Since November, numerous humpback whales have been spotted near the coastlines of Faxaflói Bay. We have seen between 1-5 on any given day, either close to Reykjavík or Hafnarfjörður. At the time of writing there are 4 just outside the harbour of Hafnarfjörður. This has become increasingly common during the winter in recent years.
Humpback whales are a type of a baleen whale. Baleen whales are well known for spending their time in different locations. Typically, this means they will have a place where they feed and another place where they breed. However, in recent years we are finding more and more are staying in the feeding ground all year round. In this blog, we will explore why humpbacks migrate and what could be causing this shift in their patterns.
Map showing the migration of different humpback whale populations around the world. Those that feed in Iceland migrate to the west coast of Africa or the Caribbean for breeding (~6000km). You can also see the longest migration for a humpback whale is between Antarctica and the west coast of South America (~8000km). This graphic is taken from GRID-Arendal (https://www.grida.no/resources/7650) and is by cartographer Riccardo Pravettoni.
Summer Feeding Grounds
During the summer humpback whale numbers are at their peak in Iceland, there are an estimated 15,000 individuals. These individuals are all here for the food. During summer, Iceland experiences long daylight hours, which benefits phytoplankton, the foundation of the marine food chain, as they photosynthesise. In doing so they take in carbon dioxide from the atmosphere and release oxygen. The cold waters of the north Atlantic also hold a lot of nutrients. All these factors lead to a high amount of productivity. This means other marine species have lots to eat. Abundant food allows smaller marine species to thrive and reproduce, ultimately supporting top predators like humpback whales. They can eat up to 3 tonnes of food in a single day! Therefore, it is very common to see lunge feeding on summer whale watching tours. A special technique of feeding, bubble-net feeding, is also becoming more and more common. This is when an individual or multiple humpback whales blow bubbles in a circle to trap the fish. They will then lunge at the fish with their mouths open to eat as many as possible. Through this link you can see a video of a humpback bubble net feeding in July 2024 on our Instagram page. The video was taken by Alex Pauimer.
These pictures show humpback whales feeding. The picture on the left is an example of lunge feeding where the whale has swam up to the surface with their mouth open to capture as many fish as possible. The picture on the right shows bubble net feeding. You can see the lighter coloured circles on the water. These circles are from bubbles blown by the humpback to trap the fish in the middle where the whale is coming up to feed on them. This was only performed by one whale, in Alaska it is very common to see this behaviour performed by a group of whales. Both photographs were taken by Rob Hyman.
Winter breeding grounds
Humpback whales will then travel up to 8000 km to warmer waters for breeding. These whales will mate one year and return to the same place the next to give birth. The reason they have to keep coming back to a feeding ground is because there is little to no food in the breeding grounds. In terms of going to warmer places to breed, there are a few reasons why. Firstly, being in warmer waters makes the process of giving birth smoother. The calf will go from a warm womb to a warm external environment. The calves have less blubber (fatty tissue) compared to adults and so if they were born in cold places they will be shocked and may even die. Therefore, it is much safer in a warm place. Also in these warmer locations there is reduced risk of predation. Orcas (killer whales) will predate upon humpback whale calves so this reduces that risk and therefore means the humpbacks are safer.
This is the fluke of a humpback whale named Davy Jones II. An individual seen every year from 2021 to 2024. On the right you can see 5 lines called rake marks. These are from an orca, likely from when this individual was much younger. This humpback whale also has a part of the dorsal fin missing, maybe also due to an orca attack. Photograph taken by Megan Whittaker.
Winter feeding grounds?
We are having more and more success every winter now though! Since 2022, the number of humpbacks seen in the winter has been increasing annually. From 2016-2020 we would see humpback whales on 20.2% of winter tours. But after that, the success rate has increased to 67%. At the time of writing, we have seen humpback whales in 96.4% of tours in the winter of 2025.
This graph shows the percentage of tours during the winter where a humpback whale was spotted. Since 2021, there has been a dramatic increase in the number of tours spotting humpback whales.
Here we will look at a few of the reasons behind why we may be seeing an increase in humpback whales during the winter:
An increase in food could be a vital reason. A species of fish called sprat has been found spawning close to the coast in Faxaflói Bay for 5-6 years now. This means there is a larger supply of food for the humpbacks. A reason they could be spawning here is because close to the coast the temperature is slightly lower which means slightly more dissolved oxygen. As the food is close to the coast so are the humpbacks, this means it is much easier for us to find them on whale watching trips!
The population of humpbacks has increased a lot around Iceland, approximately by 10X from the late 1980s to the late 2000s. If the population is increasing it means there will be more juveniles. Juveniles do not migrate as they are not sexually mature. One of our famous winter whales is called Flak. We have seen Flak across 3 separate winters, she has also been seen in the Westfjords during the summer. Perhaps she does her own mini-migrations around Iceland moving a bit further south in the winter. Along with Flak we have seen many juveniles in the last few winters.
Humpbacks will also not migrate if they did not eat enough in the summer. As they move south the food supply reduces so they will end up fasting. If they don’t have a large enough energy reserve through their blubber they won’t migrate. This could be due to a couple of reasons. Overfishing could be reducing the supply of prey for the humpbacks meaning they have to stay. Or, climate change could be moving some of the fish so they have to use up extra energy to feed meaning they can’t feed enough.
Some humpbacks may simply choose not to migrate. The journey is long and reproduction requires immense energy. For example, one individual we have seen a lot of the last 5 years is a female called Neila. Usually she is a whale we see often in the summer rather than winter. It is therefore possible she migrated in the previous years. But, this year we did see her in the winter so maybe she wanted a break.
These two photographs are both of Neila. Neila is one of the humpbacks we can also identify via the dorsal fin, not only the fluke. The white mark you can see is how we can tell it is Neila. The first picture was taken by Miquel Pons on 30th October 2021 and the second was taken by Rob Hyman on 29th September 2024. The first time Neila was spotted was 14th May 2021 and we most recently saw her on 9th January 2025.
Are there any other examples of changes in migration?
Across the globe similar shifts in migration patterns have been observed, suggesting a broader trend. Here are a few examples of this happening:
In Alaska there is evidence to suggest humpback whales may also be skipping migrations to warmer locations for breeding due to a lack of feeding. This could be due to the waters reaching the carrying capacity. This basically means there are too many humpbacks for the resources available.
There is also evidence breeding areas could be moving further south along the south-west coast of Australia. This means the breeding grounds are moving into what would typically be slightly colder waters. If they are now giving birth here it could suggest these waters are warming due to climate change. Other research has suggested the temperature a calf is born in will impact their size as an adult.
Off the coast of Tanzania research is showing feeding behaviours are becoming more common in a breeding ground. This again could be a sign of climate change with fish populations moving.
If these trends continue, we may be witnessing a huge shift in humpback whale behaviour with major ecological impacts. Perhaps other marine species will begin exhibiting similar shifts in migration patterns in the coming years. Of course, if these trends do continue we can at least look forward to potentially seeing humpback whales all-year round!
By Rob Hyman
Comments