Whoa, it's been like 2 weeks since I've last updated and now I feel terribly unproductive. I've been super busy working on various projects...honest...
Anyway, to make up for it I thought I'd share this amazing video from the BBC's "Nature's Great Events" series. It describes what is known to marine biologists as a "bait ball." What's a bait ball? Well, you'll probably figure it out pretty quickly after watching the video.
Doing a bit of research on this has left me absolutely amazed by the extent to which nature has adapted predator behavior to take advantage of these tasty little treats. As Wikipedia describes it, "As a response to the defensive capabilities of schooling fish, some predators have developed sophisticated countermeasures. These countermeasures can be spectacularly successful, and can seriously undermine the defensive value of forming bait balls."
Undermining is a huge understatement in this case, because as far as I can tell it means that every fish gets eaten in one fell swoop.
So what's actually going on here? Well, basically there are two kinds of birds working together in order to take advantage of a property of schooling fish. Whenever a school of fish feels threatened enough, it will turn into a "ball" of fish in order to minimize it's vulnerability to the outside world. Unfortunately for the fish, it also compacts them into a tasty little morsel that attracts predators far and wide.
In order to force the fish into a ball, one group of birds begins attacking them from below. They do this by divebombing into the water and swimming up from underneath. This forces the fish upwards, and causes them to go into their defensive ball form. Once they're close enough to the surface, another group of birds begins attacking from the top, picking apart the now defenseless fish.
Or, you could just swallow the whole thing in one gulp.
Birds aren't the only ones who have learned to take advantage of these feeding frenzies, as witnessed by our large friend in the above video. In particular, humpback whales will do what is called "lunge feeding" or, to put it more clearly, opening your giant mouth and forcing everything to fall into it.
Whales salivate (?) at these little balls of fish because it allows them to essentially snatch up an entire school in one fell swoop. Seems like a great way to raise your cholesterol levels...
Anyway, there are apparently too many ways for these fish balls to get eaten than I have room to talk about here (of particular note are swordfish who charge the circle and slash everything in their path, as well as humpback whales that swim in circles under the fish blowing out "bubble nets" to trap the little guys before gobbling them up). Suffice it to say that this is probably not the super clever defensive technique the little fish had in mind.
It's wonderful watching nature carry out it's constant game of cat and mouse. For every defensive technique that one species comes up with, there seems to be a whole host of others ready to take advantage and learn their own workarounds. The next time you're feeling clever, just remember: given enough time, nature will find a way to best you.
As if I need yet another fact laughing in my face for needing glasses since I was in the 3rd grade, a new study coming out of Goethe University suggests that robins can SEE magnetic fields.
It has been widely known for some time now that birds often possess the ability to navigate using the earth's natural magnetic field - this is what allows them to navigate in the same direction over long distances. What hasn't been quite as clear is the manner in which they achieve this amazing feat.
Recent evidence suggests that some birds may simply be doing it the old fashioned way, using a special kind of molecule in their eyes cryptochrome. This molecule becomes activated by blue light coming in through the bird's right eye. It becomes very sensitive to changing magnetic fields, and turns this information into a darkening/lightening of the bird's visual field depending on the strength of the magnetic field (see below).
When researchers blocked the vision of the birds' right eye, they made random choices in the direction they chose, whereas they almost always went north in control experiments. Just one more piece of evidence that our feathery friends are more complicated than we give them credit for!
via Discover Science