On Nov. 16, Chicago's Lincoln Park Zoo welcomed a newborn Western lowland gorilla. She was the first of the endangered species to be born at the zoo since 2005, and appeared to be doing well. Nine days later, the baby gorilla, who hadn't even been named yet, was found dead. Here, a brief guide to her "mysterious" death:

What happened?
Zoo keepers found the baby gorilla's mother, Bana, a a 16-year-old first-time mother, carrying her 9-day-old child's lifeless body around their enclosure. The zoo allowed Bana to stay with her dead baby for several hours to "make peace with what had happened." Staff at the Lincoln Park Zoo note that they had worked with Bana to help her develop her baby-rearing skills and she appeared to be a "good and willing mother."

So how did the baby gorilla die?
A preliminary exam shows that the baby died from a head trauma and skull fracture. "There are no bite marks or cuts and no sign of aggression, but it is possible she may have been dropped or even sat on," says a zoo spokeswoman. If Bana killed her baby, it was most likely an accident. It happened at night when there was insufficient light for the incident to be recorded clearly by the zoo's video cameras.

Have gorillas been known to kill their infants intentionally?
Yes. Just two out of three gorilla infants survive, and the complex dynamics of gorilla tribes aren't well understood. This past May, a 7-month-old baby gorilla at the London Zoo was killed after a scuffle broke out when a male silverback was introduced to the infant and his mother. In 2010, a little gorilla at the Louisville Zoo lost part of his leg in a family skirmish. In the wild, infanticide typically occurs when the dominant male gorilla dies and mother and baby look to other gorilla groups for protection "rather than face the potential of a rival male murdering the deceased male's offspring," says the Christian Science Monitor.

Sources: BBC News, Christian Science Monitor, Daily Mail, USA Today