Narrator: Eugene Linden, who has been writing about animal intelligence for a quarter century, is convinced that it's time to recognize that the divide between human and animal is smaller than we think.

Eugene Linden: They've deceived each other in the wild. They've deceived keepers. They use tools. They create tools. The studies of language have shown that not just apes, but dolphins can understand the meaning of words and of complex sentences, and understand complex ideas.

Narrator: Linden offers his evidence in his latest book, The Parrot's Lament. He turned not to hard-nosed academics, but to people who have devoted their lives to animals— researchers and zookeepers.

Chris Wilgenkamp: Want to bring it down on this side, where it's drier?

Narrator: People like Chris Wilgenkamp of the Bronx Zoo in New York.

Chris Wilgenkamp: Get her to go back and forth to head targets first.

Eugene Linden: On this day, Wilgenkamp coaches a colleague on how to teach an elephant to get its feet ready for inspection.

Chris Wilgenkamp: Let's check her foot out. They know and they remember exactly, when we're doing which set of nails, what position they need to be set in. And each time they take a break, you'll see them alter their position and reset to make it easier for you to get to that nail. To me, that's a direct form of intelligence. They understand exactly what's happening there.

Narrator: Exactly what is happening here? For the trainers, the elephants are doing more than just playing for treats. But are they actually thinking the way we humans do?

Chris Wilgenkamp: You know what they say, brain mass is everything, so with their brain being eight times the size of ours, it's hard to think that they don't have at least our capabilities.

Narrator: There's communication, says Wilgenkamp.

Chris Wilgenkamp: I get them excited by saying good morning, good morning to them. And they get all excited because of that, and their ears start to flap, and they drop their heads down and they start to rumble.

Narrator: They start to rumble. What do you mean, they start to rumble?

Chris Wilgenkamp: A low roar. And you can see the dome in the front of their head, which is an nasal cavity, vibrate— fill with air and vibrate. And you know that at that point they're communicating with you. Although you can't hear it, you can feel it and you can see it.

Narrator: And even elephants half a mile away on the other side of the zoo can hear that rumble.

Alexandra Morton: There's one call in particular.

Narrator: Alexandra Morton is intrigued by equally massive mammals— killer whales.

Alexandra Morton: It sounds like this, it goes— "pa-kair"— like that. And it is associated not so much with one activity, but with the act of synchrony. Any time two or more whales are doing something right together, this family of whales uses this call.

Narrator: Morton has spent a lifetime studying whale communication. She believes that whales not only have language, but dialects that differ from family to family.

Alexandra Morton: In watching them, you'll see them spread out like this, and they talk to each other. And I think a lot of their sounds, they go— "wee-ooo"— I think he's saying, I'm over here and I'm doing well. And, "woo," I'm over here, and I'm doing well. Somebody gets a fish— suddenly, the calls spike. And it's a different type of call, and they all come roaring over.

Narrator: Morton is writing A Passage of Whales about her life among the whales of British Columbia. In her office on shore, or sometimes out at sea, Morton uses what's called a hydrophone to record whale noises and note what sounds go with which whale action.

Alexandra Morton: Over my hydrophone— I had headsets on— comes this big "mroom, mroom, mroom" of a cruise line propeller.

Narrator: Morton claims that on one outing, a family of whales saved her life when she became trapped in dense fog.

Alexandra Morton: I'm starting to panic, because I think at any moment this fog is going to be split by this bow that is ten stories high. And suddenly, "fwoo!" Up pops one of the whales that I'm working with. And I just got this wave of, I'll stay with the whales. I'll be safe with the whales. They stayed right beside me. And then, I could just see a little shape up ahead and, oh my gosh, it's an island!

Narrator: That incident, says Morton, seems to show that the whales had a clear understanding of her predicament.

Alexandra Morton: Certainly their response towards me was not a random move. There's no way that was coincidence. And I can only believe it was a form of empathy. All of this is very intangible to measure, but I do believe it's there.

Narrator: Some animals are capable of pulling off complex mental stunts. For example, no zoo animal is a better escape artist than an orangutan.

Helen Shuman: Towan, can you give me your arm?

Narrator: Helen Shuman of Seattle's Woodland Park Zoo has discovered that orangutans will put up with nasty needles, mindful that it's good medicine. And that's just the beginning.

Helen Shuman: They watch very carefully everything that's going on, and so if you make a mistake, they know it. But they're smart enough to not necessarily to do something right when you're watching them. They'll wait till you leave to do it. So they're a little cunning, too. And I think that's what makes them good escape artists.

Narrator: Towan, here, has had his share of breakouts. But no orangutan is more legendary than the now-deceased Fu Manchu, an honorary member of the American Association of Locksmiths. He once hid some wire in his mouth until it was just the right time to pick the lock on the door to his enclosure.

Man: It required some ability to reverse engineer the locking mechanism, understand that he could use the wire to trip to lock, and that sort of thing— tool use, tool making, all these abilities.

Narrator: All sorts of mental abilities, all manner of thought in all kinds of animals.