Tough Love: Aggressive Encounters Between Humpback Whales

As the countdown to Valentine’s Day begins you may sense that love is in the air, but for one of the ocean’s largest swooners, the season of love has already been in full-swing.

February through March is peak season for the estimated 10,000 humpback whales that migrate through the Hawaiian Islands to mate and give birth to their young. While a number of female whales have already arrived with calves (yearlings) or are late in their pregnancies, many are in the midst of finding a mate.

The 40-ton male humpback is a master of showmanship, putting on grand displays of surface breaches, singing songs that can travel up to 20 miles, escorting females, or fighting off rivals. While it’s commonly assumed that the purpose of the male’s song is to attract a female, there’s actually very little evidence that proves this claim. In most cases, a male singing is often met by another male. This complex behavior has been studied extensively, however many still do not fully understand its function other than that it coincides with mating season.

Humpback-breach
Humpback breaches are one of the most exciting behaviors to observe. Its purpose remains a mystery, but researchers believe it may be a form of communication, play, or ridding parasites.

Singing is synonymous with warm feelings evoked by love and affection, but competition for a female humpback can be quite fierce, often sparking brawls among these ocean giants. Aggressive behaviors are common in competition pods, a group of humpbacks characterized by a single female (sometimes with a calf) in the center of multiple males. The male closest to the female is the primary lead or escort whale as it has the best chance at mating with the female. The escort defends its position from challenging males, resulting in flurries of aggressive behavior in an attempt to supplant the escort whale.

Male humpbacks use a number of tactics to threaten rivals. Underwater, he may hunch his back, deploy bubble streams, or vocalizes booming sounds ranging from screeches to low growls. At the surface, he will raise his head and slap the water, inflate his ventral pleats to appear larger in size, clap his jaw, or slap his tail.

When threats aren’t enough to ward off challengers, competition can escalate to physical contact. Using their massive size, males will often induce physical strikes including head lunges, raking (rubbing barnacles against a rival whale), peduncle throws, and other collisions. “It’s an underwater football game with 40-ton players,” states Maui Ocean Center Aquarist Jen Kogan, “It’s a period of constant collision and physical contact to become the primary escort male, a position that can change at any minute.”

Humpback Whale Penduncle Throw
Peduncle throws are one of many aggressive behaviors used by a male humpback in a competition pod. Raising its tail above the surface, the whale slaps its peduncle ( the muscular body part that connects to the tail) against the water, sending a resounding “crack” to ward off approaching males.

The escort whale follows the female as if he were her shadow: if she travels, he travels, if she pauses, he pauses. He will even mimic her breathing and diving patterns. It is believed that the escort whale shows high levels of aggression not to defend the female from harm, but to maintain his chance to mate once she comes into estrus and is receptive to mating. However, this is one of several theories as to why males escort females, as the exact reasons are not fully understood.

The nature and meaning behind Hawaii’s humpback whale behaviors continues to lure and enthrall. Their exact origin, the truth behind their intellectual and social interactions, and why they sing eludes precise definition. But the unknown adds to the wonder of these magnificent giants. As we enter peak season for whale watching and competition pods are active, we can be assured of awesome displays of power, strength, and beauty.

Written by Evan Pascual, Marketing & Public Relations Coordinator. “Ka Mo‘olelo Moana,” or “The Ocean Story,” is a monthly column written by Maui Ocean Center and published in The Maui News. For a limited time, Maui Ocean Center offers whale watch tours with Aloha Blue Charters. Click here to learn more.

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