|This is not what I look at all day (photo from FIRMM.org).|
Finding dolphins, especially in Hawaii, can be really time consuming and difficult. Especially if you are interested in the types of dolphins that don't generally hang out near shore, which is most Hawaiian species (the exception being spinner dolphins).
Searching for dolphins at sea requires something called a "search image." Visual predators use search image all the time to find food. For example, blue jays look for the color, shape, or pattern of a moth to find their food. Prey can also use a search image to look out for predators: sea lions also use a visual search image to watch out for hungry killer whales. If a killer whale doesn't match their search image - for example, by having a weird, bent over dorsal fin - sea lions don't always recognize it as a threat.
Biologists also use search images. Bird biologists look for something moving against a still background. Snail biologists look for a round, white spiral in a sea of shaking green leaves. And dolphin biologists look for moving triangles (dorsal fins) in a sea of other moving triangles (waves).
|Lots and lots of blue-gray triangles. But which is a dolphin?|
Photo by Alexis Rudd, 8/15/12.
So, most of the time, when whale and dolphin observers are looking at the ocean, it's like looking at this (you might want to adjust your screen so you can only see one of these .gif files at a time - it's making me kind of queasy):
When a large whale comes along, the observer sees a shape in the noise that isn't changing for a little while, like this:
Did you find the "whale?" Hint: it's the blacker spot that appears in the bottom right hand corner for about 3 seconds.
Dolphins are even harder to see, because they move faster. When a scientist is searching for a dolphin, they look for a shape that isn't changing very much, but might be moving across the waves. Can you spot my "dolphin?"
That one's kind of hard (I am having trouble, and I made the thing!), so I made the "dolphin" pink. Now can you see it?
This week, I've been out on the water on the big island, helping look for whales and dolphins. We usually get out on the water at about 6:00 am (sometimes a little earlier) and come back in at 3:00 pm (if we're
Isn't the human brain an amazing thing? It can pick up a tiny difference in pattern -
"That bit of the ocean isn't moving as much as the other bits!"
out of an enormous amount of noise. There isn't much on earth that's more enormous than the ocean.