Mating
Humpbacks
When it comes to whale mating behaviors, humpbacks are the most studied species. Depending on their exact starting location, they embark on a 3,000-5,000 mile long migration from their Northern summer feeding grounds in the poles to tropical water in the winter, this is the longest migration of any mammal. Whales that spend winters in Alaska and Northern British Colombia tend to migrate to Hawaii to breed while whales that spend the winters feeding in California tend to migrate to Mexico. Some whales will switch their breeding grounds from year to year with no clear indication as to why. Many females who already have a calf decide not to make the long migration. The females who do make it to the breeding grounds with their calf tend to have a male escort nearby who charges at other incoming males in the hopes that she will be willing to mate with him, though this is unlikely. Humpacks become sexually mature around 8 years old but they don’t usually engage in sex for another 5 years. They usually give birth about every 2 to 3 years. They are polyamorous, during mating season females are seen with multiple males. During winter breeding months they do not feed and instead live off their fat reserves. (Darling, et al 1970)
Humpback males sing songs that are thought to be used to attract females and ward off other competing males. A population of males will sing the same song with slight variances between individuals. When a female seems interested in mating there will often be groups of 3 to 20 males pursuing her. She will have a primary escort who swims close by her side. The rest of the males trail behind and occasionally challenge the main escort. These altercations can become quite violent, they might strike each other with their tail fluke, pectoral fin, or use their heads to ram into each other. The main escort may also make curtain bubbles, as pictured to the right, to confuse competitors and make them fall behind. This pursuit is known as a heat run and can last for several hours. The competition is beneficial to the female because by mating with the winner, she ensures the genetics of the strongest and fastest male. The rest of the encounter seems to be brief as the main escort does not typically stay with the same female longer than a day, parting ways to search for new mates. (Silber and Gregory 1986) No one has ever observed the whales actually doing the deed so a lot is still left to speculation. What is known is that males have a 10 ft long penis and produce extra semen during this season in an attempt to flush out the semen of other males and successfully impregnate the female. The males tend to be smaller than the females and are not involved in raising the calf. The gestation period is about 11 months and the mother will care for her calf for about a year until they separate. (Darling, et al 1970)
Watch this video to see a triad of Gray whales engage in mating behavior.
Gray Whales
Other species of whale, like the gray whale, are much less aggressive when competing for female attention. Two males will often be seen with one female, rubbing up against her in an attempt to ensure she is receptive. Instead of fighting with one another they have been seen taking turns mating with her. In this way the competition occurs internally between which of the males sperm will be the one to impregnate her. (Gibbons 2021)
Narwhal
Narwhals live in the Arctic ocean and usually migrate around 200 miles to mate during winter. Male narwhals grow tusks about 0.5-2.5 m long. Their tusks are modified teeth that grow in a spiral shape from the top of their head.They are uncommon on female narwhals and instead thought to be a form of sexual selection. Researchers have found that narwhals with longer tusks also tend to have larger testes. Though the exact function is unknown, narwhals may use their tusks to ward off and intimidate other males, to hunt, and as a sensory tool. (Rigby 2020)
