Learning to lunge feed

With our blow sampling project ending for the 2018 season, we turned our focus back to whale behaviour in Skjálfandi Bay. Fortunately for us, their behaviour has been spectacular.

Humpback whales belong to the rorqual group of baleen whales, and so they feed by lunging for a shoal of prey (fish or krill) at high speed with their mouth open. With their throat expanding to several times its normal size, they take in a giant mouthful of water and prey, and then force water out with their powerful tongue. In Iceland, their prey usually exists at depth, and so lunge feeding is not normally seen. However, later on in the day, this prey may rise near to the surface: this daily vertical movement of marine life is actually the largest migration on the planet. Should this occur, you may be fortunate enough to watch one of the great wonders of the natural world: surface-feeding whales. When a whale lunges out of the water with its mouth open and full of food, you can get a real appreciation for whale anatomy- the giant mouth, the expanding throat pleats, the baleen and the giant tongue. It is a true privilege to see.

Luckily for us, the last few weeks have provided a lunge feeding event to remember. It started in late June, with perhaps the best whale watching trip we have ever joined in Skjálfandi Bay. In the north-western corner of the bay, we came across a huge gathering of humpbacks- perhaps 15-20 in a fairly small area- and they were all lunge feeding as if their lives depended on it. Rising out of the water with their mouths fully open, some were almost breaching with the enthusiasm of their feeding. Some came up vertically, whereas some tended to feed on their side (usually on their right side). We honestly thought that this couldn’t get any better, until we came across a mother and calf. Not only was the mother lunge feeding like the others, but so was the calf! Well, not quite- they were clearly still learning, surfacing with their mouth wide open and seemingly unsure what to do next. After heading further west, we came across another two mother-calf pairs, who were lunge feeding side by side! Having three calves in the bay is almost unheard of, but to see them learning to feed for themselves was truly exceptional. Hopefully they can continue the learning process!

Luckily, this was not the end of it. The action then moved to the far south-west of the bay, and the lunge feeding continued for several days. At times, we think they were feeding in water as shallow as 5 metres (how a 15 metre whale can do this, we still don’t understand!). Interestingly, they had changed their behaviour slightly, as they were now all lunging on their side, spending more time with their mouth open. Furthermore, the water had an almost milky appearance. We think that fish may have been spawning in the area- we don’t know which species, but it would explain the change in location and behaviour.

Starting at about the same time, we have had another equally incredible series of encounters. For the first time in 6 years, the bay has been visited by northern bottlenose whales (Hyperoodon ampullatus): a beaked whale typically found in deeper offshore waters in the North Atlantic. For the last two weeks, we have had up to three pods in the bay at once, with one pod containing up to 12 animals. This has mirrored other unusual sightings of the species around the north coast of Iceland in recent weeks. Travelling fast and diving for up to one hour, you never know where they will appear next- they don’t seem to have a preference for deeper waters within the bay and we don’t know why they are suddenly visiting this area. Seeing these normally-elusive creatures up close has been amazing, with their long brown bodies and large, bulbous head.

Not to be outdone, the white-beaked dolphins have also turned up in force, with over 100 animals in the bay at times. As we proceed through July, we are entering ‘jumping dolphin’ season and witnessing some incredible aerial displays, from both adults and young calves.

In terms of our research, we are continuing with our behavioural monitoring. We have been out on the whale watching boats almost daily, usually on multiple trips. We have noticed a very interesting trend during the period of frantic lunge feeding. Surface feeding generally occurs in the afternoon/ evening, and the animals don’t appear to be too bothered by the boats (although this is only anecdotal). However, during the morning, the animals appear to spend most of their time resting. In this period, they seem to react far more strongly to whale watching vessels- often diving down as the vessel approaches and only returning to the surface (to continue its resting behaviour) when the vessel leaves the area. However, when we have joined the electric boat with a quiet engine, this reaction somewhat disappeared. We will wait until the season ends to see how significant this may be.

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Lob-tailing humpback (perhaps a sign of aggression towards white-beaked dolphins)

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Breaching humpback!

jumping dolphin!

Jumping white-beaked dolphin. Dolphins can jump in several different ways, and we don’t yet know what information this may convey to other dolphins

2 Comments on “Learning to lunge feed

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