That's the definition of life on this planet. Altruism is also a survival strategy, but only under limited circumstances. Meanwhile...
That's the thing that always gets me about peope who say that we Humans are somehow so much worse than other animals, that we are horrible creatures, etc. etc.
We probably really, really aren't any worse than them on principle. We animals on earth are all driven by the same basic instincts and basic urges that hit humans just as hard as any other species.* We humans didn't invent greed, envy, hate, jealousy, the urge to grab every resource we can, or the urge to remove anything that threatens us, if we *can*.
The difference is that we have developed the *means* to drop bombs and build factories and turns areas of land into parking lots and barren fields for our own resource and territory gains. If they had the same possibilities, they'd very probably roll like we do, simply based on the fact that we're all part of the same self-perpetuating cell-divison and reproducton that is evolving all around the planet. It's just that we like to romanticize the whole us vs. other animals situation.
We are simply the branch that has spun out of control in its capabilities due to said evolution, and that's the out-of-control difference.
The really, really sad thing is that we also developed the capability for rationally thinking about consequences, and you'd think that would makes us just stop. That would be nice.
But the reality is: The very same urge and instinct that stops each and everyone of us, me, you, right now from just passing on 95% of our belongings not necessary for survial, not using heating or warm water unless it's necessary for bare survival, never fucking again, and just tending to a pile veggies and trees for bare self-reliance is the very same set of urges and instincts that keeps everything hurling towards collapse at a large scale.
* Except the goddamn Capybaras. They are like the Dalei Lamas of the animal world.