Determining the Gender of Humpback Whales

Physical Differences:

Both genders have internal sex organs. The male’s  genital slit is located mid-way between the anus and the umbilical. The female’s genital slit is located in front of the anus--separated by an anatomical feature known as a hemispherical lobe. The presence  or absence of this lobe is used for gender determination in the field. 

Behavioral or Contextual Determinations

Females: On the winter grounds, it is extremely rare to find two females in a group/pod. A whale positioned toward the front of a competitive group and appears to be the “focal” point of the behavior of the other whales in the group is generally thought to be the suspected female. A solitary adult accompanying a calf is generally assumed to be a female.

Males: On the winter grounds, singers are assumed to be males. Whales involved in agonistic (competitive) exchanges such as directed lunges, fluke swipes, ramming behavior, etc. are assumed to be males.

Gender roles are not particularly associated with behavior or behavioral contexts on the summer, feeding grounds.

Other Indicators:

Body scars are helpful indicators of gender in that males tend to be more scarred than females, but one has to be very careful with this subjective method. There are many ways for females to acquire scars. However, raw chins, head nodules (raw or worn), dorsal fins, anterior edges to flukes and pectoral fins, etc. are associated with sexually mature males.

Characteristics of the North Pacific Humpback Whale

Size:

    Northern Hemisphere: Adults 45-45 feet   

    Southern Hemisphere: Adults approximately 50 feet

    Calves: roughly 12-16 feet at birth

    Record: Southern Hemisphere Female 63 feet

    Females are slightly larger than males (circa 3 feet)

Weight:

    Adults are approximately one ton per foot (length)

    Calves approximately 1.5 tons

Gestation: Estimated to be approximately one year

Migratory Species:

    Summers: Spent in northern latitudes where they feed on

                      small schooling fish and krill.

    Winters: Spent in southern, sub-tropical waters where they

                      give birth and are assumed to mate (never documented)