Being one of the largest animals in the world, it’s no surprise that humpback whales have an appetite to match! Capable of consuming over 5,000lbs of food per day, you might be thinking that they’re feeding on heavy prey like seals or sea lions, but this could not be further from the truth.
Humpback whales actually feed exclusively on small prey items – krill, herring, and other bait fish being particular favourites – so instead of targeting fewer, larger meals, they instead will spend all day grazing on as much smaller food as they can find. Their throat is only the size of a grapefruit, so even if they wanted to give it a try, any larger food wouldn’t fit! It’s actually this approach that has been credited as explaining just how big these whales, and other baleen whales, can be; by feeding on smaller food, they don’t have to exert much (if any) energy while hunting, so get to maximise the amount of calories they gain.
With such large animals hunting such small prey, and needing to consume so much of it every day, it’s understandable that these whales have to put more than a bit of thought into how they hunt. Through the evolution of multiple different feeding strategies, humpback whales are able to take full advantage of the meal in front of them, adapting their approach depending on what they’re eating, the prey’s behavior, and even who else is around. While we’re sure there is still more to discover, take a look below for just some of the feeding tactics these gargantuan gobblers employ…
The Mechanics behind the Mouthful
If you are ever lucky enough to see the underside of a humpback whale, or indeed if you look closely at a photograph, you will see that the underside of their head through to the start of their belly is covered in pleated folds of skin. This is one of two crucial adaptations when it comes to humpback feeding. The other is their baleen. Found hanging from the roof of their mouth instead of teeth, baleen is a fibrous substance made of keratin that looks and feels similar to very thick hair, but is capable of straining water.
As the humpback whale opens its mouth to engulf food, it will inevitably take in water at the same time. The pleated skin acts like an accordion during the feeding process, opening up to allow the mouth to swell like a balloon, accommodating all of that water (and food). Once the humpback has its mouth full, it will close it again to trap the food inside, then using its powerful tongue will force all of that water back out between its lips. On the way, that water will be strained through the whale’s baleen, which acts like a sieve to ensure the tasty food within it stays in their mouth. The humpback whale is left with a meal, and promptly swallows it down that tiny grapefruit-sized throat!
Feeding in the water column on swarming prey like krill is easy with this basic approach, known as ‘deep dive feeding’. The whales will simply swim through their target, opening their mouths as they do so, and with minimal effort are able to take in huge mouthfuls of nutritious food. This works well enough, but for different prey or prey behaviour, they have to get creative!
Take the Lunge
September in the waters around Vancouver Island is a great time and place to be a humpback whale, and a great time and place to witness ‘lunge feeding’. After months of growing, young herring start to leave their nurseries in the rocks and venture into the open ocean. Here, they are often rounded into bait balls by the local seabirds – shimmering, tight shoals of fish that form as a defence tactic against predators.
For the fish, these bait balls offer excellent safety against seabirds that attack from above, providing a strength in numbers that minimises each fish’s personal chances of being predated. Humpback whales, however, make light work of them, performing a behaviour we know as lunge feeding.
Diving down under the water, the humpback whales will swim below the bait balls, before rushing upwards towards them. At the last moment they will open their mouths as wide as they can, taking in the whole bait ball in one swift motion. As bait balls exist just below the water, this can make for some phenomenal watching as the whales break the surface with their mouths engorged!
Teamwork makes the Dream Work
Lunge feeding alone works perfectly for small bait balls, but for larger ones, the humpbacks have to take it a step further. Working in a team, the whales will form their own bait ball. The process begins like lunge feeding: they dive down below the fish. From here, the whales will start to blow air from their blowholes as they swim in a spiral shape around the fish, stunning and trapping them within the wall of bubbles. As they swim around, they will also be working their way up to the surface, driving the fish up with them. Finally, at the last moment, all of the humpbacks in the group will lunge feed simultaneously, and each of them will get a portion of the spoils.
While it’s a very rare tactic to witness in the waters around Victoria, so-called ‘bubble-net feeding’ has been seen here in the past, and may well be again in the future. Keep your eyes peeled when you’re out on the water – if you see what looks like a big ring of bubble starting, you may be in luck!
Swish and Flick
It can be hard to believe that an animal the size of our boat can be agile, but ‘flick feeding’ is the perfect demonstration of this. By flicking their tails, humpbacks can corral their prey into the perfect spot, or disorientate and stun it into submission – both advantages for easily gathering it in their mouths.
In order to get this feeding strategy right, humpbacks have to hold their heads under the water while they flick. This is of course no issue for an animal that is capable of holding their breaths for 45 minutes, but swimming in one spot with your tail in the sky can’t be easy!
It’s a Trap!
A relatively newly described feeding tactic for humpback whales, ‘trap feeding’ is perhaps the most ingenious of them all. Staying still in the water, with their tail downwards to the depths, the whales will float at the surface with their mouths open wide. This tricks the fish into thinking there is a surface beneath them, and they move into what they perceive to be a shallow pool. Once several fish have been lured, the humpback will quickly close its mouth, trapping all of the unsuspecting fish inside!
By minimizing effort in this way, the humpbacks get to enjoy every single fish to the fullest, knowing that each one is helping it to regain all of the weight it needs in order to survive its migration. As these whales leave the waters off Vancouver Island and head south towards Mexico or Hawaii, they may well be taking in their last meal for seven or eight months, so it’s vital that they pack on the pounds while they can. Trap feeding, as well as deep dive feeding, lunge feeding, bubble net feeding, and flick feeding, all show just how versatile and adaptable these intelligent animals are, and we look forward to welcoming them back every season to watch the banquet unfold all over again.