On a bright summer’s day at the Bronx Zoo, four adult female gorillas nursed their babies until the little gorillas were so full of mother’s milk, they fell asleep in the hot afternoon sun. In the distance, on a hill, a 5-foot-tall, 505-pound male silverback named Ernie gazed out over it all, chewing on a celery stalk.

Ernie is 32 and has been around. Born in the Oklahoma City Zoo, before arriving in the Bronx on May 25, 2010, shipped in a large crate via FedEx overnight express.

When zookeepers describe Ernie, they use words like “cautious,” “gentle,” “patient” and “excellent father.”

Is he also loving? Certainly he knows what he’s doing, having sired four babies who were born to his mates in the last 18 months.

But does Ernie love the five adult female gorillas in his troop? Or is he only in it for the sex?

“I personally wouldn’t use the word ‘love’ to describe the relationship,” said Patrick Thomas, the general curator of the Wildlife Conservation Society, which runs the zoo. When discussing the zoo’s western lowland gorilla troop, Dr. Thomas talks of “procreation” and “propagation.”

On the other hand Carl Safina, during a recent walk around the zoo, spoke of gorilla love. He is an ecologist, a winner of a MacArthur award and author of the recent book “Beyond Words: What Animals Think and Feel.” As far as he’s concerned, gorillas like Ernie and his five female companions feel the same thing in their chest cavities that humans do: the ache of a lovesick heart.

Mr. Safina attributes that special feeling to oxytocin.

“We have the same brain chemicals that create mood and motivation in all vertebrates,” he said. “The only logical conclusion is that their experience is similar.”

Whether it is love or hormones, most visitors to the zoo’s Congo Gorilla Forest do not have a clue how many conference calls, committee meetings, Excel spreadsheets and PowerPoint presentations it takes to produce a healthy relationship between two gorillas.

In the United States, all gorillas are conceived of in Cleveland, or at least that is where the chairwoman of the Gorilla Species Survival Plan of the Association of Zoos and Aquariums is based. The plan involves zookeepers from around the country who meet regularly to oversee the breeding plans for the 353 gorillas currently inhabiting 51 American zoos.

At these meetings, the first step to assembling a new troop is making sure the gorillas will be a good genetic match and thus avoid the sort of inbreeding that helped bring down the Hapsburg Empire.

A gorilla’s personality, sexual experience and behavioral patterns are also factored in.

Because gorillas live in troops, it is not just a matter of a male gorilla’s bonding with a particular female. In Ernie’s case, he has to be able to get along with Julia, Layla, Tuti, Kumi and Suki. And as anyone who has ever been married to even one person knows, trying to stay married to five primates — good luck with that.

Looking for love in New York is not for the meek. “If it’s a young male gorilla that was raised in a very small troop, bringing him to the Bronx, where he’s going to be exposed to four or five adult females, might not be in his best interest,” Dr. Thomas said. “You wouldn’t want to introduce a sexually naïve male that hasn’t had a lot of experience with courtship behavior.” (The human equivalent would be trying to match up an Eagle Scout with Madonna.)

Once members of the species survival committee are confident they have a good genetic and behavioral match, they will give the go-ahead for transferring the gorilla to a new zoo.

About a year ago, officials at the Bronx Zoo assembled a second troop consisting of a male silverback and four females. But, according to Dr. Thomas, the male’s relationship with the others is still shaky, so the troop has yet to appear in public. “It’s easier on him if we can do it in a quieter, off-exhibit area,” Dr. Thomas said. “We can keep an eye on how things are progressing.”

To avoid overpopulation, Bronx zookeepers must wait for a sign from Cleveland to let the baby-making begin. Until then, the females are given a reversible oral contraceptive.

Mr. Safina, who is a professor at Stony Brook University, has traveled the world observing animals in the wild, including elephants, dolphins, wolves and albatrosses, and says the more he sees, the more he is convinced that many animals experience love in the same way humans do.

Wolves are a particular passion.

“Wolves will spend a lot of energy trying to attract a specific wolf, and they form a bond that will last all their lives,” he said. “I’ve never heard of a wolf abandoning his children. They appear to have relationships more durable than humans who have divorce.”

Dr. Thomas says that when a new coalition of male lions takes control of a pride, the first thing they will try to do is kill all the young cubs that are still nursing.

“They’re eliminating a competitor’s genes from making it into the future,” he says. “But also it causes a cub’s mother to come back into estrus so that the new male can breed with the females sooner.”

As for elephants, the Temptations’ classic “Papa Was a Rolling Stone” applies.

“The female is receptive for four days every four years,” Mr. Safina says. “The male chases around the female, who runs away, but wants to be caught. They run side by side and eventually he lays his trunk along her back, as if they were playing tag. Once he does that, she stops, adopts a receptive position and the male mounts her.”

In less than a minute, he’s done, and skulks off into the brush in search of another female who is willing to spend a minute with him.

“They just look for females in estrus, mate with them, and that’s all they have to do with the females and the babies,” Mr. Safina said.

Of course there are plenty of men who behave like elephants. “There’s sex without bonding in humans and other animals,” he said. “Is there any romance in a one-night stand? Well yes, some, but it’s not very high quality, very deep or long lasting.”

Lions and elephants make male gorillas look like family men. Ernie plays with his babies, and can stop a young gorilla from too much roughhousing just by arching his sagittal crest. The male gorilla will protect the troop if it is threatened, and because female gorillas will leave if they are unhappy, Ernie has an incentive to behave himself.

During Mr. Safina’s tour that day, there was very little contact between the sexes. Two male baboons were eating ticks and bugs off each other’s backs. The big cats paced, alone. Two radiated turtles touched noses, but that was all.

And Ernie spent the afternoon behind a rock, out of sight. Asked what it all meant, Mr. Safina looked stymied, but only for a moment. “It would suggest romantic love is a very rare thing,” he said.