Sylvia had everything going for her.
At 23, she held a very high rank in her group of 80 and had all the companionship she needed in her daughter Sierra.
Then one day in the Okavango Delta of Botswana, Sierra was killed by a lion.
Sylvia had simultaneously lost her best friend and grooming partner, and her glucocorticoid stress hormone levels went through the roof.
"Sylvia's stress hormone levels tripled from what they were before Sierra died," Anne Engh of the University of Pennsylvania told LiveScience.
Stressed out and stuck in a depressive, lonely funk, Sylvia the baboon, previously considered the "queen of mean" among her troop, reached out to other baboons for comfort.
"Without Sierra, Sylvia really had nobody else," Engh said. "So great was her need for social bonding that Sylvia began grooming with a female of much lower status, behavior that would otherwise be beneath her."
After a month of grooming and hanging out with her new friends, Sylvia's hormone levels returned to normal. Grooming, the friendly cleaning of each other's fur, is the primary way baboons strengthen social bonds.
The leading cause of death in adult baboons is predation, usually from leopards and lions. Although close friends and relatives of the deceased individual exhibit the highest levels of stress after a killing, the rest of the group feels it too. Increased grooming and interaction is a good way for them to return to normal.
"Like humans, baboons seem to rely on friendly relationships to help them cope with stressful situations," Engh said.
However, while humans actually miss deceased friends, baboons like Sylvia might actually be more stressed about the loss of physical contact with other monkeys and not being clean.
"It could be less that they miss their friends and more of a physiological response to a lack of physical contact and grooming," Engh said.
This study, announced today, is detailed online by the Proceedings of the Royal Society of Biological Sciences.
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