What is a male Guinea pig called? Quick Answer. A male Guinea pig is often referred to as a boar. By gently pressing on the abdomen of a male Guinea pig near the genitalia, a small penis will emerge that allows you to determine the sex of your pig. Continue Reading. Male Guinea pigs are slightly larger than females, and can grow between 1.5 and 2.5 pounds as adults and can reach lengths of 8 to 10 inches. These animals are naturally gentle, can live from 4 to 8 years and are easy to care for and handle, which makes them excellent small pets.