Jambavan the name does not suggest a bear, because his daughter was one of the queens of Dvaraka married by Krsna. Just like sometimes our name is Krsna, that does not mean that I am real Krsna, but I am Krsna Das or servant of Krsna. From the description of Srimad-Bhagavatam we understand that this Jambavan was very sturdy and strong fighter. Sometimes we get such picture of bodily construction of a black man in your country. So in this way you can guess what should be the features of his body. But certainly he was not a bear.
Letter to Jadurani, Bharadraja, and Muralidhara, 4 June, 1970