Monkeys become cautious after viral outbreak

When a new disease appears, people start cleaning more and avoiding crowds. A similar shift can happen in animals. The 2020 outbreak was deadly. A study in the Royal Society Open Science journal shows that Japanese macaques, or Macaca fuscata, changed how they approached food after a viral outbreak.

In 2020, a primate sanctuary in southern Texas discovered a simian retrovirus Type II. The virus can cause AIDS-like immunodeficiency. It spreads through bites and scratches. The outbreak caused severe illness and death in some monkeys. The staff separated groups, tested animals, and quarantined the infected.

Researchers compared 55 macaques from three groups that had the outbreak with one group that did not. They offered food on a clean wooden surface and on a surface covered with real macaque feces sealed under clear epoxy. The monkeys could see the feces but could not touch them. A brightly colored kitchen sponge was also used in some trials to check for avoidance of unfamiliar objects.

Behavioral change after outbreak

Monkeys from outbreak groups ate the food on the contaminated surface only 47 percent of the time, compared with 79 percent for the non‑outbreak group. The data suggest a behavioral change. The behavior change was seen even in monkeys that had not been infected. The data suggest that living through the disease, rather than getting sick, made the groups more cautious.

The findings show that the behavioral immune system works in primates as it does in humans. The study also hints that disgust evolved to help animals avoid pathogens. Because monkeys can learn from each other, a cautious attitude could be passed to new group members. Future research may test whether new animals adopt the behavior of an outbreak‑experienced group.