind of social change?
If an animal runs low on one food source the only option is to migrate or look for alternative sources of food. Example, the orangutan uses a stick to open a certain fruit that would otherwise cut him because of thorns. So sometimes, instead of migrating or looking for other food, they develop ways to get at the food they already have but can't quite get to. I don't know of any animal that would quickly change its diet like that unless it's human. Cougars don't exactly go to their butchers or local meat market and ask for white meat for a change. I'm not sure if I really answered your question.
The type of food an animal eats is dependent upon which type of food its body is able to digest. Deer won't eat meat and lions won't eat grass. It's not a personal preference, they're just unable to live off of anything else because their body isn't adapted to converting that food into energy and nutrients.
You have to keep in mind that evolution works slowly. Veeerrrryyy slowly. It's usually not one mutation that will cause a difference in behavior, but rather several. If vegetation was scarce, then biological functions allowing the organism to eat meat would have to evolve (e.g. strong jaws, a proper digestive system, and yes, a neuropsychological desire to hunt and eat prey).
Pandas live on nothing but bamboo shoots, but it isn't their natural source of food, they just choose to eat it. MelT
No. Humans could live on cookies, but it's not our natural food, we're omnivores who need a broad range of foods. Horses can live on dates, and though their natural food is grass, some will still choose dates over grass. Pandas choose to eat bamboo because it's sweet, and requires no catching - and their choice is fast becoming a part of their downfall. I also seem to remember that Koalas choose to eat eucalyptus, though again it's not in their natural diet. Must check that out though... MelT
I've heard that Koalas eat eucalyptus because it induces a high like state. I've also read before that some animals will eat psychedelic mushrooms and also trip off them; some of the animals would not even normally eat mushrooms. I'm not sure how true those claims are, but I wouldn't be too surprised if they were.
Some animals enjoy as good trip as much as we do. Further evidence that we are not so different from the rest of the life we encounter on this planet!
An article that addresses the OP question. http://www.nytimes.com/2007/06/26/science/26essay.html/&ex=4b8a9fb524c99cdd&ei=5070 Some researchers are finding that natural selection isn't the only driving force behind evolution.
while this is very close, it shuld be slighlty re-worded when theres an extreme situation (whether heat, or food/water shortage) the biological functions dont really evolve for the individual animal. The mutation already exists its just not being used. If a few individuals have some mutation that allows them to store water more efficiently, they will survive and reproduce. If there were no mutations such as this, the species wouldnt force an evolution, it would die.
If we're talking about a sudden event, then you're definitely right. I was talking about a gradual dwindling of food supplies, but I wasn't clear.