How has global warming affected humpback whales?

2024-10-26 22:20:00

After the reduction of industrialized whaling with the international ban on this practice, the number of humpback whales has increased again. However, the giant mammals face a new threat: global warming.

Some marine species are able to adapt to changes in temperature and remain within their current geographic limits. But large ancient mammals like humpback whales are unlikely to adapt in time. The reaction of many marine mammals must be to move towards colder regions, towards the poles.

Changing the path of humpback whales

Humpback whales make one of the longest migrations among mammals, covering routes of 4,830 km, from Alaska to Hawaii, where they breed. Once in the breeding grounds, these animals require environments with temperatures between 21 ºC and 28 ºC, ideal for cubs who do not have as much fat as adults.

As global temperature patterns change, scientists fear whales will be forced to change course, according to a report BBC News. A 2022 study from the University of Hawaii shows that greenhouse gas emissions may place several breeding sites outside the temperature tolerance of humpback whales.

Image: Craig Lambert Photography/Shutterstock

If fossil fuel emissions are left unchecked, experts predict that about 67 percent of humpback whale breeding sites will have temperatures above the animals’ tolerance.

For the authors of the study it is important to establish protected areas that take into account future changes in the whales’ breeding sites. Some humpback whales could discover new breeding areas further north on the planet, provided they have suitable seabed and protection from predators. However, protected areas for each humpback whale population must be defined on a case-by-case basis.

Climate change has already changed the routes of humpback whales. Off the coast of Massachusetts, US, for example, researchers noticed that peak humpback whale occupancy was two weeks behind what it was 20 years ago.

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Credit: OSTILL is Franck Camhi – Shutterstock

Food and disease

Humpback whale feeding grounds are also at risk due to climate change. They feed on krill, a small crustacean that resembles a shrimp. Before starting their migration, whales consume tons of these animals per day. But as temperatures have risen, the krill population has declined by about 80 percent since the 1970s.

As a result, humpback whales pursue other food and may become entangled in fishing nets in search of food caught by humans. It also increases the risk of collisions between whales and boats.

Furthermore, climate change increases the risk of disease among whales. Scientists have observed evidence that these large mammals appear thinner and covered in parasites.