How has global warming affected humpback whales?

After industrial whaling declined with international bans on the practice, the number of humpback whales has risen 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 boundaries. But large, ancient mammals like humpback whales are unlikely to adapt over time. The response of many marine mammals should be to move to cooler regions, at the poles.

Change the course of the humpback

Humpback whales make one of the longest migrations among mammals, traveling routes 4,830 kilometers long, from Alaska to Hawaii, where they breed. Once these animals reach the breeding grounds, they need an environment with temperatures between 21 and 28 degrees Celsius, which is ideal for puppies that do not have as much fat as adults.

As global temperature patterns change, scientists worry that whales will have to change their routes, according to a report from the World Environment Organization. BBC News. A 2022 University of Hawaii study showed that greenhouse gas emissions could put many breeding sites outside the temperature tolerance range of humpback whales.

If fossil fuel emissions are not controlled, experts predict that about 67% of humpback breeding sites will have temperatures higher than the animals can handle.

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

Climate change has already changed the paths of humpback whales. For example, researchers off the coast of Massachusetts in the United States observed that peak occupancy of humpback whales was two weeks later than it was 20 years ago.

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Food and diseases

Humpback feeding areas are also at risk due to climate change. They feed on krill, which are small shrimp-like crustaceans. Before they begin their migration, whales consume tons of these animals every day. But as temperatures rise, the krill population has declined by about 80% since the 1970s.

As a result, humpback whales chase other foods and can become tangled in fishing nets in search of food captured by humans. It also increases the risk of collisions between whales and boats.

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