By Jessica Knoth

“Lab mouse outcompetes his siblings for food because he’s selfish,” would never be the title of a scientific study. In the biology world, scientists are careful not to anthropomorphize their subjects, believing that doing so would compromise the accuracy of the study. However, it seems naive to assume that humans are the only animals that feel emotions or are motivated by instincts other than eating and reproducing. What about elephants who mourn their dead? Or killer whales that help their disabled family members survive?

As a trained biologist, it feels wrong to describe these as examples of “emotion,” but there are instances of emotional response happening in nature, mostly in higher-order mammals with complex familial hierarchies. One of the most well-known cases is that of humpback whales appearing to rescue the prey of mammal-eating killer whales, apex predators who have earned themselves the nickname “wolves of the sea”  because of their organized hunting strategies.

Humpback calves are preyed upon by killer whales when migrating from their southern breeding grounds to their northern feeding areas, prompting humpback mothers to take longer inshore routes to avoid encountering them (Pitman et al. 2016). In the event of an attack, the mother humpback will try to fight off the killer whales, or will place her calf on her belly and lift it out of the water so the predators can’t get to it. What’s intriguing is that humpbacks have been seen demonstrating the same behavior with seals as they do with their calves – lifting them out of the water until the killer whales eventually disperse. The image below shows an interaction in Antarctica where a very lucky weddell seal took refuge on a male humpback’s belly. The humpback was even seen holding onto the seal with his fins when it started to slip off.

In the last 62 years, there have been 115 interactions recorded between humpbacks and hunting killer whales (Pitman et al. 2016), with the majority of these interactions initiated by humpbacks. The larger whales have been observed trying to protect seals, whale calves, and even sunfish from hungry killer whales. The longest known interaction to date happened in Monterey Bay, California in 2012. Described in a National Geographic article, a pair of humpback whales were on the scene when killer whales attacked a mother grey whale and her calf. After the struggle, the calf was killed. Instead of the humpbacks dispersing, however, 14 more arrived and prevented the killer whales from eating the calf. One humpback positioned itself near the carcass, and loudly bellowed and slashed at any killer whales who came near. The humpbacks did this for six and half hours, preventing the killer whales from feeding by slashing at them with their tails and fins. Why the humpbacks protected a different species is a mystery, but scientists speculate that they were trying to prevent the killer whales from eating (Pitman et al. 2016).

Interestingly, not all humpbacks display this “mobbing” behavior (charging while bellowing and slashing with their fins). It is mostly those with teeth rake scars, suggesting they have already had an encounter with killer whales and survived (Pitman et al. 2016). So what is their motivation for this behavior? Is it simply because of a dislike of killer whales?

The three most likely theories are kinship motivation, interspecies altruism, and empathy. The most scientifically logical explanation is that of kinship motivation, or the desire to protect other animals related to them. Humpbacks return to the same breeding sites every year, so it is possible that a whale being attacked in the area shares their genetics. The issue with this argument is that the humpbacks fight for other species, not just their own. So why do they protect other whales or seals and risk injury instead of retreating? Perhaps fighting the killer whales brings in a degree of intimidation so that they will be less likely to attack humpback whales in the future. They may also decide to help out since they have already expended the energy getting to the scene without knowing what is being attacked. This could explain why humpbacks have also been observed behaving aggressively towards false killer whales or short-finned pilot whales (Pitman et al. 2016), both of which are known to prey on mammals.

This introduces the idea of interspecies altruism – helping another species with no discernible benefit. Very few species have been observed doing this, and most have been dolphins. They’ve been observed assisting humans and other dolphin species in distress. An interview by National Geographic of the president of the Whale Sanctuary Project, Lori Marino, quotes her saying “[h]umpbacks are capable of sophisticated thinking, decision-making, problem-solving, and communication. So, taken altogether, these attributes are those of a species with a highly developed degree of general intelligence capable of empathic responses.” In other words, we shouldn’t be surprised that a highly intelligent cetacean can feel empathy towards a seal scrambling for its life.

In short, scientists don’t know why humpback whales have made themselves vigilantes of the sea, but it is certainly possible that they are motivated by a variety of factors, including a dislike of killer whales or empathy for their prey. Similar behaviors have been seen elsewhere in the animal kingdom, and it is a fascinating area of research. They may not wear a cape, but to seals and other prey animals, humpbacks are saving the day.