When whales breach it’s a spectacular sight, but no one was quite sure why they did it — until now.

Researchers studying humpback whales in Queensland, Australia have discovered that whales breach to communicate with other pods of whales, up to 2.5 miles (4 km) away. The journal Marine Mammal Science published their findings in November 2016.

Researchers studied the whales’ surface behaviors as part of the Behavioral Response of Australian Humpback Whales to Seismic Surveys (BRAHSS) project at Peregian Beach, Queensland. The researchers wanted to know why humpback whales breach and perform other surface behaviors when they migrate. Whales usually fast during their migration, living off body fat. Behaviors such as breaching use a lot of energy, which the animals cannot afford to spare without good reason.

What did the researchers find? 

Researchers observed 94 groups of whales during their migration past the Australian coast to Antarctica during September and October of 2010 and 2011. Staff recorded the occurrence of surface behaviors like fin-slapping the water and breaching to discover what they might mean. They combined their observations with acoustic monitoring and data on the social and environmental context of each whale group before drawing their conclusions.

After study, they found that surface behaviors were more common on windy days and when other groups of whales were far away. The behaviors apparently serve multiple purposes for migrating whales, who use breaching to communicate with far-apart groups and fin-slapping for whales nearer by. The whales also used fin slapping when groups of whales came together or separated.

Researchers concluded the noise from fin slaps and breaching travels long distances. Whales may rely on these techniques to communicate when vocalizations would be lost due to boat and weather noise. While the scientists only studied migrating whales, their behaviors may have the same purpose wherever, and whenever, they occur. Humpback whales fin slap and breach throughout the year and around the world.

Only males produce whale songs during their sexual display. These complex songs can be audible over distances of 6 miles (10 km). The whales’ social sounds, however, such as from fin slaps and breaches, lack the pattern of song. Both males and females produce these sounds in various contexts. Humpback whales migrate around 16,000 miles (25,000 km) each year, feeding in polar waters and breeding in warmer waters. Entanglement in fishing gear, collision with ships and noise pollution all threaten their survival.

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