What is looking for dolphins in the ocean really like?

Many people are curious about what it is like to be out on a boat looking for dolphins in Hawaii. Lots of people think it's easy - my job is simply to sit on a boat and watch dolphins. Many people have a hard time believing that you can actually get paid to lounge on a boat and watch dolphins frolic in the surf.  The reality is a lot more complicated.

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.

Looking at waves is a lot like looking at the ants on a tv screen.  It's kind of like watching random noise (although obviously I am oversimplifying things to give you an idea, waves aren't really random).

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 lucky unlucky). For the last two days, we have seen two groups of animals per day. That means that we have effectively been staring at noise for about 8 hours, searching for that tiny little clue that will tell us where the dolphins might be.  Coastal cetaceans are not spread out as much as in the tropics, so there is not always as much time staring at noise.

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.


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What You Know* About the Difference in Dolphins and Porpoises is Wrong**

*Mostly  **Some of the time

Last weekend I was lucky enough to speak at a math workshop for high school teachers put on by some of the University of Hawaii Match Department faculty.  And let me just start out by saying that it was AWESOME.  As anyone who has ever read "How to Win Friends and Influence People" knows, one of the best ways to get people to like you is to ask them questions about themselves.  For scientists, this extends to talking about our research. Beware asking a scientist good, intelligent questions about their work: you may be there for hours!

So, talking to the math teachers was an incredible treat.  They asked great questions, including one of my favorites, "What's the difference between a dolphin and a porpoise?"  Porpoises are from the cetacean family Phocoenidae, while dolphins are in the family Delphinidae.  I love this question, because there are so many misconceptions about what makes a porpoise.  This cartoon does a great job of showcasing those misconceptions:

Let's get the easiest misconception out of the way first: size.  I'll admit the average weight of porpoises is less than the average weight of dolphins.  However, there are many examples in which this just isn't true.  For example:

Dall's Porpoise (up to 200 lbs)

Hector's dolphin (up to 125 lbs)

So size of the animal isn't exactly the best diagnostic to use when deciding whether something is a dolphin or a whale.  How about rostrum (head) shape?

  Risso's Dolphin by Greg Boreham                             Finless Porpoise

Hmm, one of those is a dolphin and one is a porpoise, but they seem to actually have very similarly shaped heads.

OK, FINE! But if it has a bottlenose like Flipper, we DEFINITELY know it's a dolphin, RIGHT?

Northern bottlenose whale  (Hyperoodon ampullatus, in Family Ziphidae)

ARGHHHH!  It must be the fins, then. Dolphins HAVE to have pointy dorsal fins (the one on their back), and porpoises have rounded fins!

Chilean dolphin (rounded)                                                      Dall's Porpoise (pointy)

No dorsal fin at all (Southern Right Whale Dolphin).
The finless porpoise also has no dorsal fin, as the name implies.

OK, I give up, there must be SOMETHING I can use to figure out whether this random cetacean I got in the mail is a dolphin or a porpoise - but what????

TEETH!

Bottlenose dolphin                                |                             Harbor Porpoise

Dolphins have cone-shaped teeth throughout their mouth, while porpoises have what are known as spade-shaped teeth.  Here's a comparison, with A being the porpoise tooth and B being the dolphin tooth.

Dichotomous keys are tools that scientists use to figure out what species they are looking at.  These keys are kind of like those "build your own story" books that you had when you were a kid. You are asked a series of questions, and the questions lead to an ending.  It's also a lot like 20 questions, with each question further narrowing down the possibilities of which species you could have.  In fact, if you were using a dichotomous key to determine the species of a cetacean, the tooth question is what separates the porpoises from everything else.  

Try keying out whale, dolphin, and porpoise species
at the Marine Species Identification Portal!

In general, can you use these rules to distinguish between a dolphin and a porpoise?  Sure you can. But it's important to be aware of the many exceptions. Let's be honest, the likelihood of encountering Dall's Porpoise (found on the US west coast) and Hector's Dolphins (found in New Zealand) on the same day is infinitely small.  Even smaller is the likelihood that they'll give you a good look at their teeth. The best plan is to be knowledgeable about the species you are likely to encounter in your area.

Thanks for the great questions, Math Teachers of Hawaii.  If you'll notice, I haven't actually given much space to the actual workshop.  I'll get to that later. See what happens when you ask a scientist about something that interests them?!

If you ask a scientist a question...
they'll want a cookie.

Who am I kidding, I always want cookies.

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