LIANE HANSEN, host:

Now, a love story from a different species. Every year at this time, after months at sea, hundreds of northern elephant seals return to the beaches along the California coast where they were born. It's an amazing spectacle, and the subject of a new documentary, "A Seal's Life."

Drew Wharton produced and directed the documentary. Dr. Burney Le Boeuf is an expert on elephant seals and a scientific adviser for the film. And both of them are joining us from the Ano Nuevo State Reserve in California.

First of all, Drew, I know you're there. Welcome.

Mr. DREW WHARTON (Director and Producer, "A Seal's Life"): Thank you, Liane.

HANSEN: Are the seals there?

Mr. WHARTON: Yeah, we're actually within just the first couple of weeks of many of the seals returning from migration. We're standing in the middle of about a thousand animals right now.

HANSEN: Well, I mean, describe what you see.

Mr. WHARTON: Well, you know, a typical male is three, 4,000 pounds, 15 feet long. Right now, they're - they essentially come ashore and since they've -they've just swam probably 5,000 miles, they're little on the tired side. So everybody is resting. You're going to hear males fighting. The females are kind of resting and laying next to their pups, if they've already given birth, and yeah, there's just a lot of big animals out here on the beach right now.

(Soundbite of laughter)

HANSEN: Would you put Dr. Le Boeuf on the line?

Mr. WHARTON: Absolutely.

Dr. BURNEY LE BOEUF (Research Professor, Biology, University of California Santa Cruz): Hello.

HANSEN: Hi, Dr. Le Boeuf.

Dr. LE BOEUF: How are you?

HANSEN: I'm well. Thank you. What kind of shape are the seals in now? I mean, they've been out for several months.

Dr. LE BOEUF: Oh, they're in great shape. The males have done some bench feeding in the Aleutians for about 40, 50, 60 days. Then they had a long migration back to the rookery here in central California. And of course, the females are in good shape too. They have been feeding for eight months over the course of their pregnancy. So six days after the females arrived, they'd give birth to a single pup, which they nurse for four weeks. At the end of this time, they copulate, go back to sea and feed and start all over again and basically are pregnant most of their adult lives once they start breeding.

HANSEN: Is this almost, in many ways, like a family reunion?

Dr. LE BOEUF: Well, I wouldn't call it that. It's a traditional breeding place. I don't want to call it a bar and make an analogy with humans.

(Soundbite of laughter)

Dr. LE BOEUF: But let me put it this way, there are few places where there's a live sandy beach where females can gather, give birth and raise their pups, and these are scattered along the coast. The males have learned to predict exactly where the females would be and they'd come here for one reason alone, and that is to mate with the females. And now the whole social organization is arranged around securing as many copulations as possible.

HANSEN: It really does sound like a seal's singles bar.

Dr. LE BOEUF: I agree.

(Soundbite of laughter)

Dr. LE BOEUF: And the best fighters are the best lovers, if you will.

HANSEN: Now, you don't dim the lights and play soft music or anything like that, right?

Dr. LE BOEUF: No. An elephant seal don't dance either. They just go straight to it with no fancy now.

(Soundbite of laughter)

HANSEN: They don't even get a dinner out of it. They've already eaten, right?

Dr. LE BOEUF: They don't get a dinner. I guess another question would be: What are the females get out of it? There's an interesting thing that happens. Usually when a female is accosted by a male, she says no. And she says this with a very forceful vocalization.

If, however, the male who's accosting the female is high-ranking, well, she can reject as much as she wants to because the male will continue. At a certain point, she may decide, hey, this is a high-ranking male. If I'm going to have offspring, I want them to be the sons or the daughters of a male who is well placed. I may as well mate with him. And so they may change their minds.

(Soundbite of laughter)

HANSEN: And what a load of noise they're making too, huh?

Dr. LE BOEUF: Yes. And if you want to talk about the noise, I can tell you that. You'll hear three principal sounds, if you can dissect one out from the other. The principal sound is the threat vocalization of males.

