A group of researchers conducting an observational study on a group of marmosets in Brazil describe in detail the compassionate caretaking behavior of a dominant male toward a dying dominant female, which is thought to be exceedingly rare in the animal kingdom. The observations have been published in the journal Primates.
Animals respond to the death of other individuals in a variety of ways; eating or burying the body is common, but a few species display more complex behaviors. Chimpanzees in particular have been the focus of many studies because they display compassionate caretaking behaviors toward dying group members, which had only previously been observed in humans. In this report, researchers further the knowledge of this field by describing for the first time the behavior of a wild New World male monkey to a dying female.
Researchers have been observing a group of 12 common marmosets (Callithrix jacchus) in a forest in northeast Brazil since 2001. The group consisted of 4 adult males, 3 adult females, 3 juveniles and 2 infants. In a very unfortunate series of events, the dominant female of the group (termed F1B) fell from a tree and sustained a traumatic injury to her head and body. When the dominant male (termed M1B) noticed the female dying in agony, he left the infants he was carrying in a tree and immediately went to her. He then displayed a series of behaviors that astounded the researchers.
The male showed he was protective of the female by scanning the area and issuing calls of alarm, which are usually only uttered when predators are spotted. Whenever any members of the group tried to approach, he displayed aggressive postures to deter them. At times the male also made attempts at copulation, which could be because marmosets commonly use sex to reinforce social bonds.
He also embraced her, sniffed her and watched her for periods of up to 20 minutes whilst she was dying. These caretaking behaviors may suggest compassion, and probably occurred because of the social status of the pair within the group and the fact that the pair had been bonded for at least 3.5 years, which is around a third of their total lifespan. The couple had also produced 8 offspring.
Approximately three months after F1B’s heartbreaking demise, M1B left the group and was not seen again.
Taken together, these surprising observations suggest that compassionate-caretaking behaviors toward dying group members in non-human primates may not be restricted to chimpanzees as previously believed.
The incident was recorded by the team, and a shortened version can be viewed in the YouTube video below. As a warning, it is pretty upsetting toward the end.