This video is called baby spider monkey.
From the Earth Times:
Mexico City – A female spider monkey has adopted as its offspring a Syrian rat at a zoo in the eastern Mexican city of Veracruz, in a behaviour that experts have termed a “psychological maternity” derived from hormonal disorders, Mexican media reported Wednesday. Photographs published in the daily La Jornada show the monkey named Pancha with the little rat in its arms. The rat left the place in the zoo where it had been living to move to the area reserved for monkeys.
Pancha does not only hold the rat but also feeds it and picks off parasites on the rat. The relationship has become a sensation at the Miguel Angel de Quevedo zoo, some 400 kilometres east of Mexico City.
Zoo director Rafael Mariano Torres was quoted in Veracruz media as saying that visitors first discovered the phenomenon on Sunday, when they saw Pancha holding the rat on her lap.