For the initial experiment, 21 females gained access to an aspartame-sweetened ethanol concoction during a group "happy hour." Neck collars registered the amount of fluid consumed, and each monkey received a blood alcohol level test at the end of the period.
In a follow-up experiment, 10 monkeys were housed individually during the "happy hour."
"The singly housed monkeys certainly drank more than the socially housed monkeys- at least two to three-fold more," Chen told Animal Planet News. "With the socially housed monkeys, there are a number of factors that can potentially compete with access to alcohol, such as social status or dominance ranking."
Lower-ranked monkeys and males tended to drink more overall, but certain individuals consistently drank more than others, regardless of status or housing conditions.
"Similar to humans, rhesus macaques have individual differences in taste preference, stress levels, drug tolerance and genetic background that lead to differences in alcohol intake," explained Chen.
In yet another study, the scientists gave a group of male monkeys 24-hour access to the beverage dispensers. According to the researchers, a spike in consumption immediately followed the facility’s working hours.
"Like humans, monkeys are more likely to drink after stressful periods, such as soon after the daily 8-5 testing hours and after a long week of testing," said Chen.
Judy Cameron, a professor and senior scientist at Oregon Health & Science University, told Animal Planet News, "The fact that different animals consume very different amounts of ethanol suggests that the neural systems in the brain that govern alcohol consumption differ in macaques as they do in humans."
"Monkeys show highly individual responses in their choice to drink alcohol excessively," agreed Kathleen Grant, a senior scientist at the Oregon National Primate Research Center. "There are important parallels to human alcoholism."
Since the monkeys appeared to go through withdrawal, Chen and his team hope to investigate drugs that may help prevent related symptoms, which often result in relapse in human alcoholics.
Name: Rhesus Macaque (
Macaca mulatta)
Primary Classification: Cercopithecidae (Old World Monkeys)
Location: Northern India, Nepal, Bhutan, Assam, Bangladesh and northern Pakistan.
Habitat: Forest edges, open areas, villages, towns, temples, railway stations and ruins.
Diet: Insects, shoots, fruits, seeds, cultivated crops and small animals.
Size: From 17 to 24 inches in length, and six to 13 lbs in weight.
Description: Olive brown with orange-red fur on the loins and rumps; thick build compared to other macaques.
Cool Facts: A single troop can consist of up to 100 individuals, all of which are under the leadership of a single dominant male; these troops can have smaller subgroups, each under a different male.
Conservation Status: Lower Risk (Near Threatened)
Major Threat(s): Habitat loss and poaching.
What Can I Do?: Visit
American Society of Primatologists for information on how you can help.
