A judge has dismissed a lawsuit against Bronx Zoo that sought to declare an Asian elephant named Happy a person with a right to be free.
They wanted Happy to be released from the zoo where she has lived for the past 50 years.
In a study published in 2016 in the journal Science, researchers described Happy's ability to recognise herself in a mirror as evidence of human-like self-awareness.
Nonhuman Rights Project used the report to argue Happy was not a thing lacking rights but akin to a person with a fundamental right to liberty on the principle of habeas corpus which guards against unlawful detention.
In its petition, the group said: "The central purpose of habeas corpus is to release autonomous beings from illegal imprisonment.
"As an autonomous self-determining nonhuman, Happy is entitled to immediate release from her unlawful imprisonment."
The Wildlife Conservation Society, which runs the Bronx Zo, called the lawsuit "ill-conceived" and defended its care of the elephant.
In a statement, the group said: "We are pleased with the Bronx County Supreme Court's decision today to dismiss the Nonhuman Rights Project's petition. ... In doing so, the court supported the Bronx Zoo's legal position and we believe this decision is in Happy's best interests.
"The Bronx Zoo takes excellent care of Happy and will continue to do so, along with all animals here at the zoo."