All forms of Altruism in nature can be actually interpreted as inherently selfish. For example:
A bee who stings an attacker: It may seem as though that when a bee does this he is putting his life on the line to protect the hive. However, the bee himself does not know that he will die when he attacks. His attacks are instinctual. They are essentially a reflex. He attacks a predator believing that he will emerge unscathed with his genes protected. However the fact that he doesn't know doesn't prevent the act from being altruistic. It's just the fact that it was unintentional altruism that prevents it from being a "well-intentioned act".
A bird that sounds an alarm to warn other birds of predators: This seems like a perfectly sound argument to inherent altruism. However, usually, birds that sound the alarm to other birds are actually the mothers. They are warning their children. Their gene spawns. Warning other birds is a byproduct of this.
A penguin that jumps into the water first to check for predatory seals: He is pushed in. Enough said.
Walruses that take orphans. Whenever a walrus might be in trouble, I'll bet my hat that he would sacrifice the walrus he adopted if it meant that his children and he would be saved.
Now let's observe some cannibalistic behavior in animals that are anti-altruistic:
Seagulls tend to trick other seagulls to look away so they can eat the chicks of said seagull in order to avoid looking for fish in the ocean and putting themselves in danger.
Female Praying Mantises eat the heads of their partner during mating because there are nerves in the head of the male that act as neural inhibitors that keep the male from performing better in sex. Once those inhibitors are gone (i.e. eaten) the female would experience a MUCH better sexual experience. The nutritional value that could be derived from this is unknown to the mantis. She's just hungry. Sex is a lot of work - I would be hungry during it too. All she knows is that it feels good to eat his head.
There are also cases of blatant homocide towards children in animal species. A lion, for instance, would kill and eat the kin of another lion in order to enhance the probability that his child will reproduce with a lioness in the future. This is done so the individual lion's genes are passed on. The genes that are in the lion, which copied themselves to the child will copy themselves again and continue their immortal lives.
Also donating to charity is not an act of altruism because it is done in order to make you feel better about yourself and to help fix the world in order to make it the way you want it.