Buddhism vs. Nature and Real World I'm not very experienced in Buddhism but while reading some articles and few books about it I wonder about one key thing..

If I am not mistaken, the compassion with other species is one of the key pillar of Buddhism. It teaches us that everything is relative and feeling the compassion with others can help us from the anger and so on (perhaps it's very vague claim and I know there's much more to add but to keep this question brief..)

I really do like the idea however I'm "lost" when it comes to confrontation with laws of nature. Biologically, the human is just an animal. Everyone is trying to survive. The stronger eats weaker (we see it in nature every day and every second - tigers, sharks..everyone just hunts for weaker in order to feed itself and survive). I mean - where is the compassion here? 

When I look around and think of the nature I can't help my self but - it's brutal. For example, what about an elephant stepping over the mouse without even realizing it just killed the poor mouse? Or bird mommy flying out of the nest to find some food for the young ones and getting caught by cat? The young birds will die brutally by hunger..and nature has millions such examples every day. Technically, the mouse will die because it wasn't strong/fast enough to escape. The same for those birds. That's how nature gets rid of the weaker ones. It's brutal. The morality and ethics teaches us to value the life while in fact the nature seems to possess no value for life.

These days, we, the humans can simply call a pizza service and feed ourself. It is the science and technology allowing us to survive the harsh conditions. The development of our civilization. But the core is the same - the struggle for survival where the compassion doesn't really help much. How can I possess a compassion to someone who tries to kill/eat me? 

Maybe I am wrong. Maybe this question doesn't have any sense. But still - I'd like to ask you - does the Buddhism say anything on this topic?
Samsara can be quite brutal and there is suffering. The Buddha acknowledged this in the First Noble Truth. And his last words urged his disciples to strive on with diligence toward their enlightenment. Only through Nibbanna will one escape the suffering of Samsara.

Nature is full of examples of suffering such as you detailed. The animals involved have no evil intentions. They simply eat to stay alive. This is why humans are so very fortunate. We generally don't have to live such a brutal life and we can think things through and form intentions and take actions with as much wisdom and compassion as we possess. This is a blessing.

Treating all beings with metta (loving kindness) creates peace in one's mind. Treating other beings with cruelty creates conflict and discord in one's mind. One is clearly better than the other for living a peaceful life and for creating better conditions for one's meditation and eventual enlightenment. 

A sutta which explains this idea of taking care of others by taking care of yourself is the Sedaka Sutta. SN47