Hacker News Reader

Comment by dalbasal | Hacker News Reader

Whether or not something is a predator is a lot more important to us than to biology. The distinction between eating small krill and eating large fish, even less so.

Lots of mammals seem to evolve back and forward between various food sources. Look at our branch. Most/many primates have a mixed diet, in many of the families. There are some specialists like gorillas and bleeding heart baboons, and they’re not necessarily related.

So, our ancestors were probably all over the predator-prey spectrum.

View on HN

Not to mention, krill are animals. Only at the scale of a whale could filter feeding be considered gentle giant behaviour. At our scale it's probably more like genocidal giant if you consider the thousands of little animals which dissolve alive inside the whale.

It's not so much what whales eat that matters, rather than how they eat it. The size difference between a whale and a krill is so big that for all intents and purposes, whales feed much more like a cow than a lion. They're browsing, except they don't browse vegetals, but small animals.

To say they are not predators makes sense in the behavioral sense.

They do actually hunt for denser populations of krill. So, IMO it's closer to predator behavior than pure browsing.

Cows also seek out denser grass, so that hardly destroys the analogy.

Another angle to look at it might be how much the prey try to avoid being eaten. I know nothing about Krill, but if they have any navigation control and/or instincts, I imagine that differs greatly from cows.

Granted, I've never observed grass to see if it avoids cows either. /shrug

Many plants do have defensive measures to ward off herbivores. For example, when grass is damaged it releases numerous chemical signals into the air. This is what causes the freshly-mown lawn smell: http://mentalfloss.com/article/30573/what-causes-fresh-cut-g...

These defensive measures have a huge range. Some might only increase healing, others might attract life higher up in the food chain to attack the herbivores, and still others might be able to actively damage the herbivore.

My point is that eating plants may be less passive than we think. All of life has had billions of years to evolve, so the interactions can be pretty sophisticated all around.

Bubble netting is a little more complex than just walking to a new area. https://en.wikipedia.org/wiki/Bubble_net_feeding

Also, baleen whales are not limited to krill and do eat a lot of larger fish.

They are not browsing, they actively hunt game, corral them, and eat them. They are quite literally predators in the behavioral sense.

This is illustrated nicely on the BBC series "The Hunt". Not only to they corral but they work with other fish in this process. There's a great scene where a Blur Whale comes out of the corner opening it's mouth and just swallows a massive gathering of krill. Highly recommended!

Reply on news.ycombinator.com