Apes have excellent memories.
Apes have fantastic memories and can recall old faces
Researchers have found that the primates are able to recognise photos of friends and family that they have not seen for 25 years.
The experts used infra-red eye-tracking cameras to record where the apes gazed when shown side-by-side images of other bonobos and chimps.
One picture was of a stranger, while the other was of an animal that they had lived with for a year or more at some point during their life.
It was found that the apes' eyes lingered for far longer on images of those with whom they had previously lived, hinting at some ability of recognition.
In one case, a bonobo called Louise had not seen her sister or nephew for 26 years but her eyes honed in on the pair after being shown the images.
Dr. Laura Lewis, from the University of California, Berkeley, said: "These animals have a rich recognition of each other. We don't know exactly what the representation looks like, but we know that it lasts for years.
"This study is showing us not how different we are from other apes, but how similar we are to them and how similar they are to us."