Bilbo the lemur has developed the habit of travelling to work on the metro with his handler.
He gets on the train with Veronica Lindberg in the northern suburb of Alvik. But Bilbo, who is not really really a morning lemur, tends to stay wrapped inside a handkerchief under her jacket until they have travelled eight stops down the line to Central Station.
By then he is ready to climb out of Lindberg's clothing and onto her head as they prepare for the last leg of the journey to Skansen
"He should really be hanging in his mother's pelt. My hair is probably similar to pelt and he has a great view of what's going on from the top of my head," she told news agency TT.
Despite being almost two months old, Bilbo is still just the size of a man's hand and weighs less than a cell phone:
Rejected by his mother at birth is, he is now out of danger but his handlers are struggling to get his parents to accept him.
"Bilbo is confused. He probably doesn't know he is a bamboo lemur and thinks I am his mother," said Lindberg, a 26-year-old handler at the aquarium.
Lindberg has devoted the past six weeks, night and day, to the little creature that has not left her side since he was born. She feeds him, carries him, gives him all the affection he needs and has even brought him home to her apartment.
Saving a bamboo lemur rejected at birth is a major feat, not least because of the problems posed by feeding it.
"During the first seven days I fed him every hour, night and day," she told AFP.
"We started with only baby formula the first week, then we gave him a mixture of formula and cat milk," she said, adding that he is now also eating pellets.
Bilbo is not yet entirely weaned but he is healthy, growing everyday, said Lindberg, who admitted that she is increasingly fearing the moment the two will have to be separated.
"The separation will probably be harder for me than for him," she said with a laugh.
The tiny creature is one of only about 25 bamboo lemurs living in captivity in the world. Originally from Madagascar, bamboo lemurs -- who eat bamboo, hence their name -- are the smallest species of lemurs.
As adults, these four-legged primates with small snouts, soft brown woolly fur, small ears and long fuzzy tails, usually between 500 and 700 grams, and at most one kilo.
They live for 15 to 20 years on average.
Swedish media went crazy for the rare animal when news of his birth and rejection by his mother became known last week. Bilbo's picture has since been spread across the Internet, rivalling him in the Swedish media with Knut, the more famous polar bear recently born at Berlin's zoo.
Since his birth on February 22, Bilbo has tripled in size to measure 30 centimeters (12 inches) including his tail, and his weight has increased from 30 grams (1.05 ounces) to 170 grams (6.0 ounces).
The aquarium's animal handlers are confident that he has passed the critical stage and no longer worry about his survival. Now they are trying to figure out how to get his parents to accept him.
"Everything has worked much better than expected. The major risks are behind us but now comes another sensitive step," explained Bo Jonsson, mammals curator at Skansen-Akvariet.
Bilbo is not yet aware that he is a lemur and that this is not the normal situation, Jonsson said. "But he will become more and more aware as his instincts develop."
If he fails to bond with other lemurs, he could become aggressive.
"He won't be very dangerous to us because even when he is an adult he will only weigh around one kilo (2.2 pounds)," said Jonsson.
But the Skansen-Akvariet team wants to make sure Bilbo does not take on human ways.
They hope to integrate him quickly, as soon as he is weaned. The longer it takes "the more difficult it can be to reintroduce him in captivity," Jonsson
Whether or not Bilbo can be reintegrated into his own family remains to be seen. His mother Prune is still aggressive toward her offspring and Bilbo cannot be placed in the same cage for the time being.
This kind of "rejection is not common but it's not rare either," said Jonsson.
Bilbo has seen his parents around 10 times since he was born and each time he has looked around curiously, "but he doesn't really understand the situation," Lindberg said.
He has not yet been introduced into the cage, "because we don't know if his parents may kill him," she said.
Jonsson said the Skansen-Akvariet team would first try to reacquaint Bilbo with his father, who has shown interest in him when handlers have held him up to the glass window of the lemur cage.
If that goes well, then an attempt will be made with the mother.
But if those efforts fail Bilbo may have to be sent to another zoo, possibly in France which has four or five bamboo lemurs.
"We don't want to give him up. But if it doesn't work with his own parents we will try to find another lemur for Bilbo to grow up with," Jonsson said.