They suggest it is an extension of the humpback whales’ “drive” to protect their own calves. Humpbacks may have learned to respond to vocalisations of attacking killer whales, which trigger them to drive the killer whales away, regardless of the species being attacked.

For whales that are toothed, they can use their teeth to attack their prey and protect themselves from certain dangers. However, the two primary tools of defense for whales are 1.) their tail and 2.) When being attacked, whales can thrash their tails around, both injuring and frightening their attacker.

Predators of humpbacks include killer whales, false killer whales, and large sharks; there have been very few documented attacks by these predators on humpback whales, including calves.

Whales are susceptible to collisions with marine vessels, which may cause serious injury or death and can damage vessels. The most lethal or severe injuries are caused by ships travelling 14 knots or faster. …

From 2010 to 2014, 37 whales were reported to have been injured by vessel strikes along the Atlantic coast of the United States and Canada, as well as the Gulf of Mexico. The number of vessel strike-related injuries is estimated as comparable for a number of U.S. West Coast and Alaska species for the same period.

Small vessels not only risk injuring whales, the vessels themselves are at risk of damage.. Small vessels involved in whale strikes have suffered cracked hulls, damage to propellers and rudders, and blown engines. Passengers on board have been knocked off their feet or even thrown in the air and been seriously injured.

Ship strikes are known to be one of the leading causes of death for endangered and vulnerable whale populations, including Critically Endangered North Atlantic Right whales, of which fewer than 500 remain following hundreds of years of hunting.