Humpback whales in Alaska: migration, population history and effect of tourism

Last summer, I had the privilege of going on a cruise through southeastern Alaska and the Pacific Northwest of the USA. A highlight of my trip was watching humpback whales off the coast of the Alaskan capital city, Juneau. Being the zoology writer I am, I wanted to know what brought humpback whales to Alaska, and whether human activity like my tourism affects their behaviour. This article describes exactly that – mixing fun facts about humpback whales with a serious reflection on how human activity has affected them.

About humpback whales

At about 15 metres long, humpback whales (Megaptera novaeangliae) are much bigger than I pictured when we booked the whale-watching trip. They are best known for their acrobatic dives where they lift their tails in the air (Figure 1). Since individuals can be identified from their tail patterns, the behaviour and migration of humpback whales are easy to study. Humpbacks eat krill and small fish like herring, sand lance, and capelin. Instead of teeth, they have “baleen”, which are a filter system in the mouth made of keratin. We were shown a baleen filter plate on the whale-watching boat in Juneau and, like the whales themselves, the size astounded me. 

Migration

Humpback whales travel over 5,000 miles twice a year, one of the longest annual migrations among mammals. They move between cooler water for feeding in the summer and warmer water for breeding in the winter. For Northern hemisphere whales, this means travelling north for their summer feeding and south for their winter breeding (Figure 2), though humpbacks are found in all oceans worldwide. Since I saw the whales in Alaska in June, I was at their feeding ground – and our tour guide pointed out characteristic feeding behaviours as we saw them. This feeding is crucial for humpback whales to accumulate large energy stores, since they do not eat during the months of migration or breeding. Satellite tracking shows that humpback whales migrate in a remarkably straight line. While birds use the Sun or the Earth’s magnetic field to stay on course, and humans nowadays have GPS tracking, scientists do not yet know what cues humpback whales use to swim in a straight line for such long distances. 

Population history in the North Pacific Ocean

Unfortunately, humpback whales were victims of commercial hunting in the 20th century, as former sources of oil and keratin. One study estimated that over 25,000 humpbacks were killed in the North Pacific Ocean (including Alaska) between 1900 and 1999. As countries realised commercial whaling was unsustainable, the industry was increasingly regulated, culminating in a commercial whaling ban in 1966 and more restrictions in 1982. Through the 1990s and 2000s, humpback whale populations recovered such that the North Pacific Ocean population reached a peak of 33,488 in 2012. However, the 2010s and 2020s have brought new challenges to North Pacific humpback whales. There was a devastating Pacific Marine Heatwave in 2014-16 which, combined with global warming, may have stressed Pacific humpback whale populations. As mentioned earlier, cooler water is preferred for feeding and warm water for breeding, so warmer oceans could disrupt humpback behaviour, migration, and survival. Other modern threats include ship collisions and entanglement in the nets of commercial fishing boats. Consequently, the North Pacific humpback whale population has declined to around 26,000 whales as of 2021.

Effect of tourism on Alaska’s humpback whales

With human activity like whaling and global warming threatening humpback whales, I wondered what role tourism played. Amrein et al found that when whale-watching boats were around, humpback whales adjusted their communication gestures, like jumping out of the water or tail-slapping. This might be because the noise pollution or physical obstruction from boats interfered with whale communication. There is lots of evidence that whale-watching boats affect the swimming speed and direction of humpback whales, as if they were avoiding predators. If boat avoidance takes energy away from essential processes like feeding or nursing, this could threaten humpback whale survival. Nursing interference is especially an issue since mother-calf pairs prefer to swim closer to shore, where the tour boats also are. According to Schuler et al, humpback whales spend more time feeding, and less time travelling and doing their surface gestures, in the presence of whale-watching boats. All these changes in energy expenditure could accumulate into long-term stress. Fortunately, there are responsible whale-watching guidelines in place to minimise these negative effects of tourism on humpback whales. My tour operator in Alaska, alongside many others in the US, is signed up to the WhaleSENSE program (Figure 3), in which tour boats agree not to disturb the whales during their operations. For example, we observed humpbacks from at least 100 yards away at all times.

Responsible whale-watching can benefit local communities as well as the humpbacks. The whale-watching industry in Juneau was worth $32 million in 2006, so it must contribute even more to the Alaskan economy today. Speaking to the tour operators at different stops of my cruise, I learned that thousands of livelihoods rely on the tourism industry in the coastal Alaskan towns we stopped at. From the humpback whale’s perspective, tourism is a better way of making money off their feeding grounds than whaling. WhaleSENSE operators also raise awareness about humpback whale conservation initiatives during their whale-watching tours, and tourism revenue is often invested in conservation. By inspiring me to write this article and raise awareness about the devastation of commercial fishing and climate change, I hope my tourism was a net benefit for the whales.

Conclusion

Humpback whales are majestic creatures with their patterned tails and grand communication gestures. They feast on zooplankton and fish in places like Alaska, before migrating thousands of miles without any food to breed in warmer waters. However, climate change, commercial fishing/whaling, and even tourism can interfere with humpbacks at every stage of their life cycle. Therefore, my short time on that whale-watching boat in Alaska has inspired me to be a lifetime steward not just for humpback whales, but all marine life.

Written by Simran Patel

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