Footage emerged Wednesday of a dying chimpanzee becoming emotional at the sight of her old friend at the Royal Burgers Zoo in Arnhem, the Netherlands. Mama, a 59-year-old ape, had refused food from her caretakers and remained unresponsive until she spotted Professor Jan van Hooff. The pair first became acquainted in 1972. 

The video was first published in May 2016, but its managed to gain viral traction Wednesday. Mama is curled up in a ball in the footage as she lies on top of hay, with a sad expression worn across her face. Professor van Hooff arrived at the zoo and began to rub her as he attempted to feed her food. Mama didn't immediately recognize van Hooff, but she appeared to smile as she touched his face.  

Mama died a week after seeing her friend. 

A representative for Professor Jan van Hooff did not immediately return International Business Times' request for comment. 

Professor van Hooff, who taught behavioral biology at Utrecht University in the Netherlands, co-founded Mama's chimp colony at Royal Burgers Zoo. Mama was originally born in the wild, but she was the first-ever chimpanzee to be raised at the zoo, the Independent reported Wednesday. Mama is said to have "played an important social role in the colony," according to the video's description on YouTube. 

Mama isn't the only ape to have recognized an old friend. Actor Robin Williams befriended a Gorilla named Koko, who communicates in sign language, during the filming of a public service announcement for The Gorilla Foundation in 2001. The news of Williams' death reportedly caused Koko to become "very somber, with her head bowed and her lip quivering," according to a press release published on in 2014. 

A tribute video for Williams, which featured Koko, was shared by the ape's team to YouTube

Chimpanzees are very similar to humans. The endangered species is very sociable, like human beings. Chimpanzees also care for their offspring for years and they have the ability to live to be more than 50 years old, the World Wildlife Fund shared on its website. The ape serves as humans closest cousins because we share 98 percent of our genes.

"Humans, chimps and bonobos descended from a single ancestor species that lived six or seven million years ago," the American Museum of Natural History (AMNH) wrote to its website. "As humans and chimps gradually evolved from a common ancestor, their DNA, passed from generation to generation, changed too. In fact, many of these DNA changes led to differences between human and chimp appearance and behavior."

Chimpanzees are said to have better short-term memory than humans, research suggests. Researchers from Kyoto University's Primate Research Institute in Japan studied 14 chimpanzee's minds, and their ability to process information at a quick pace. A video taken of the lab test showcased an ape, Ayumu, in front of a computer with numbers one through nine displayed across the screen.

As the numbers quickly vanished, the chimpanzee was required to rely upon its memory to place the numbers in numerical order. The ape managed to quickly ace the test repeatedly. 

"Chimps are living in the world of here and now," Professor Tetsuro Matsuzawa, the study's lead researcher, told the Toronto Star in 2013. "We are living in the world, thinking about the past, thinking about the future, trying to understand the meaning of what we see, and bringing the information back to friends and families and colleagues to share the experience."