Baby Tree Kangaroo At The Bronx Zoo Makes Its Debut Appearance Exciting news over at the Bronx Zoo with the first appearance of a 7-month-old tree kangaroo peeking out of its mother’s pouch. The baby Matschie’s tree kangaroo was born in December, but at birth, Joey’s are only the size of a human thumbnail and immediately crawl into their mother’s pouch. On average, it takes a baby kangaroo seven months to emerge from their mother’s pouch where majority of its physical development happens, so the baby is right on time!