Reproduction is not simple or easy, nor is it fair. Females often bear a larger reproductive burden of child bearing and child rearing. Reproductive strategies can be simplified into two primary strategies for males and two for females: males either engage in sperm competition or physical competition while females strategize to get resources from males, or to find the best male genes for the offspring. Rape and violence, as reproductive strategies, occur in few species, but violence is especially prevalent among the great apes, probably because eggs are so scarce in these species. In orangutans, rape is common. For gorillas, infanticide is a common form of reproductive violence, and male chimpanzees regularly fight each other and batter females.