He approached slowly, hesitantly.

Tino the silverback had lived with Muke, a fellow Western Lowlands gorilla, for more than a decade. And though she often was cool to his attention-seeking antics, she always at least acknowledged his presence.

Now, as the great black beast sauntered into the room, Muke was still. And Tino didn't seem to know how to react.

Staff members at Utah's Hogle Zoo believe Tino understood that Muke, suffering from cancer for more than a year, had been ill. Preparing for her death, they introduced him to new acquaintances -- a small gang of guenon monkeys -- over the past year.

But they also suspected it would be difficult for Tino to come to terms with his longtime companion's death. So, after euthanizing Muke on Monday, having decided she was in too much pain, zookeepers invited Tino into the room to visit her one last time.

The act of offering zoo animals a "wake," of sorts, is increasingly common in American zoos, reflecting an improved awareness of the social and psychological needs of captive animals. And in the case of Muke and Tino, it presented Hogle zookeepers with a unique opportunity to see the complex emotional character of a species that is among humanity's closest genetic relatives.

As Tino examined Muke's lifeless body, primate animal care supervisor Andy Henderson watched from a walkway a few feet away.

"He's used to her moving about, acknowledging him as he comes by," Henderson said. "So he looked at her very closely, from about a foot away and then he finally moved closer and slowly sniffed at her."

Tino left the room with little further reaction, only to return a few moments later to repeat the act. "And then," Henderson said, "very gently, he reached out and stroked her leg."

When it comes to apes -- which share about 98 percent of a human's DNA -- the boundaries between science and speculation aren't always clear.

"We do tend to anthropomorphize a little," Henderson said. "We try not to, but especially with an animal like the gorilla, they're so close to humans, it's hard not to."

Still, it's sometimes difficult for those who don't spend a great deal of time with the apes to recognize their emotional temperaments, he said.

"They don't show emotions like humans do, like in facial expressions," he said. "Gorillas don't smile -- they make a low grumbling sound when they're happy."

But to understand gorilla emotions, human feelings are not a bad starting point, said Penny Patterson, founder of the California-based Gorilla Foundation.

"Darwin spoke of the emotions of man and other animals," said Patterson, who is best known for her work with Koko the gorilla, whose sign language vocabulary reportedly includes about 1,000 words. "We don't tend to think along those lines, that humans are just another line of animal that evolved alongside other primates, but that's how we evolved -- and that's how our emotions evolved."

Although they may express them differently, Patterson said, gorillas experience a range of emotions similar to those of humans. And as for humans, she said, one of the most powerful emotions gorillas experience is grief.

When Koko's longtime companion, Michael, died in 2000, "Koko was just totally inconsolable," Patterson said. "She was definitely in mourning, like the rest of us."

In August, when a 3-month-old gorilla named Claudio died suddenly at Germany's Munster Zoo, his mother Gana seemed incapable of accepting the loss. She cradled the limp body in her arms, sporadically shaking him and stroking his fur, until keepers took the dead infant five days later.

The spectacle -- and heart-rending photos that came of it -- prompted international discussion about the emotional similarities between human and other animals.

Zoo director Joerg Adler told The Daily Mail of London that many of his patrons were "incredibly shocked," but he noted that they were witnessing something that would be quite common outside of captivity.

"This, perhaps, is one of the greatest gifts that a zoo can bestow," he said. "To show animals are very much like ourselves, and feel elation and pain."

mlaplante@sltrib.com