[Photo] Each year southern hemisphere humpback whales visit the area to mate, give birth, raise young, socialise and then head back south to Antarctic waters to feed Photo: BARCROFT MEDIA

Courting humpback whales have been captured on film moments before mating.

The rare footage was captured by Tony Wu, an underwater photographer, off the islands of Vava'u in the Kingdom of Tonga.

Swimming close to a pod of southern hemisphere humpbacks, Mr Wu witnessed the "heat run", in which one female is pursued by a number of males until she selects a partner.

Mr Wu captured the rare sight of an aroused male humpback whale swimming gracefully next to the female.

"There is no documented case of anyone seeing humpback whales mate," said the 40-year-old photographer

"I know the whales come here each winter in part to find mates, so there's always a hope of catching something like this.

Mr Wu described the mating ritual.

"The female and males swim, and the males challenge one another, show off to the female, until the female selects a male.

"The process can take a long time, many hours or even days, and has the potential to get rough and violent among the males.

"Once the female has chosen a mate, they spend time together.

"I have spent time with many mating pairs over the years. Typically, they are relaxed, often inquisitive and clearly demonstrate amorous intent to one another.

"They often make body contact, swim in graceful, elaborate, almost choreographed motions," he said.

Each year southern hemisphere humpback whales visit the area to mate, give birth, raise young, socialise and then head back south to Antarctic waters to feed.

Spending six to eight weeks of each year (August-September) with humpbacks in this area, Mr Wu uses his years of expertise to witness such events.