Vanara although popularly translated as monkey can not possibly be monkey.
When the vimana touched down, Bharata, for whom truth was his valour,
happily approached Rama and greeted him again. Kakustha had seen him
after a long time. Full of joy, he made Bharata rise, embraced him and
placed him on his lap. The scorcher of enemies, Bharata, then happily
approached Lakshmana and Vaidehi, greeted them and announced his name.
Kaikeyee's son also embraced Sugriva, Jambavat, Angada, Mainda,
Dvivida, Nila and Rishava. The apes, who could assume any form at
will, assumed human forms.
Ramayana, Yuddha Kanda, Chapter 6(115) translated by Bibek Debroy
No monkey that is currently known to man is capable of changing his form.