Now they finally have their answer — it's a girl.
Researchers have had a hard time identifying the sex of Patty, named after long-time zoo supporter Patty Meyers, since her Oct. 11 birth because the baby's mother, Bana, had been holding her so tightly in her arms.
"That's a happy reason for the delay," wrote zoo president Kevin Bell in an announcement. "Bana has been an attentive, nurturing mother, and the rest of the gorilla group — while curious — has given mom and baby the space they need to bond and thrive."
Bana gave birth to Patty, her second baby, when she was 17 years old, making her the 51st gorilla born at the Lincoln Park Zoo. Her first baby died in November 2011 because of accidental head trauma, according to the zoo. The death of Bana's first baby occurred over night in the dark, and scientists at the zoo are still unsure what happened.
"We are seeing excellent maternal care from Bana," said Michael Brown-Palsgrove, Zoological Manager of Primates. "We are feeling very positive."
She’s been the sole caregiver in terms of handling and holding the baby, Brown-Palsgrove said.
Caregivers at the zoo hope Bana's mothering skills wear off on 6-year-old female Susie.
"It’s most important for her to see the baby," Brown-Palsgrove said. "Hopefully one day she can have a baby of her own."
Scientists have not examined the baby gorilla yet, and are unsure of her size and weight. One thing they are sure about, is that she is growing steadily and has shown visible signs of maturing, according to Brown-Palsgrove.
The newborn has apparently given Bana a boost in social status among the other gorillas.
"It is common for female adult gorillas with a new infant to ascend the social hierarchy when they have a baby," said Maureen Leahy, the zoo's curator of primates.
Scientists have noticed that since Patty's birth, Bana has begun using touch-screens used for research, something she had never done before.
"Before she would defer as higher-ranking members monopolized the touch-screens," Bell said. "Now she seems secure in moving up to explore them herself."
Visitors can see Bana and Patty at the Regenstein Center for African Apes from 10 a.m. to 4:30 p.m. each day.