Gender ID - Cetaceans

Him or Her? Gender is one of the most important elements of the level A form and determining he or she is quite different in a cetacean than pinniped. In general, most cetaceans do not have the obvious secondary sexual characteristics such as the raised bony CREST that you find on the forehead in male California sea lions. Cetacean males also do not have a baculum, or bone in the penis, which is readily distinguishable even after extreme decomposition. Rather, body size tends to be the biggest difference between male and female cetaceans and often even this is not readily distinguishable. Thus, gender determination in cetaceans usually relies upon examination of the ventral body surface.

While there can be considerable variation between species, the main external differences between male and female cetaceans are that females have MAMMARY SLITS which flank each side of the genital slit AND females have a long external genital slit in which both the vagina and anus are located while males have separate genital and anal slits (see figure below). There can be considerable variation where the genital slit is located ventrally in male cetaceans so be sure to double check!

Often times when an animal is decomposed, the mammary slits can be hard to distinguish. If you are unsure after examining the animal visually, you can take a gloved finger and palpate the genital slit. If you find that your finger is able to penetrate with a forward (cranial) position this is a female. If your finger slides more toward the tail of the animal then it is male and you should be able to feel the penis.


 Below you will find helpful hints on gender identification in cetaceans.  CLICK on an image to see an enlarged view.

gender ID for cetaceans In this schematic of a generalized delphinid, you can see that the presence of MAMMARY SLITS flanking the genital slit and the SINGLE EXTERNAL GENITAL slit in females, which contains both the vaginal and anal openings, distinguishes females from males.
Female porpoise gender ID Can you identify the structures indicated by the arrows and black circle in this harbor porpoise? Is this a male or female?
gender ID female porpoise This is a FEMALE harbor porpoise! You can see the mammary slits on each side of the GENITAL SLIT. The anus and vagina are contained within ONE EXTERNAL GENITAL SLIT.  What would this look like if it were a male?
male porpoise Can you ID the three circled structures in this harbor porpoise? Is this a male or female?
male porpoise This is a MALE harbor porpoise and you can see that there is a SEPARATION between the genital slit and anus.
female genitals Can you tell the gender of this harbor porpoise? Although this animal is fairly decomposed you can see that there are mammary slits on each side of the genital slit. This is a FEMALE!
male genitals As you approach this animal on the beach you should immediately notice separate genital and anal slits telling you that this harbor porpoise is a MALE! Also notice that in this adult porpoise, the genital slit is quite far forward (cranial) compared to the younger animal that is shown above.
male tursiops This is a young MALE Pacific bottlenose dolphin (Tursiops truncatus). You can see that there are no mammary slits and there is a separation between the genital slit and anal slit.