The male reproductive system consists of the testicles, vas deferens, epididymis, prostate, and penis. In pinnipeds, males have a bone inside their penis called a baculum. This bone is not present in cetaceans. As in females, significant life history information can be gained by careful examination of the male reproductive tract. For example, determination of whether an animal is an adult or sub-adult can be determined by looking for the presence of sperm in the epididymis and the relative size of the testicles.