Animals of Some Species Form Lasting Friendships With One Another
The Value of Friendship
Scientists have long known that people who have a good social network live longer, healthier lives than people who have not developed social contacts. Researchers at Brigham Young University have combined and analyzed data from 148 different studies of the connection between social interactions and a person's health. The studies involved more than 300,000 people. Their results, published in the summer of 2010, showed a much more dramatic effect of social relationships on health than was previously thought. For example, the researchers equate a poor social network with the negative effect of smoking 15 cigarettes a day, and consider it to be twice as dangerous as obesity. On the positive side, other studies have indicated that people who have a highly developed social network have lower levels of stress hormones, lower blood pressure and stronger immune systems than those without good social ties.
Now, in the February 20, 2012 issue of "Time" magazine, author Carl Zimmer talks about how different animal species--dolphins, chimpanzees, baboons and others--form friends in the same way that people do, and these friendships lead to the same kinds of health benefits experienced by humans.
Over the course of 40 years, biologist Randall Wells studied bottlenose dolphins in the Sarasota Bay in Florida. He observed two distinct patterns of friendship formation--one for males and one for females. A young male dolphin will pair up with another, unrelated male, and the two will swim together for considerable periods of time during the day. This "friendship" lasts for years, and if one member of the pair dies, the other will swim alone for several months, as if in mourning. Young female dolphins, however, do not restrict their association to any particular unrelated female. During their reproductive years, the females circulate from one group to another. It is not until later in life that female dolphins form lasting associations with one or two other females. For example, Wells and his associates witnessed three older females hunting for food together and keeping company with one another by swimming closely together for quite some time during the day.
Baboons form social relationships, and these relationships lead to important health benefits in the same way that humans derive benefits from their social networks. Anthropologist Joan Silk studied baboons in Kenya and other places in Africa over a long period of time, and found that some females had strong social ties to other unrelated females. These ties endured for many years. The offspring from these females were more likely to survive relative to the offspring from females that did not have any strong social ties. In addition, female baboons with strong social ties were four times more likely to survive to age 15 relative to females that did not have a well-developed social network. Primatologist Robert Seyfarth examined the relationship between glucocorticoid or stress hormone levels and social networking. He found that when baboons experience the loss of a family member, their stress hormone levels go up. In order to make up for the loss, the baboons forge friendships with other baboons. As these friendships develop, stress hormone levels return to normal.
Elissa Cameron of the University of Tasmania in New Zealand observed a group of wild horses dwelling in a mountainous region. Over the course of four years, she observed that certain unrelated mares would pair up and establish a friendship that persisted during the entire period of the study. Cameron was able to correlate reproductive abliity with strength of social network for a given mare. She found that the number of foals a mare could produce increased as the mare's social circle widened.
Chimpanzees are capable of exhibiting the kind of behavior that humans would call friendship. Primatologist John Mitani studied a group of 160 chimpanzees in the forests of Uganda. During his 17-year observation period, he picked out a pair of males that developed a special bond. They would hunt together and share the kill with each other, and they roamed through the forest side by side throughout the day. They defended each other in altercations with other animals. After several years, one of them died. The surviving chimpanzee transformed from a gregarious animal into a recluse. He remained alone for several weeks as if to mourn the death of his friend.
A Word About Dogs
You might think that man's best friend, the dog, would also form friendships with his own kind. Scientists believe that dogs don't exhibit the kinds of behavior toward one another that is characteristic of true friendship--sharing, defending each other and sticking together for a long period of time. This may be because dogs are related to wolves, and there is no friendship in a wolf pack.