Species Spotlight: The Rhesus Macaque

Mike Ryan, October 27, 2018

Over 70,000 non-human primates are right now being caged in isolation and having some kind of medical testing done on them. Usually this is painful and ends in euthanasia. And 65% of the time, these primates are Rhesus Macaques.

Even though our (human) genome and theirs diverged 25 million years ago, our DNA is 93% similar to that of rhesus macaques. As such, it’s no surprise that they’ve repeatedly demonstrated self-awareness (recognizing themselves in mirrors, for starters), and their minds are impressive: They count, use tools, understand basic rules, demonstrate same/different judgement ability, and overall show complex cognitive abilities. Although lifespans vary based on setting, these herbivores can live as long as 40 years.

There’s no shortage of evidence that in many ways, they’re kinder than the people trapping and performing painful experiments on them: Cruel testing done on these animals ironically showed us how compassionate they are. As noted in 1993 by Carl Sagan and Ann Druyan in Shadows of Forgotten Ancestors, a series of cruel experiments done at Northwestern University in 1964 revealed that rhesus macaques would rather starve than hurt one another. In the experiment, the rhesus macaques could only eat if they first pushed a button to deliver a dangerous and painful electric shock to another macaque, visible through a one-way mirror. Most (87%) of the macaques chose to go without food instead.

Rhesus Macaques live in a wide variety of climates and habitats; Mountains, swamps, tropical forests, dry and semidesert regions—they thrive in any setting.

As a result, rhesus macaques have the largest geographic distribution of any non-human primate. They’re found living in the wild in Afghanistan, India, Thailand, China, Pakistan, Bhutan, Burma, Nepal, Bangladesh, Laos, and Vietnam. There’s even a wild colony of them living in Florida, which is a result of one man’s bizarre decision to release them in the wild years ago.

When they’re not housed in cruel isolation in the basements of testing facilities, they naturally form strong matriarchal hierarchical social groups that have multi-generational bonds. Families of rhesus macaques will often have in it a mother, grandmother, great-grandmother all present in the same group. One unique trait to rhesus macaques is that the youngest females tend to outrank the older females in a group.

They’re enormously social, and grooming plays a big role in their social relations.  This process of combing (with fingers) the coat of another macaque helps remove parasites, sure, but it’s also a relaxing experience for the one being groomed and goodwill is created as a result. The signal for wanting to be groomed? Often a smack of the lips!

Despite speculation to the contrary, there’s no particular meaning to the word “Rhesus”. The French artist and naturalist Jean-Baptiste Audebert chose the “Rhesus” name, but said the name had no meaning. Today, the word “rhesus” may as well mean “victim” given that tens of thousands of them right now are suffering in cruel isolation in cement cages, locked in basements. And all to be a footnote in someone’s study.

The saddest example of how we’ve abused these relatives of ours is the work of Harry Harlow, whose experiments on maternal deprivation were so extreme that even his colleagues blew the whistle on his methods.

Primates used in testing is at an all time high yet the number of Americans in favor of animal testing is in decline. Learn more about what this means for animals and what you can do about it on our blog.