A Goodfellow's tree kangaroo joey pops its head out of its mother's pouch in the Singapore Zoo in Singapore on July 28, 2020. The Goodfellow's tree kangaroo joey was born in the Singapore Zoo on Feb. 4 this year. (Xinhua/Then Chih Wey)

A Goodfellow's tree kangaroo joey pops its head out of its mother's pouch in the Singapore Zoo in Singapore on July 28, 2020. The Goodfellow's tree kangaroo joey was born in the Singapore Zoo on Feb. 4 this year. (Xinhua/Then Chih Wey)

A Goodfellow's tree kangaroo joey pops its head out of its mother's pouch in the Singapore Zoo in Singapore on July 28, 2020. The Goodfellow's tree kangaroo joey was born in the Singapore Zoo on Feb. 4 this year. (Xinhua/Then Chih Wey)

A Goodfellow's tree kangaroo joey pops its head out of its mother's pouch in the Singapore Zoo in Singapore on July 28, 2020. The Goodfellow's tree kangaroo joey was born in the Singapore Zoo on Feb. 4 this year. (Xinhua/Then Chih Wey)