A new study of giraffes in Tanzania has demonstrated that adult female giraffes who spend time in larger groups with other females live longer than less sociable individuals. The effects of sociability on survival even outweigh other factors such as environment or human presence.
Backstory: Study of a giraffe population in Tanzania
For the past decade the research team has been conducting the largest study to date of a giraffe population. The vast scale of their study area in the Tarangire region of Tanzania spans more than a thousand square kilometers and includes multiple social communities, each with about 60 to 90 adult female members. Thus, the study was able to disentangle individual from community-level influences on survival. The study is also unique in combining social network analysis and modeling of vital rates such as survival in a sample of hundreds of individuals.
Study Results Overview
Gregariousness leads to better survival
Giraffe group formations are dynamic and change throughout the day, but adult females maintain many specific friendships over the long term.
“Grouping with more females, called gregariousness, is correlated with better survival of female giraffes, even as group membership is frequently changing. This aspect of giraffe sociability is even more important than attributes of their non-social environment such as vegetation and nearness to human settlements.”
-Dr. Monica Bond, research associate, the Department of Evolutionary Biology and Environmental Studies of the University of Zurich (UZH)
The benefits of many friends
Aside from poaching, the main causes of adult female giraffe mortality are likely to be disease, stress or malnutrition, all of which are interconnected stressors.
“Social relationships can improve foraging efficiency, and help manage intraspecific competition, predation, disease risk and psychosocial stress.”
-Dr, Barbara König, senior author of the study and UZH professor
Female giraffes may seek out and join together with an optimal number of other females in order to share and obtain information about the highest-quality food sources. Other benefits to living in larger groups might be lowering stress levels by reducing harassment from males, cooperating in caring for young, or simply experiencing physiological benefits by being around familiar females. The study also finds that females living closer to towns had lower survival rates, possibly due to poaching.
Social habits similar to humans and primates
The team documented the social behaviors of the wild free-ranging giraffes using network analysis algorithms similar to those used by big-data social media platforms. According to the results, the giraffes are surprisingly similar in their social habits to humans and other primates, for whom greater social connectedness offers more opportunities. Chimpanzees and gorillas, for example, live in communities where ties between many individuals facilitate the flexibility of feeding strategies.
Journal Reference: M. L. Bond, D. E. Lee, D. R. Farine, A. Ozgul, and B. König. Sociability increases survival of adult female giraffes. Proceeding of the Royal Society B, 10 February 2021 DOI: 10.1098/rspb.2020.2770