(Soundbite of a male elephant seal)

Dr. LE BOEUF: And they're (unintelligible) each other to establish a dominant hierarchy, which gives them access to females. And they recognize each other's voice, which demands a certain level of intelligence, because this - you may have to remember as many as a hundred other males. That's one sound. The second sound is females making a pup attraction call.

(Soundbite of a female elephant seal)

Dr. LE BOEUF: They give a peculiar kind of call, which enables the pup to recognize the mother and the mother recognizes the pup's voice in return. The last call you'll hear quite frequently is what we call a female's rejection call, a female who's being accosted by a male who is saying no, I'm not interested. I don't want to do this.

(Soundbite of a female elephant seal's rejection call)

HANSEN: A noisy lot, this crew.

Dr. LE BOEUF: A noisy lot, indeed.

HANSEN: Would you put Drew back on the phone, please?

Dr. LE BOEUF: Yes. Here he is.

Mr. WHARTON: I'm back.

HANSEN: Elephant seals, if I'm not mistaken, were once on the brink of extinction. Are they…

Mr. WHARTON: Yeah.

HANSEN: …still threatened?

Mr. WHARTON: You know, at a turn of the century, you know, there were, as you said, hunted to the brink of extinction, basically, for their blubber, their oil. And with only a handful of animals alive around 1900, the population continues to rebound with protections that both our government and the Mexican government years ago put in place as well as all the fine work that agencies like the California State Parks System, and all those national marine sanctuary program. I think the numbers today are somewhere around 150,000 animals.

I think Burney would concur that - I think one of a - the remaining concerns would be the lack of genetic diversity. You know, with only less than 50 or a hundred animals, you know, at the turn of the century when they started their rebound, there are some concern as to their adaptability in the years to come and whether there may be some weaknesses genetically with elephant seals.

HANSEN: Let me speak to Dr. Le Boeuf.

Mr. WHARTON: Okay. Sure.

Dr. LE BOEUF: Hello.

HANSEN: Hi. Does the health of the seals that you're observing there now tell you anything about the health of the ocean?

Dr. LE BOEUF: Yes, it does, indeed. We did a study that encompassed about 40 years. Starting about 1970, it had a very warm period in the ocean. Ocean warming is a great concern. Throughout this warm period which lasted until the late 1990s, the mean weight of the pups decreased significantly. And it was aligned with a very strong El Ninos, which is warm water over the ocean. Its fair assumption of mean weight is highly positive and correlated with survival.

And we know why the mean weight went down. When the ocean is warm, such as during a strong El Nino, the females have more difficulty finding food. They have to spend more effort doing this, and they gain less weight. And there's a direct connection between what a females weighs when she arrives and the birth weight of her pup and how much nutrients she has to feed up to weaning over a four-week period. There's a direct connection.

HANSEN: So when do the seals return to the sea?

Dr. LE BOEUF: It depends on the sex and age. The females do all of their business in about 34 days. They give birth, nurse their pups, copulate and then they're gone back to sea. It feeds for two months. They come back to the same (unintelligible). This takes month. And then they spend eight months at sea over the course of pregnancy, then they breed again.

Males are slightly different. Males - a dominant male may be over here fasting throughout the breeding season for three, three and half months then it goes to sea and feeds for about three months, comes back to molt for a month and then goes back to sea again for another five-month period before starting the whole process over it. So, essentially, both sexes are at sea twice a year or on land twice a year.

HANSEN: But sometimes they're not together.

Dr. LE BOEUF: No. They're never together. They're only together during the breeding season. They go to sea singly. Even individual males or acting as individuals, they never go in a group, or the same thing is true for females.

HANSEN: And they only get together again on the beach twice a year.

Dr. LE BOEUF: During the breeding season for the annual party.

HANSEN: Dr. Burney Le Boeuf is associate vice chancellor for research and research professor of biology at the University of California Santa Cruz. Drew Wharton directed the documentary "A Seal's Life," which is available on DVD and will screen in selecting as an education institutions across the country. Both of the men joined us from the Ano Nuevo State Reserve in California, scene of elephant seal breeding season.

Thank you so much and do thank the seals for us, too. If you can get a word in each of us.

Dr. LE BOEUF: Thank you very much.

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