Questions about karma, animals, and suffering. . .
If the root cause of our suffering is our karma, what about animals? Why does nature's law dictate that one animal is food for another? Why did God create bodies that suffer pain? Who's responsible for the pain of animals? Why should they be born and suffer? Who is enjoying their suffering? Why can't God stop the suffering? If we kill a cow it is wrong but if tiger kills it is nature, but either way the cow is the one who suffers. . .
Laxmimoni dasi answers:
First, karma isn't the root cause of our suffering. The root cause of suffering is our material desire, and our ignorance of our eternal spiritual nature—thinking we are matter and that matter will make us happy. Due to that illusion (the root cause of all our suffering) we work hard to enjoy the material world, and the result is karma. Selfish actions lead to reactions, and reactions—"good" or "bad"—lead us to repeated birth and death, which leads to temporary happiness and to suffering, and the cycle goes on.
The pain of the body comes with the package. The body is matter, and matter gets old, rotten, and dies. In this way, we suffer both mentally and physically. We suffer mentally because we want to enjoy and pain gets in the way. We suffer physically because pain prevents us from doing what we what we want to, or have to do, and that also causes suffering. Yet we still attempt to enjoy—often at the expense of others, such as animals—so we get karma, for which we suffer now and in the next life.
Animals are suffering due to past karma, past material desires, stemming from their attempts to enjoy in some human body before. The animals don't generate karma though; they simply move up the evolutionary scale, undergoing birth and death until they reach the human form. Once there, the soul has choices to make. In the animal forms there are no choices. In that condition, the soul is silent—instinct alone is driving one's actions—and so there are no reactions, just upward movement until they reach the life of choices, which is human life.
That one living entity is food for another in the animal kingdom is just the law of nature in action. To be born as a cow and killed by a tiger involves suffering but no karma. Rather, it's the end of some reaction. Free of that karma, the soul can continue his journey toward human life, where conscious choice determines future suffering and/or enjoyment, and where emancipation from all suffering is possible. If they become Krishna conscious and engage in Krishna's service—which is karma-free—then there will be no more suffering and no more birth and death. When we're engaged in Krishna's service, there is no reaction, no more birth and death, and therefore no more suffering.
You ask, "Who is enjoying the suffering of the animals?" Some people enjoy eating meat. They perpetuate the killing of animals so they can "enjoy" in the present, but in the future those people will suffer in animal bodies—and perhaps get killed by a tiger or a butcher. What goes around comes around. This will continue until we leave the wheel of repeated birth and death.
I hope this is of some help.