The alligator, which is 25 inches long, was discovered under an escalator by a maintenance worker on the lower level of Terminal 3 on Nov. 1, police said.
Chicago Police contained the alligator in a trash receptacle, and the Chicago Herpetological Society took custody, police said.
The alligator was in poor health when it was found and the Herpetological Society planned to ship it to an out-of-state facility once it was rehabbed, CHS president Jason Hood said when the animal was initially discovered.
"It is very lucky to have been spotted and captured before the weather killed it," Hood said at the time.
But the alligator "is still not eating and is extremely stressed," Hood said in a statement Friday. There is no interaction with the alligator except for feeding attempts and to check its cage while the society works to get the animal "back into the best health possible."
A woman was seen carrying a baby alligator on a CTA train at 1:15 a.m. on November 1. CTA officials say the woman boarded the Blue Line at the Pulaski stop and headed to O'Hare. She didn't make any efforts to conceal her alligator, as a matter of fact, in the surveillance pictures, it looks as though she was showing it off to passengers.
Surveillance pictures show her on a Blue Line train, and according to investigators, getting off the train at O'Hare.
Photos captured the woman dressed in all black riding the Blue Line headed to O'Hare like any other passenger, until she pulls put a two-foot-long alligator. At one point, she sits down holding a phone in one hand and the gator in the other. The last image provided by the CTA shows her making absolutely no effort to hide her pet.
"She was definitely holding it up so passengers were able to take a look at it and even snap a few photos, which is how they wound up on social media," said Lambrini Lukidis, CTA spokesperson.
The transit agency was alerted about a reptile on board after a picture appeared on Twitter. CTA officials believe the same alligator was abandoned at O'Hare.
CTA cameras show the lady in black with the alligator arriving at O'Hare. She is seen again, a few minutes later, leaving without her cold-blooded friend. Dumping the gator is a crime.
"It is a misdemeanor to leave the animal unattended, so in this case, it appears as though that is what happened," said Lukidis.
If you have any information about the woman seen in the surveillance pictures, please contact the CTA or Chicago Police.
The Sun-Times Media Wire contributed to this report.