HUMPBACK WHALE BREEDING BEHAVIOR
Every winter, thousands of humpback whales from the North Pacific migrate to the waters off Hawaii for two reasons: to mate and to give birth.
This Hawaiian assemblage is one of the largest known aggregations of humpbacks with an estimated 10-12,000 humpbacks, or 50% of the North Pacific population, migrating here each winter. The calm, clear waters of the Maui Nui channel make this the ideal place to study humpback whale breeding behavior.
The Female Humpback: The Lynchpin of Reproduction
In the mid to late 1990s, our team discovered that humpback whale singing was not directly attracting females (as it was then presumed), but rather singers attracted other lone males. This led Whale Trust researchers to question the role of females on the breeding grounds. It seemed that we were missing half the picture of what occurs here! So, Whale Trust started investigating male-female interactions and how these interactions are influenced by female reproductive status. \
HUMPBACK WHALE Mating, BIRTH & Calving
Do these different female reproductive objectives lead to different interactions between males and females?
Female humpback behavior patterns in Hawaii fall into two realms: mating and calving (giving birth, newborn care). But do these seemingly different reproductive objectives lead to differences in how a female responds to and interacts with a male?
To test this hypothesis, we tracked and followed females both with and without a calf to see what a day in the life of a female humpback was like. We recorded their movements, behaviors, social interactions, measured their body size and that of their male companion, and played back sounds produced by males in multiple-male, surface active groups to see whether or not females responded differently to males based on the female’s reproductive status.
Our results showed that female reproductive status was indeed an important consideration in understanding and interpreting female behavior on the breeding grounds, especially around males. But we were limited in how much we could say since virtually nothing was known about how reproductive hormones impacted female humpback behavior. Current studies are focused on 1) investigating the status of reproductive hormones in subject females within social groups, and 2) documenting reproductive behaviors of subject females on the Hawaiian breeding grounds. Visit our Current Research page to learn more.
KEY FINDINGS
- Social groups of humpbacks do not always contain a sexually mature male and female, but may reflect a variety of age and gender combinations. For example, pairs may be male-male, adult male-female, adult male-subadult female.1
- Individuals within male-female groups may use a variety of tactics when pursuing or interacting with each other. For example, smaller males may harass smaller, and presumably younger and less experienced, females with calves, as well as juvenile females.1
- Female humpbacks may use acoustic cues to avoid interactions with males on the breeding grounds.1
- “Breath-holding” pairs on breeding grounds are male-female pairs and can be together at the beginning or ending of surface-active groups.1
- The male production and female reception of bubbles suggest that bubbles may also play a role in courtship, mating.2
- Results of playback experiments and behavioral observations both showed that mothers with calves avoided males on breeding grounds more than females without calves.1
- Females may also use different tactics to avoid males (e.g., “rubbing off an unwanted escort” on another nearby female group).1
- Singers accompanying females is relatively rare [need to find out if its 1 in 10]. However, females with calves are more likely to be accompanied by a male singer than females without calves, further suggesting that singing does not play a role in mating or courtship.1,3
- Like other female mammals with offspring, humpback whale mothers may conflict with breeding males that stand to maximize reproductive success by increasing access to receptive females. 25% of females and calves on the Hawaiian breeding grounds were actively chased by lone males.1
Reference
- Jones, Meagan E. 2010. Female Humpback Whale (Megaptera novaeangliae) Reproductive Class and Male-Female Interactions during the Breeding Season. Antioch University, New England. 184 pp. (Download PDF)
- Jones, M.E., Nicklin, C.P., and Darling, J.D. 2022. Female Humpback (Megaptera novaeangliae) Whale Positions Genital-Mammary Area to Intercept Bubbles Emitted by Males on the Hawaiian Breeding Grounds. Aquatic Mammals. 48(6), 617-620. (Download PDF)
- Darling, J.D., Jones, M.E., and Nicklin, C.F. 2006. Humpback Whale Songs: Do they organize males on the breeding grounds? Behaviour. 143: 1051-1101. (Download PDF)