Humpback whales spend the Southern Hemisphere winter in Tonga's warm waters for two reasons: to give birth and raise calves, and to mate. Most of the behaviors you'll witness during a trip to Tonga are connected to one of these two purposes.

Mother and Calf Pairs

The most common encounter in Tonga is a mother with a young calf. Calves are born during winter months and grow rapidly on the mother's fat-rich milk. In the early weeks, calves are close to the surface and relatively inactive, resting while the mother hovers below or nearby. As weeks pass, calves become more energetic and curious, breaching repeatedly, swimming in tight circles around their mothers, and sometimes approaching boats or swimmers on their own.

Mothers are protective and will position themselves between perceived threats and their calf. A mother that is swimming slowly, staying close to the calf, and not reacting to the boat with evasive movement is calm and comfortable. A mother that keeps diving and resurfacing, or that positions her body between the swimmers and the calf, is communicating discomfort. Good guides read these signals and keep their distance.

Escorts and Heat Runs

During peak season in August, you'll often see a mother and calf accompanied by one or more male whales. These escorts compete for proximity to the female. When competition escalates, it becomes a heat run: multiple males charging through the water at high speed, breaching, striking each other with tails and fins, and jostling for position. Heat runs cover significant distances and can involve 5-15 males at a time. You don't enter the water during heat runs. You watch from the boat, and it's spectacular.

Breaching

Breaching is one of the most dramatic whale behaviors and also one of the least fully understood. A humpback launches most of its body clear of the water and lands with a crash that can be heard from kilometers away. Theories include communication, parasite removal, play, or a display of strength. It happens throughout the season, from calves practicing small leaps to adults launching full bodies. It never stops being surprising.

Singing

Male humpback whales sing complex, evolving songs during the breeding season. These songs, unique to each ocean population, can last for hours and carry for tens of kilometers underwater. You can sometimes hear humpback song clearly while snorkeling, without any amplification. The sound is otherworldly, and if you surface and notice you've been underwater longer than intended, this is probably why.

Resting

Whales sleep in a state called logging, floating motionless or near-motionless at or near the surface. A resting whale looks deceptively passive, but experienced guides don't put swimmers in the water with them. A whale that surfaces from a rest dive unexpectedly can create a significant wake. Resting encounters are observed from the boat.